Technical Memorandum No. 8140-CC-2004-1

Technical Memorandum No. 8140-CC-2004-1

Corrosion Considerations for
Buried Metallic Water Pipe

United States Department of the Interior
Bureau of Reclamation
Technical Service Center
Denver, Colorado

July 2004

MISSION STATEMENTS
The mission of the Department of the Interior is to protect and provide access to
our Nation’s natural and cultural heritage and honor our trust responsibilities to
Indian tribes and our commitments to island communities.

The mission of the Bureau of Reclamation is to manage, develop, and protect water
and related resources in an environmentally and economically sound manner
in the interest of the American public.

Contents
Page
1.0 Executive Summary ..................................................................................................................1
2.0 Introduction...............................................................................................................................2
2.1 Background ................................................................................................................ 4
2.2 Scope of Review ........................................................................................................ 6
3.0 Corrosion Design ......................................................................................................................7
3.1 Corrosion by Soils...................................................................................................... 7
3.2 Soil Corrosivity Parameters ....................................................................................... 7
3.3 Corrosive Soil Determination .................................................................................. 10
3.4 Typical Corrosion Mitigation Methods ................................................................... 13
3.4.1 Bare Pipes ............................................................................................... 13
3.4.2 Polyethylene Encasement ....................................................................... 14
3.4.3 Bonded Dielectric Coatings .................................................................... 14
3.4.4 Cement Mortar Coatings ......................................................................... 15
3.4.5 Corrosion Monitoring Systems ............................................................... 15
3.4.6 Cathodic Protection Systems .................................................................. 15
4.0 Buried Steel and Ductile Iron Pipe .........................................................................................16
4.1 Corrosion Mitigation for Ductile Iron Pipe ............................................................. 16
4.1.1 Effectiveness of Polyethylene Encasement on Ductile Iron Pipe ........... 18
4.1.2 Peer Review of Reclamation’s Evaluation of PE Encasement
for Ductile Iron Pipe ............................................................................ 21
4.2 Corrosion Mitigation for Steel Pipe ......................................................................... 22
4.3 Corrosion Prevention Criteria .................................................................................. 23
4.3.1 Previous Reclamation Guidelines ........................................................... 23
4.3.2 National Industry Standards.................................................................... 23
4.3.3 Water Utilities Criteria ............................................................................ 25
4.4 Historical Performance ............................................................................................ 31
4.4.1 Summary of Reports and Data Reviewed ............................................... 31
4.4.2 Interpretation of Historical Performance Data Reviewed ....................... 33
4.4.3 Historical Performance Conclusions....................................................... 33
4.5 Expected Service Life .............................................................................................. 35
4.5.1 Reclamation Information on Expected Service Life ............................... 35
4.5.2 Literature Review on Expected Service Life .......................................... 35
4.5.3 Conclusions on Expected Service Life ................................................... 36
4.6 Life Cycle Costs ....................................................................................................... 37
4.6.1 General .................................................................................................... 37
4.6.2 Impact on Bid Prices ............................................................................... 39
4.6.3 Life Cycle Cathodic Protection Costs ..................................................... 40
4.7 Peer Review of Reclamation Corrosion Protection Strategy ................................... 41

i

Page
5.0 Buried Concrete Pipe with Steel Reinforcement ....................................................................42
6.0 Recommendations...................................................................................................................44
6.1 Corrosion Provisions................................................................................................ 44
6.2 Bid Adjustments....................................................................................................... 46
6.3 Updates to the Corrosion Prevention Criteria and Requirements Table .................. 47
7.0 References...............................................................................................................................48
Appendices
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F

Responses to Review Panel Input
“Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”
E-Mail Messages from Mike Woodcock to James Keith
Questions for the Panel and Panel Conclusions
Exterior Coating Cost Analysis
April 2004 Southwest Pipeline Excavation

ii

Corrosion Considerations for Buried Metallic Water Pipe

1.0 EXECUTIVE SUMMARY
Because of corrosion concerns raised relative to the use of cathodic protection and polyethylene
(PE) encasement on ductile iron pipe, Reclamation conducted an extensive evaluation of the
corrosion mitigation alternatives listed in the April 23, 2003, Corrosion Prevention Criteria
and Requirements table (table 1). This study was based on Reclamation’s experience, the
experience of other professionals in the corrosion and pipe industries, a review of pertinent
national standards, and a review of relevant literature.
While much of the review completed during the preparation of this report focused on steel and
ductile iron pipe, the findings resulting from this review have also proven valuable in evaluating
Reclamation’s corrosion protection criteria for concrete pipe with steel reinforcement.
Therefore, the updates to Reclamation’s Corrosion Prevention Criteria and Requirements table
include revised criteria for steel and ductile iron pipe as well as revised criteria for concrete pipe
with steel reinforcement. Other more general changes to the table reflect a move to a more
unified means of corrosion prevention designs for all Reclamation pipelines regardless of the
type of water system.
The study results and the information contained in this report resulted in an updated Corrosion
Prevention Criteria and Requirements table, dated July 2004 (table 2). Application of the
table’s criteria and requirements shall be in accordance with the Reclamation Manual Policy
“Performing Design and Construction Activities” (FAC P03).
The updates to Reclamation’s Corrosion Prevention Criteria and Requirements table are as
follows:
1.

The table title has been changed to reflect that these are minimum corrosion requirements.

2.

The distinction between irrigation pipelines vs. municipal and industrial pipelines has
been removed. The same corrosion prevention criteria and requirements now apply
to all Reclamation pipelines.

3.

The pipe size and weight restrictions for the use of PE encasement on ductile iron
pipe have been removed from the table.

4.

The soil resistivity values for the minimum required corrosion protection measures
for pipelines have been revised:
•

For steel and ductile iron pipe, a bonded dielectric coating and cathodic
protection is required for soil resistivities ≤ 2,000 ohm-cm, an unbonded
coating (PE encasement for ductile iron pipe and cement mortar with coal tar
epoxy for steel pipe) and cathodic protection is the minimum requirement for
soil resistivities between 2,000 and 3,000 ohm-cm, and an unbonded coating
(PE encasement for ductile iron pipe and cement mortar for steel pipe) and
corrosion monitoring is the minimum requirement for soil resistivities
≥ 3,000 ohm-cm.
1

Corrosion Considerations for Buried Metallic Water Pipe

•

For pretensioned concrete pipe, mortar coating with coal tar epoxy and
cathodic protection is required for soil resistivities < 3,000 ohm-cm, and
mortar coating and corrosion monitoring is the minimum requirement for
resistivities ≥ 3,000 ohm-cm.

•

For reinforced concrete pipe, concrete coating with coal tar epoxy and
cathodic protection is required for soil resistivities < 3,000 ohm-cm, and
concrete coating and corrosion monitoring on pipe with steel joint rings is the
minimum requirement for resistivities ≥ 3,000 ohm-cm.

5.

The cutoff point for increased corrosion protection for pretensioned and reinforced
concrete pipe was reduced from 4,000 ohm-cm to 3,000 ohm-cm.

6.

Prestressed concrete pipe has been removed from the table. Reclamation has had a
moratorium on the use of this type of pipe since 1990. If and when this changes,
corrosion mitigation measures for prestressed concrete pipe will be added to this
table.

Based upon the information gathered during the preparation of this report, Reclamation has not
found sufficient cause to conclude there is a significant difference in the performance
expectations for repairs or anticipated service lives of steel or ductile iron pipelines.
The report includes a method of applying an adjustment to the bid prices for buried metallic
pipes based upon operation, maintenance, replacement, and energy (OMR&E) costs for cathodic
protection (CP). Metallic pipe is defined as steel, ductile iron, or any concrete pipe containing
ferrous elements.

2.0 INTRODUCTION
When Reclamation designs or reviews designs for corrosion protection of pipelines, many
factors are considered, including the guidelines in the Corrosion Prevention Criteria and
Requirements table. These guidelines are updated occasionally to reflect the most current and
applicable corrosion design parameters.
Recent questions regarding Reclamation’s corrosion mitigation practices prompted an evaluation
of the corrosion mitigation alternatives listed in the April 23, 2003, table entitled “Corrosion
Prevention Criteria and Requirements” (See table 1). This report analyzes corrosion protection
measures for buried metallic pipes currently used by Reclamation, with special focus on steel
and ductile iron pipe.
Reclamation has had good experience with both steel and ductile iron pipe performance when the
pipes are properly designed, manufactured, and installed. Consequently, Reclamation commonly
specifies multiple pipe options, including steel and ductile iron pipe, for pipeline projects.
2

Table 1
Corrosion Prevention Criteria and Requirements

Pipe Alternative

Ductile Iron

Prestressed
Concrete3
Pretensioned
Concrete

Irrigation

M&I

Corrosion Monitoring
System

Cathodic Protection
System

Polyethylene
encasement1

>15
≤15

>30
≤30

x
x

x

Bonded dielectric2

>10
≤10

>20
≤20

x
x

x

Mortar/coal-tar epoxy

>25
≤25

>50
≤50

x
x

x

Mortar

>20
≤20

>40
≤40

x
x

x

Mortar/coal-tar epoxy

>15
≤15

>30
≤30

x
x

x

Concrete

>20
≤20

>40
≤40

x
x

x

Concrete/coal-tar epoxy

>15
≤15

>30
≤30

x
x

x

Mortar

>20
≤20

>40
≤40

x
x

x

Mortar/coal-tar epoxy

>15
≤15

>30
≤30

x
x

x

Bonded dielectric2

>10
≤10

>20
≤20

x
x

X

External Protection
(Primary/Supplemental)

Reinforced Concrete

Steel

1
2
3

Soil Resistivity – 10% Probability Value
(Σ-m)

Updated April 23, 2003

Applicable to pipe with corrosion allowance, 24-inch inside diameter maximum, and 150 lb/ft maximum.
(NOTE: Given recent pipe industry experience with ductile iron pipe, Reclamation plans to re-examine this provision.)
Bonded directly to metal to be protected.
Reclamation currently has a moratorium on this pipe alternative.

3

Corrosion Considerations for Buried Metallic Water Pipe

The results of this study are incorporated into the latest update to Reclamation’s Corrosion
Prevention Criteria and Requirements table, dated July 2004 (see table 2).

2.1 Background
Reclamation first considered using ductile iron pipe on projects in the mid 1960s. At that time,
Reclamation’s position from a corrosion standpoint was that ductile iron pipe would be treated
the same as steel pipe, except that steel pipe could be coated with either cement mortar or a
bonded dielectric coating (depending on soil conditions), while ductile iron pipe could only be
coated with a bonded dielectric coating.
In the 1970s, Reclamation added PE encasement as an alternative corrosion mitigation method
for ductile iron pipe.
In 1980, Reclamation determined that different corrosion prevention criteria should be applied to
pipelines carrying water for municipal and industrial use versus pipelines used only for
irrigation. The reason for this distinction or “Use Factor” was based upon the fact that irrigation
pipelines were available for maintenance annually, as opposed to municipal and industrial
pipelines which were required to provide uninterrupted service.
In the mid-1980s, a table was developed which outlined corrosion protection criteria for various
types of metallic pipe.
In the early 1990s, Reclamation revised the table for both steel and ductile iron pipe. For steel
pipe, a coating option for mortar encased with coal tar epoxy was added. For ductile iron pipe, a
footnote was added limiting the use of PE encasement on ductile iron pipe to diameters of
24 inches or smaller and weights of 150 pounds per foot or lighter. This limitation was based on
concerns that damage may occur to the PE encasement during the handling and installation of
larger diameter and heavier pipe. The limitation was not based on the inability for larger pipes to
be adequately protected by intact PE encasement. In 2003, Reclamation revised the footnote
adding the following: “NOTE: Given recent pipe industry experience with ductile iron pipe,
Reclamation plans to re-examine this provision.”
Reclamation’s use of ductile iron pipe is somewhat limited. Approximately 30 miles of ductile
iron pipe have been installed on Reclamation-designed projects. The ductile iron pipelines on
Reclamation designed projects were installed beginning in the late 1970s and are 24 inches in
diameter or less.
Additionally, over 300 miles of ductile iron pipe have been installed on non-Reclamation
projects where Reclamation has had oversight responsibilities (projects not designed by
Reclamation). Ductile iron pipelines installed with Reclamation oversight typically have been

4

Table 2
Corrosion Prevention Criteria and Minimum Requirements1

Pipe Alternative

Soil Resistivity – 10% Probability
Value (ohm-cm)

Corrosion Monitoring

Cathodic Protection2

Bonded dielectric3

YES

YES

>2,000 ohm-cm <3,000 ohm-cm

Polyethylene
encasement

YES

YES

≥3,000 ohm-cm

Polyethylene
encasement

YES

NO

<3,000 ohm-cm

Mortar / coal-tar epoxy

YES

YES

≥3,000 ohm-cm

Mortar

YES

NO

<3,000 ohm-cm

Concrete / coal-tar
epoxy

YES

YES

≥3,000 ohm-cm

Concrete

YES4

NO

≤2,000 ohm-cm

Bonded dielectric3

YES

YES

Mortar / coal-tar epoxy

YES

YES

Mortar

YES

NO

≤2,000 ohm-cm
Ductile Iron

Pretensioned Concrete

Reinforced Concrete

>2,000 ohm-cm <3,000 ohm-cm

Steel

≥3,000 ohm-cm
1
2
3
4

Minimum
External Protection
(Primary/Supplemental)

July 2004

This table should be considered to be the minimum corrosion prevention requirements for a pipeline corrosion design. Additional soil
conditions and risk assessment factors should be considered on a case-by-case basis for each specific project.
OMR&E costs for cathodic protection for each pipe type should be evaluated.
Bonded directly to metal to be protected.
Corrosion monitoring is required for concrete pipe with steel joint rings, but not for concrete pipe with concrete joints.

5

Corrosion Considerations for Buried Metallic Water Pipe

installed with PE encasement and CP. To date, Reclamation is unaware of any failure of ductile
iron pipe on a Reclamation-designed project or on a project for which Reclamation has had an
oversight responsibility.
Reclamation’s historical experience with steel pipe is much more extensive than that for ductile
iron pipe. One of the first steel pipe specifications was the construction of a 90-inch diameter
above-ground steel plate siphon for St. Marys River Crossing and a 78-inch diameter aboveground siphon for Halls Coulee on the St. Marys Storage Unit of the Milk River Project,
Montana (Specification No. 361-D, October 20, 1924). Additionally, Reclamation designed
4- to 20-inch diameter buried steel pipes for the South Ogden Distribution System on the
Ogden River Project in Utah (Specification 1420-D, September 11, 1940). Since the 1960s,
Reclamation has designed and installed approximately 320 miles of buried steel pipe. To date,
Reclamation is unaware of any corrosion failures for steel pipe on Reclamation-designed projects
when cathodic protection has been used.
Reclamation’s historical experience with concrete pipe is extensive. Reclamation has designed
concrete pipe diameters ranging from 12 inches up to 252 inches. Reclamation has designed
various types of concrete pipes including, but not limited to, unreinforced drainage, cast in place
reinforced, cylinder, reinforced, pretensioned, lined cylinder prestressed, and prestressed
concrete pipes. One of Reclamation’s earliest uses of concrete pipe was a 10.5-foot-diameter
buried concrete siphon pipe for Stiver Canyon on the North Platte Project issued in 1923 as
Specification No. 419.
This report summarizes Reclamation’s review of these issues and presents the results of
Reclamation’s evaluation of the technical considerations related to corrosion mitigation for
buried metallic pipelines.

2.2 Scope of Review
National standards and corrosion engineering practices were reviewed to compare with current
Reclamation criteria for determining pipeline corrosion protection measures.
Major water utilities were surveyed to determine their experience with steel and ductile iron
pipe, including what current corrosion criteria they use to protect their pipelines.
Historical performance data was reviewed for steel and ductile iron pipe where possible to see if
a failure rate trend for either type of pipe could be predicted.
In 2003, Reclamation’s corrosion engineer completed an extensive literature review of over
150 available industry references related to the effectiveness of PE encasement used as part of a
corrosion control system for ductile iron pipe (see appendix B). The effectiveness of this system

6

Corrosion Considerations for Buried Metallic Water Pipe

has been the subject of debate within the pipeline and corrosion industries for years and results of
engineering studies on the subject differ widely. Reclamation also reviewed available data
regarding the possible use of PE encasement for steel pipe.
Reclamation also executed contracts with two private sector corrosion engineers (CH2M Hill and
Schiff and Associates) as well as a materials scientist with the National Institute of Standards
and Technology (NIST) to conduct an independent technical peer review of the findings of
Reclamation’s corrosion engineer. In addition, a contract was issued with two additional
materials scientists with NIST to serve as independent “referees” to evaluate the three reviewers’
conclusions as well as the preliminary conclusions of Reclamation’s corrosion engineer.

3.0 CORROSION DESIGN
3.1 Corrosion by Soils
Soil is an essentially neutral, aqueous electrolyte; thus, corrosion of ferrous alloys in soil is a
special case of aqueous corrosion. The general cause of corrosion in neutral soil is attributable to
cathodic depolarization or depassivation by the activity of oxygen. In oxygen concentrationpromoted corrosion, the combined effect of oxygen and moisture causes corrosion. The driving
voltage for the corrosion cell is caused by differences in oxygen available to all surfaces. The
conductivity of the soil controls both the intensity and extent of attack. Oxygen concentrations
in the soil are attributable to differences in aeration, salt concentrations, and their effect on
oxygen solubility, soil permeability, and ground-water flow. However, when the oxygen or
moisture is depleted, corrosion will stop. Appendix B of this report includes a detailed
explanation of the corrosion process.

3.2 Soil Corrosivity Parameters
Soil burial is one of the most aggressive exposures encountered by metallic pipelines. The
common corrosion cells experienced underground are pseudogalvanic (oxygen and pH
concentration effects) and electrolysis (stray current corrosion). Soil conductivity governs the
intensity and extent of attack of both electrolytic and pseudogalvanic corrosion. When iron and
steel are exposed to a highly alkaline environment (coated with mortar or encased in concrete),
the potential corrosive effects of the soil are reduced.
Installation of a buried pipeline requires excavation of a trench, preparation of the invert
bedding, installing the pipe, backfilling with special material to support the pipe, and filling the
remainder of the trench to original ground surface. This sequence ensures an abundant supply of
both oxygen and water in the pipe trench. The trench intercepts, collects, and conveys ground
water which may contain dissolved salts. The water level within the pipe trench will fluctuate
with the ground-water supply, which is related to atmospheric precipitation. Oxygen enrichment

7

Corrosion Considerations for Buried Metallic Water Pipe

and cyclic wetting and drying concentrate the ground-water salts within the backfill. Backfilling
with select, free-draining material (e.g., sand and gravel) compounds this effect by creating a
“French drain.”
Thus, soil corrosivity may be increased relative to virgin conditions by virtue of digging a
trench, installing a pipeline, and backfilling. A supply of both water and oxygen is provided for
pseudogalvanic corrosion and, with time, the conductivity increases because of the elevated salt
concentration.
Stray currents are also a common cause of underground pipeline corrosion. For stray current
corrosion, current from a foreign source such as a nearby CP system, electrified railway, or
improperly grounded equipment is required. Current is collected at some surfaces (cathodes) of
the pipeline and discharged from other surfaces (anodes) as the current returns to the originating
source. The metal corrodes at the anodic sites. The extent and intensity of stray current
corrosion are related to the driving voltage of the foreign power supply, the circuit resistance,
the geometrical relationship between the source of earth currents and the pipeline, the axial
resistance of the pipeline, the dielectric properties and continuity of the pipe coating, and the soil
conductivity.
A source of earth currents is required for stray current corrosion. Although the existing sources
of earth currents can be identified by performing route surveys during design data collection,
additional sources could be installed before or after pipe installation. For this reason, stray
current corrosion is always a consideration for buried pipelines. Rubber gasketed, bell and
spigot joints are often used on pipelines in the water industry and often result in a pipeline which
is not electrically continuous, which is a factor to consider for corrosion mitigation. The
electrical continuity across the joint is dependent on the physical contact between the bell and
spigot ends of a joint. If physical contact exists electrical continuity can occur, although without
installation of electrical continuity joint bonds positive continuity is not obtained. An electrically
discontinuous pipeline collects less stay current than an electrically continuous pipeline which
results in less stray current corrosion (Bonds, 1997). However, any current that is collected on
an electrically discontinuous pipeline can cause stray current corrosion when the current leaves
the pipe surface to get around an electrically discontinuous pipe joint.
The vulnerability of metallic pipes to stray current corrosion is dependent on metal surface area,
dielectric properties of the coating, and pipeline continuity.
Another source of corrosion is the lack of isolation between two different types of pipe materials.
This commonly occurs when copper pipes are directly attached to steel or ductile iron pipes
without any isolation. The potential difference between the two materials will lead to
corrosion.
Because the requirement for both oxygen and pH concentration cells are provided in the pipe
trench, and stray current sources are, or may be, installed, the only remaining major uncontrolled
corrosivity parameter is soil electrical resistivity, which is a measure of the conductivity of the
soil.
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Corrosion Considerations for Buried Metallic Water Pipe

Soil resistivity is one of the most influential parameters affecting corrosion. The importance
of soil resistivity to corrosion activity has long been recognized by corrosion engineers.
Pseudogalvanic and stray current exposures provide the driving force (voltage difference) for the
corrosion reaction. The resistance of the chemical portion of the circuit (i.e. the soil) including
the ionic resistance of the electrolyte and the metal/electrolyte contact resistances at both the
anode and cathode surfaces controls the magnitude of current flow. These resistances are
directly related to the resistivity of the electrolyte. Soil resistivity is a measure of the soil’s
moisture content and dissolved salts.
The corrosion experienced on buried metallic pipelines is more dependent on the environmental
characteristics than the compositional variations (amount and types of metal) within a specific
type of pipe. It is widely accepted that both steel and ductile iron corrode at similar rates in
similar soils (FHWA, 2001; Fitzgerald, 1968; Romanoff, 1968).
Although they corrode at approximately the same nominal rate, there is a very important
difference between the corrosion characteristics of steel versus ductile iron. Ductile iron pipe
typically corrodes by graphitization, pitting corrosion, or microbiologically influenced corrosion
(MIC). Graphitization does not occur with steel, which typically corrodes by pitting. Graphitic
corrosion is a type of dealloying in which the iron within the iron/carbon matrix of ductile iron is
preferentially corroded due to the galvanic couple between the iron and graphite. Iron is anodic
to graphite and when galvanically coupled with graphite the iron will experience accelerated
corrosion. As the iron corrodes, the iron/carbon matrix transforms to a porous iron oxide/carbon
matrix with an accompanying reduction of mechanical properties (e.g. ductility and tensile
strength). The graphitized material tightly adheres to the metal substrate. There is generally no
visible evidence of graphitic corrosion; the original pipe surface remains the same including
contour, texture, and color (there may be a very slight color change). Pitting corrosion is usually
easily identified and is visually evident by surface cavities and/or color variation due to the
presence of corrosion by-products. In either case, graphitization or pitting, the end result is the
same; a cavity will develop in the pipe wall.
Because of the tightly adhering nature of graphitic corrosion products, graphitized pipe is
capable of containing significant pressure even when corrosion has fully penetrated the pipe wall
(Romanoff, 1957; Smith, 1963). Although this is a desirable property, it cannot be relied upon as
an engineering property. The brittle nature of graphitic corrosion products result in the
graphitized pipe being susceptible to failures from stress caused by such factors as surges,
freeze/thaw, expansive soils, temperature changes, and vehicular loading. Reclamation is not
aware of any graphitization failures on any ductile iron pipe designed by Reclamation.
Microbiologically influenced corrosion occurs due to the presence and activity of bacteria in
anaerobic conditions. This type of corrosion generally occurs under disbonded coatings at pipe
surface locations that are blocked from adequate cathodic protection current, and could be a
concern under PE encasement, especially in high sulfate soils. Reclamation is not aware of any
MIC failures on any Reclamation-designed projects.

9

Corrosion Considerations for Buried Metallic Water Pipe

In summary, both steel and ductile iron pipes are vulnerable to corrosion when buried. They
corrode at approximately the same rate when exposed to the same conditions, and the corrosion
experienced is highly dependent on the corrosion characteristics of the soil and/or stray
currents.

3.3 Corrosive Soil Determination
The corrosion of metal pipe buried in soil is an electrochemical process. The more easily
electricity is conducted in the soil, the more corrosive the soil will be. Stated conversely, soils
with high resistivity are less corrosive. Therefore, the potential of soils to provide a ready path
for corrosion can be determined by field measurements to evaluate the soil resistivities.
However, field measurements will only give an indication of corrosion characteristics for in situ
soil conditions at the time the readings were taken. The worst case for determining the corrosion
characteristics of any soil would involve a laboratory test with the soil sample saturated.
Therefore, when using field measurements to determine the minimum corrosion requirements for
a pipeline, one should understand that these readings may not be the absolute worst corrosion
conditions for a given soil, but they are representative of in situ conditions. Also, low
resistivities can be an indication of high chloride or sulfate concentrations. The relative
corrosion rate at differing soil resistivities has been studied over the years by many organizations
and many criteria have been developed to portray the amount of corrosion that can be expected
to occur over the life of a project based on soil resistivity. Examples of the different evaluations
of the relationship between soil resistivity and corrosivity are shown in table 3. Reclamation has
chosen to use the in situ field measurements because we believe these readings more accurately
reflect the conditions the pipeline will encounter.
One of the correlations that can be made from the criteria in table 3 is that soils with resistivities
less than 1,000 ohm-cm are classified as very corrosive conditions and that most users classify
soil resistivities less than 2,000 ohm-cm as severe corrosion conditions. The fact that some
organizations believe 3,000 ohm-cm or less indicate corrosive conditions illustrates there is
still debate in the industry as to what soil conditions constitute a severely corrosive
environment.
In the 1970s, Reclamation developed the idea of using the soil resistivity with a 10 percent
probability of occurring along the pipeline alignment as the design resistivity. This prevents a
few erroneous test results from requiring an entire pipeline to meet more stringent corrosion
requirements and also assumes that in a worst-case scenario, only 10 percent of the pipeline
would be subject to a higher corrosion rate than expected.
The Ductile-Iron Pipe Research Association’s (DIPRA) original 10 point system (circa 1970s) is
an example of how some criteria for corrosion rates have been developed to take into account
other environmental factors in addition to soil resistivity. The 10 point system also evaluates pH,
reduced oxygen (redox) potential (aerobic or anaerobic), sulfides and moisture content. Each

10

Corrosion Considerations for Buried Metallic Water Pipe

Table 3.—Corrosivity Related to Soil Resistivity
Source

Soil Resistivity Range
(ohm-cm)

Corrosivity

NACE Publication 10A292
Technical Committee Report,
NACE Task Group T-10A-21

Below 500
500-1,000
1,000-2,000
2,000-10,000
Above 10,000

Very corrosive
Corrosive
Moderately corrosive
Mildly corrosive
Progressively less corrosive

RUSTNOT1
(Consultant)

0-1,000
1,000-3,000
3,000-5,000
5,000-10,000
Over 10,000

Extremely Corrosive
Very Corrosive
Corrosive
Moderately Corrosive
Mildly Corrosive

Bureau of Reclamation
(Paint Manual)

0-1,000
1,000-5,000
5,000-10,000
Over 10,000

Very Corrosive
Moderately Corrosive
Mildly Corrosive
Slightly Corrosive

American Water Works Association
(AWWA) AWWA - M11
Steel Pipe Manual

0-2,000
2,000-4,500
4,500-6,000
6,000-10,000

Bad
Fair
Good
Excellent

Department of Defense (DOD)
Unified Facilities Criteria
(UFC 3-570-06)
(Army, Navy, Air Force)

0-10,000
Over 10,000

Corrosive
Less Corrosive

1

Spickelmire, B., July 2002. “Corrosion Considerations for Ductile Iron Pipe,” Materials Performance,
pp. 16 – 23.

11

Corrosion Considerations for Buried Metallic Water Pipe

factor is given a numerical rating and if the total adds up to 10 or greater, some form of corrosion
protection is required. The AWWA has adopted the DIPRA 10 point system, and the AWWA
C105 table outlining the 10 point system is shown in table 4.

Table 4.—AWWA C105 Appendix A
Soil Test Evaluation
Source

Soil Characteristics

Points1

0-700
700-1,000
1,000-1,200
1,200-1,500
1,500-2,000
Over 2,000

10
8
5
2
1
0

0-2
2-4
4-6.5
6.5-7.5
7.5-8.5
Over 8.5

5
3
0
02
0
3

Over +100mV
+50 to +100 mV
0 to +50 mV
Negative

0
3.5
4
5

Positive
Trace
Negative

3.5
2
0

Resistivity – ohm-cm (based
on a single probe at pipe
depth or water saturated soil
box)

pH

Redox potential

Sulfides

Moisture

Poor drainage, continuously wet
Fair drainage, generally moist
Good drainage, generally dry

2
1
0

1

Ten points means that the soil is corrosive to gray or ductile iron pipe; protection is required.
If sulfides are present and low or negative redox potential results are obtained, three points
shall be given for this range.
2

The theory behind the DIPRA 10 point system is that even if the soil resistivities are relatively
low, there will be no corrosion if the soil properties are not corrosive to metal, although soils
with resistivities less than 700 ohm-cm would automatically require corrosion protection. The
moisture conditions around the pipe should also be considered. If the soil stays dry all of the

12

Corrosion Considerations for Buried Metallic Water Pipe

time, there will be no pipe corrosion. However, any pipeline can leak, and soil moisture
conditions can change over time. So the assumption of a dry soil condition around the pipe is
usually not valid.
The DIPRA 10 point system was developed in the early 1970s. Since that time, expanded tables
have been developed to cover even more soil properties (e.g., chlorides) as well as stray current
potential, service life, type of system (transmission or distribution), pipe size, and hydraulic
transient pressures. While all of these factors are important in the development of a pipeline
corrosion strategy, these tests can be cost intensive for long pipe alignments and very much
subject to judgment or interpretation as to which point values should be assigned. Also,
collecting and testing individual soil samples along a long pipeline alignment will likely miss
some of the soils that have corrosive characteristics. For these reasons it seems logical to use
soil resistivities as the basis for corrosion design of a pipeline. These surveys cover the entire
alignment and provide specific information as to the potential for corrosion.
After reviewing the above assessments of soil corrosivity, Reclamation has concluded that even
in the absence of other corrosion factors, any pipeline installed in environments with soil
resistivities less than 2,000 ohm-cm should be protected with the most comprehensive corrosion
protection system available for each pipe option. Reclamation has also concluded that other
corrosion factors (e.g. stray currents, soil pH, soil or groundwater chlorides or sulfides, and
redox potential) warrant consideration in designing the corrosion protection system for all
pipelines, including those installed in less corrosive soils (e.g. soil resistivities greater than
3,000 ohm-cm).

3.4 Typical Corrosion Mitigation Methods
3.4.1 Bare Pipes
Buried metallic pipelines have the potential to corrode and typically require corrosion protection.
Without a protective coating the remaining corrosion protection alternative is CP. A bare pipe
can be adequately protected with a CP system; however, the amount of current required to
protect a bare pipeline is significantly greater than the amount of current required to protect a
well-coated pipeline. The larger current requirement results in a larger number of CP ground
beds (locations at which the protective current is injected into the ground) which increases the
design, installation, operation and maintenance, and power requirement costs associated with
the CP system. Bare pipes may provide the lowest initial capital costs, but could also have the
highest maintenance costs. Keeping the CP system functioning properly for bare pipes is
absolutely essential due to the lack of protective coating.
Because of the inherent potential for metal pipes to corrode, Reclamation practice is to use some
form of encasement or bonded coating, as well as corrosion monitoring, on all metallic pipe,
even in high resistivity soils.

13

Corrosion Considerations for Buried Metallic Water Pipe

3.4.2 Polyethylene Encasement
Polyethylene encasement is a dielectric coating which is not bonded to the underlying metallic
surface. Because this type of coating is not bonded to the exterior surface of the pipe, it is
considered to be an encasement rather than a true coating. Any damaged area or discontinuity in
a coating or encasement that exposes the underlying metallic surface to the corrosive
environment is called a holiday.
Polyethylene encasement provides better protection than bare pipe, and is relatively inexpensive
when compared to bonded dielectric coatings.
No PE encasement will be holiday free. Holidays within the PE encasement can occur during
manufacturing, installation, and/or deterioration with time. At holidays, the pipe wall is exposed
to the soil, and in the presence of moisture, corrosion will occur as governed by the corrosion
characteristics of the soil. As the number of holidays increases, a correspondingly larger amount
of current is required for CP.
Cathodic protection on PE encased ductile iron pipe is a controversial issue. The concern is that
CP will not be able to protect, and monitoring will not be able to detect, areas of corrosion away
from the holidays.
The Department of Transportation does not allow PE encasement on petroleum pipelines, and
has required bonded dielectric coatings since 1970 for all soil resistivities2. Opinions on the use
and effectiveness of PE encasement within the water industry vary.

3.4.3 Bonded Dielectric Coatings
A bonded dielectric coating tightly adheres to the surface on which it is applied. Common
bonded dielectric coatings are epoxies, tape wraps, and polyurethanes. Bonded dielectric
coatings can be and have been successfully applied to both steel and ductile iron pipe (Szeliga
et al., 1993; Garrity et al., 1989; Pimentel, 2001; Brander, 2001; Lieu and Szeliga, 2002; Fogata,
2003). AWWA M41 – Ductile Iron Pipe and Fittings (1996, revised 2003), lists bonded
dielectric coatings as an alternative corrosion mitigation method for ductile iron pipe. Coatings
similar to those applied to steel pipe can be applied to ductile iron pipe; however, surface
preparation guidelines for steel pipe generally cannot be used for ductile iron pipe. In 2000 the
National Association of Pipe Fabricators, Inc (NAPF) published a standard for surface
preparation for ductile iron pipe and fittings (NAPF 500-03, 2000). Prior to the NAPF standard
there were no national standards for the surface preparation of ductile iron pipe and most
organizations had to write their own surface preparation and coating specifications. Installed

2

49 CFR Part 192.1.

14

Corrosion Considerations for Buried Metallic Water Pipe

bonded dielectric coatings are not holiday-free; however the number of holidays is usually
limited when compared to PE encasement, and will result in lower power costs than PE
encasement if CP is required. Bonded dielectric coatings are relatively expensive, but most
corrosion engineers believe they provide better corrosion protection than other coatings.

3.4.4 Cement Mortar Coatings
Cement mortar prevents corrosion by providing a passivated environment for the underlying
metal. The cement mortar is not always bonded completely with the metal or the coating can
crack or experience damage during handling, installing, or backfilling, which may lead to
corrosion. However, the use of a coal tar epoxy seal coat on the outside of the mortar creates a
coating bonded to the mortar and substantially reduces the number of holidays which penetrate to
the underlying metal, thus decreasing the power required for a CP system.

3.4.5 Corrosion Monitoring Systems
Irrespective of the amount of environmental testing that is conducted prior to pipeline design,
there is always a potential for a buried pipeline to have corrosion-related problems. If a
corrosion-related problem is identified, the corrosion monitoring system allows a means to
investigate and address the problem. Without a corrosion monitoring system the options
available to identify, investigate, and address corrosion-related problems are limited.
A corrosion monitoring system requires the pipeline to be electrically continuous. Providing this
positive electrical continuity on a pipeline will increase the probability of corrosion resulting
from stray currents. However, the corrosion monitoring system can be used to investigate,
identify, and mitigate long line and stray current corrosion. Reclamation believes the benefits of
a corrosion monitoring system far exceed the risks. Reclamation’s position has been and
continues to be that all buried metallic pipelines be installed with corrosion monitoring systems.

3.4.6 Cathodic Protection Systems
Cathodic protection is a proven method of mitigating corrosion and is the only corrosion control
method which can potentially halt ongoing corrosion of a buried pipeline. Cathodic protection
uses a corrosion cell to the benefit of the protected pipeline. With CP the pipeline that is to be
protected is made the cathode of the corrosion cell (corrosion does not occur at the cathode).
Because there is an operating corrosion cell there must be an anode. Therefore, an anode
material must be installed which will be sacrificed for the sake of the pipeline to be protected. It
should be noted that corrosion is not stopped, but is transferred from the pipeline that is to be
protected to sacrificial material which is installed to be consumed.

15

Corrosion Considerations for Buried Metallic Water Pipe

Since CP is a corrosion cell, current must flow. As with the corrosion cell, current flows from
the anode to the cathode within the electrolyte, and from the cathode to the anode within the
metallic path. For pipeline installations the electrolyte is the moisture in the surrounding soil.
The metallic path is along the pipeline and the joint bonding cables for the CP system. A
pipeline must be electrically continuous for the successful application of CP.
There are two types of CP systems, galvanic anode and impressed current. Both systems require
the installation of a sacrificial material as the anode. Galvanic anode CP requires the installation
of galvanic anodes. A galvanic anode is a material which is more electro-chemically active than
the pipeline to be protected. Galvanic anodes use the natural potential difference between the
anode material and the pipeline to cause current to flow. For soil applications zinc and
magnesium are typically used as the galvanic anode material. Galvanic anodes are typically
installed some distance from a pipeline and connected to the pipeline through cables.
External power is required to supply the current for an impressed current CP system. Any DC
type power supply can be used for CP, although a rectifier is typically used. A rectifier converts
AC power into DC power. Impressed current requires the installation of anodes and a power
supply; the power supply is connected between the pipeline and anodes. Because external power
provides the driving force for the CP current (which allows a higher potential to be reached) a
wide range of anode materials can be used. Some commonly used impressed current anode
materials include high silicon cast iron, graphite, mixed metal oxides, and platinum.
The CP system must be capable of supplying sufficient current to provide adequate corrosion
protection. Galvanic anode CP systems are limited in the current which they can provide and
therefore are typically used in situations with small current requirements (e.g. smaller pipelines
or pipelines with bonded dielectric coatings). Impressed current CP systems can provide a large
and variable amount of current and can be used in situations requiring small or large current
requirements (e.g. larger pipelines or poorly coated pipelines).

4.0 BURIED STEEL AND DUCTILE IRON PIPE
This section focuses on steel and ductile iron pipe, and includes information on corrosion
mitigation and prevention criteria, historical performance, expected service life, and life cycle
costs.

4.1 Corrosion Mitigation for Ductile Iron Pipe
Corrosion mitigation methods typically used for ductile iron pipe include PE encasement,
bonded dielectric coatings, and/or CP. Ductile iron pipe designs have historically added a
service allowance in the pipe design wall thickness as an added factor of safety against corrosion.
The wall thickness designs for ductile iron pipe were originally based on the designs for cast iron
pipe. Both steel and ductile iron will corrode at approximately the same rate in the same
16

Corrosion Considerations for Buried Metallic Water Pipe

environment. Since ductile iron pipe has a thicker wall than a comparable steel pipe, it will take
longer for corrosion to penetrate the wall of a ductile iron pipe than a comparable steel pipe.
This phenomenon is one reason pipeline designers have allowed ductile iron pipe to be installed
with PE encasement in locations where a comparable steel pipe required the more robust bonded
dielectric coating.3 In recent years, the ductile iron pipe industry has reduced the wall thickness
of the pipe based on the superior structural performance characteristics of ductile iron compared
to cast iron. So, while the designed service allowance for ductile iron pipe has remained the
same for many years, the overall ductile iron pipe wall thickness (when adding wall thicknesses
for structural strength and the service allowance) is thinner than the cast or ductile iron pipes
previously produced. This reduction in ductile iron pipe wall thickness has raised concerns
within the water industry over the longevity of the pipe in corrosive environments.
Ductile iron pipe has also been installed by some water utilities without coatings of any kind (see
table 5). This pipe is considered to be “bare.”
Various corrosion control method philosophies are currently used by ductile iron pipe users
within the U.S. (water utilities), DIPRA, NACE (National Association of Corrosion Engineers),
and water utilities outside the U.S. to control corrosion. A brief discussion of the various
corrosion control method philosophies are listed below:

3
4

•

U.S. Water Utilities – In some instances, water utilities are using corrosion control
methods recommended by sources such as DIPRA, NACE, other water utilities and other
countries. Other water utilities are creating or adjusting their own corrosion control
method philosophies based on historical data and experience from their installed
pipelines.

•

DIPRA – The association recommends the use of PE encasement for ductile iron based
on extensive historical performance. DIPRA points out that “since 1958, PE encasement
has been used to protect millions of feet of cast and ductile iron in thousands of
installations across the U.S.”4 Additionally, DIPRA points out that “There has been no
instance where the soil evaluation procedure has proved inadequate or faulty in predicting
where corrosion protection is needed.”4 DIPRA strongly disagrees with the recent
tendency of corrosion engineers who advocate the universal application of joint bonding
and the installation of test leads on all pipe systems regardless of soil corrosivity or
potential for stray current corrosion. DIPRA asserts that CP is very expensive to install
compared to PE encasement. DIPRA asserts that CP can be applied to ductile iron pipe
and can be successful under certain circumstances, but is seldom cost effective. In most
cases, DIPRA asserts that CP is also unnecessary due to the availability of alternative
methods of corrosion control that are equally reliable and less expensive. Additionally,
the American Water Works Association (AWWA) has adopted the DIPRA 10 point
system for soil assessment for ductile iron pipe in AWWA’s C105 publication. In
August of 2002 DIPRA announced that the eight leading manufacturers in North America

49 CFR Part 192.1.
Stroud, T.F., 1988. “Polyethylene Encasement versus Cathodic Protection: A View on Corrosion Protection.”

17

Corrosion Considerations for Buried Metallic Water Pipe

will no longer honor a warranty for ductile iron pipe with any exterior dielectric coating
other than polyethylene encasement.5 In cooperation with DIPRA, Corrpro Companies
Inc., prepared a document in 2004, which proposes an updated “Design Decision Model”
for corrosion protection of ductile iron pipe. Their report concludes that “Bonded,
dielectric coatings are not a cost-effective solution for corrosion protection of ductile
iron pipe. . .”.6
•

NACE – The National Association of Corrosion Engineers (NACE) corrosion control
method recommends the use of bonded dielectric coating and, if required, CP for all
metallic pipe systems. Individual pipes are joint bonded for electrical continuity to
facilitate corrosion monitoring via pipe to soil measurements of electrical potential and, if
required, CP. NACE has expressed concern about the performance of polyethylene wrap
on ductile iron pipe. For example, NACE International’s RP0169-2002 “Control of
External Corrosion on Underground or Submerged Metallic Piping Systems,” requires a
bonded dielectric coating for buried pipeline applications and expresses concern that
unbonded coatings (PE is considered an unbonded coating) can create electrical shielding
of the pipeline that could jeopardize the effectiveness of the CP system.

•

Water Utilities Outside the U.S. – Some countries (European and Japan) employ a
combination of coating systems and, if required, CP, for ductile iron pipe. The coating
systems can involve a combination of PE wrap, coal tar enamel for outside protection,
and zinc coatings. In a corrosive environment, these utilities recommend that both a
bonded dielectric coating and CP be used.

4.1.1 Effectiveness of Polyethylene Encasement on Ductile Iron Pipe
Polyethylene encasement was first used on a buried pipeline in the early 1960s. The use of PE
encasement within the water industry is controversial. The major controversies related to ductile
iron pipe involve the effectiveness of PE encasement as a corrosion mitigation method and the
compatibility of PE encasement and CP. It is widely accepted that corrosion on the pipe wall
opposite from PE encasement holidays can be mitigated by CP. The technical disagreements
generally are focused on the occurrence of corrosion under intact PE encasement and the
mitigation of that corrosion by the use of CP.
Below are the more prominent issues that are generally presented by the proponents and
opponents of PE encasement.
Proponents of the use of PE encasement indicate that in most corrosive soils, PE encasement
alone is the recommended corrosion mitigation technique (AWWA M41, 2003; Kroon et al.,
5

Infrastructure Preservation News, Vol. 1, No. 2, June 2003. “Assessing DIPRA’s New Corrosion Protection
Standards.”
6
Kroon, David H., Dale Lindemuth, Sheri Sampson, and Terry Vincenzo, Corrpro Companies Inc., 2004. NACE
International, Paper No. 04046, “Corrosion Protection of Ductile Iron Pipe.”

18

Corrosion Considerations for Buried Metallic Water Pipe

2004). However, in uniquely severe environments other corrosion mitigation techniques, such as
bonded dielectric coating and/or CP, should be considered (Stroud, 1989). This also includes the
use of CP with polyethylene encased ductile iron pipe, where the PE encasement reduces the
amount of CP current required (Smith, 1970; Clark, 1972; Stroud, 1989; Lisk, 1997). American
Water Works Association (AWWA) C105 “Polyethylene Encasement For Ductile-Iron Pipe
Systems” is a national standard which is often referenced as supporting documentation for PE.
AWWA C105 covers materials and installation procedures for PE encasement on ductile iron
pipe. A non-mandatory appendix in AWWA C105 covers how to determine if corrosive soils are
present.
Proponents of the use of PE encasement generally agree with the following:
1.

The mechanism of corrosion protection provided by PE encasement is that of placing
a dielectric barrier between the pipe wall and soil that causes oxygen starvation
within the corrosion cell.

2.

Intact PE encasement prevents direct contact between the pipe and soil.

3.

The PE encasement is not bonded to the pipe surface and can therefore allow
moisture within the annular space between the pipe and PE. The moisture, when
present, and its dissolved oxygen will initially result in corrosion on the pipe surface,
but once the dissolved oxygen is consumed by the initial corrosion reaction, further
corrosion activity will be stifled. The moisture within the annular space, after being
devoid of dissolved oxygen, then provides a non corrosive, uniform environment to
the pipe surface.

4.

The PE encasement retards the transport of dissolved oxygen to and corrosion
products away from the pipe surface.

5.

Significant exchange of moisture within the annulus is prevented by the weight and
compaction of the backfill, which presses the PE encasement against the pipe.

6.

Stray current corrosion from external sources is reduced by the dielectric barrier of
the PE encasement.

7.

Although CP may not be required, polyethylene encased pipe can be successfully
cathodically protected.

DIPRA has an inspection program under which they have conducted a number of inspections on
operating pipelines with PE encasement. The inspection program indicates that ductile iron pipe
is protected with the use of PE encasement (Stroud, 1989). Others have reported that corrosion
under undamaged PE encasement is very low (Schiff and McCollom, 1993). A continuation of
Schiff and McCollom work indicates that corrosion under undamaged PE encasement has
remained low, that the corrosion rate under undamaged polyethylene is an order of magnitude
less than that experienced outside the polyethylene within sand backfill, and that CP is effective
under undamaged polyethylene (Bell, 2003).
19

Corrosion Considerations for Buried Metallic Water Pipe

Opponents to the use of PE encasement indicate that the pipe surface opposite holidays in the
PE encasement experiences corrosion, pipe surfaces under intact PE encasement experience
corrosion between the holidays in the PE encasement, and corrosion occurring under these areas
cannot be mitigated by CP (Fitzgerald, 1968; Garrity et. al., 1989; Noonan, 1996; Szeliga and
Simpson, 2001; Spickelmire, 2002). The opponents further indicate that corrosion under areas
of intact PE encasement cannot be detected by above- ground corrosion monitoring methods
(e.g., pipe-to-soil potential surveys) and corrosion under intact polyethylene will go undetected
until failure (Szeliga and Simpson, 2003).
Opponents to the use of PE encasement often reference the following three national documents
as supporting documentation of their position:
•

The NACE International’s Recommended Practice RP0169-2002 “Control of External
Corrosion on Underground or Submerged Metallic Piping Systems.”

•

The Code of Federal Regulations (CFR) Title 49 parts 192 and 195 (October 1, 2002) as
enforced by the U. S. Department of Transportation’s Office of Pipeline Safety.

•

The Docket No. OPS-5A (Federal Register Vol. 36, No. 166 – Thursday, August 26,
1971).

Although the three documents noted above were primarily developed for the oil and gas industry,
the information contained in them is relevant to this discussion. In fact, RP0169-2002 includes
water systems in its recommendations.
The NACE Document RP0169 requires a bonded dielectric coating for buried pipeline
applications and indicates that unbonded coatings such as PE encasement can create electrical
shielding of the pipeline that could jeopardize the effectiveness of the CP system.
49 CFR 192 and 195 do not allow unbonded coatings as an acceptable corrosion mitigation
technique for federally regulated pipelines. Federally regulated pipelines include pipelines
which transport natural gas or hazardous liquids (water pipelines are not federally
regulated).
In Docket No. OPS-5A, the Office of Pipeline Safety specifically denied a petition to permit the
use of PE encasement for cast and ductile iron pipes as an alternative method of corrosion
control, and as indicated by 49 CFR 192 and 195, this is the Office of Pipeline Safety’s current
position.
Pipe corrosion under areas of intact PE encasement has been reported (Szeliga and Simpson,
2003; Spicklemire, 2002; Fogata, 2003). The ductile and cast iron pipelines inspected in
San Diego during the CIPRA 1968 and DIPRA 1981 excavations have experienced corrosionrelated failures (Fogata, 2003). The San Diego cast iron pipeline was one of the initial

20

Corrosion Considerations for Buried Metallic Water Pipe

installations of PE, installed in 1961, and the soil in which the pipelines were buried is
considered very corrosive (DIPRA, 1981). Corrosion and the mitigation of corrosion under
disbonded coatings has been a concern within the corrosion industry for a number of years.
In summary, proponents of and opponents to the use of PE encasement agree that corrosion can
occur at locations where holidays in the PE encasement expose the pipe wall to the soil and that
the resulting corrosion can be mitigated by CP. Proponents and opponents agree that corrosion
can take place under areas of intact PE encasement between holidays; however, they do not agree
on the severity of corrosion that can take place. The proponents indicate that under most
situations the corrosion reaction occurring under intact PE encasement will be reduced over time
and significant corrosion does not occur. The opponents argue that 100 percent intact PE
encasement is not feasible, that the corrosion reaction under intact PE encasement is not reduced
over time, that significant corrosion can occur, and that CP can not be used to mitigate the
corrosion.
Backfill aggregate size and type can be very important in determining the effectiveness of PE
encasement with regard to reducing corrosion and CP costs. The use of large diameter angular
gravel as backfill can lead to perforations in the PE encasement and should be avoided. See
appendix F.
Both successful and unsuccessful applications of PE encasement on ductile pipe without CP
have been reported, although most installations with both PE encasement and CP seem to
be performing satisfactorily. It should be noted, however, that the nature of the corrosion
experienced on cast and ductile iron pipe is such that the recognition of corrosion related failures
is not readily apparent, creating the possibility that corrosion failures may not be fully accounted
for. After 40 years of use, there are still basic issues regarding the use of PE encasement for
corrosion protection of ductile iron pipe that are unresolved.

4.1.2 Peer Review of Reclamation’s Evaluation of PE Encasement
for Ductile Iron Pipe
A Review Panel was convened by Reclamation in March of 2004 to peer review Reclamation’s
evaluation of the effectiveness of unbonded coatings on metallic pipe. The Panel consisted of
two private sector corrosion engineers (G.E.C. Bell, M.J. Schiff & Associates, Claremont, CA;
and R.Z. Jackson, CH2M Hill, Sacramento, CA) and a materials scientist from the National
Institute of Standards and Technology (NIST). (Y. Cheng, Materials Reliability Division,
Boulder, CO). Also included by contract was an independent Panel chair and technical assistant
to serve as a referee to incorporate the panelists’ comments into a peer-reviewed document
(NIST: (C.N. McCowan (Panel Chair) – Boulder; and R.E. Ricker, Metallurgy Division,
Gaithersburg, MD)).
The panel peer reviewed a February 2004 draft of an evaluation of corrosion mitigation issues
related to ductile iron pipe prepared by Tom Johnson (Reclamation’s corrosion engineer until
21

Corrosion Considerations for Buried Metallic Water Pipe

leaving for a position with another agency in February of 2004). A copy of this evaluation which
has been updated to include the panel’s comments is included in appendix B. The peer review
comments were considered and incorporated into Section 8 (Recommendations). The panel was
also asked to respond to a series of six questions regarding corrosion protection practices. The
six questions and the panel’s conclusions are included in appendix D. Reclamation’s responses
to the panel’s input are included in appendix A.

4.2 Corrosion Mitigation for Steel Pipe
Corrosion mitigation measures typically used for steel pipe differ from those used on ductile iron
pipe in recognition of the differing material properties of the two materials. The different
material properties of steel allow steel pipes to be designed with much thinner walls than
comparable ductile iron pipes. When a service allowance is added to the ductile iron pipe wall
thickness (which has not historically been added to the steel pipe wall thickness), the difference
in wall thicknesses between the two pipe options becomes even larger. Because both steel and
ductile iron corrode at similar rates in similar soil conditions, corrosion will penetrate the thinner
walls of a steel pipe more quickly than the thicker wall of a ductile iron pipe. This has led
Reclamation and other water utilities, as well as corrosion consultants, to adopt more aggressive
corrosion protection measures for steel pipe.
Steel pipes have been installed with dielectric coatings such as, epoxies, tapes, and polyurethane.
Bonded dielectric coatings adhere to the metallic pipe surface and have a high resistance to
electric current flow.
Cement mortar has also been used as a coating for corrosion protection on steel pipe. According
to AWWA C205 (Cement mortar Protective Lining and Coating for Steel Water Pipe - 4 in. and
Larger - Shop Applied), “bond or adhesion” exists between the cement mortar coating and the
steel cylinder.
For the purposes of corrosion protection, the cement mortar coating provides a reservoir of
alkalinity, thus passivating the steel provided intimate contact exists between the mortar and the
steel. Without a coal tar epoxy seal coat, the cement mortar coating is porous, thereby allowing
the ingress of moisture and dissolved salts during wetting and drying cycles. If the cement
mortar coating does not have a coal tar epoxy seal coat, it is considered to be no more or no less
effective than PE encasement on ductile iron pipe in reducing corrosion.
Cathodic protection has been applied to steel pipe in corrosive environments with bonded
dielectric or mortar coatings. Standards for cement mortar coatings and bonded coatings on
steel pipe are covered by AWWA. To the best of Reclamation’s knowledge, the use of PE
encasement as a corrosion protection system over bare steel pipe is not recommended by any
national standard. Reclamation has not used this approach for corrosion protection of its
buried steel pipe, and none of the water utilities surveyed indicate that they have used this
method.
22

Corrosion Considerations for Buried Metallic Water Pipe

4.3 Corrosion Prevention Criteria
4.3.1 Previous Reclamation Guidelines
The corrosion criteria and requirements updated on April 23, 2003 are shown in table 1. Table 1
contains recommended corrosion mitigation measures for various pipe alternatives and various
soil conditions. The table’s recommended methods of protection include some measure of
protection for all metallic pipe and more aggressive protection measures for more corrosive
environments.
Within Reclamation, the type of coating and CP requirements for buried pipelines are based on
the material properties of the pipe and soil resistivity. The corrosion prevention criteria and
requirements are guidelines used by Reclamation when making corrosion prevention
recommendations for buried pipeline alternatives. The design recommendations in the table are
based only on the 10-percent probability value of soil resistivity. It should be noted that other
parameters such as performance history and stray current exposure for a given route, criticality
of the pipeline, conservatism employed in the design, and specific client requests should be
considered when determining corrosion prevention requirements for a specific pipeline.
Reclamation’s standard practice was to use the criteria and requirements to determine the
appropriate methods of corrosion protection of buried pipelines designed by Reclamation which
remain in Federal ownership. The criteria and requirements were not intended to be a rigid
requirement, but rather a tool used in formulating the corrosion protection scheme on a particular
pipeline. The specified corrosion prevention requirements for a particular pipeline should be
developed by a corrosion engineer working directly with the pipeline designer.
For ductile iron pipe, the table includes options to use PE encasement or bonded dielectric
coating. In more corrosive soils, a CP system was recommended to supplement the protection
provided by the protective encasement or coating. A footnote was added to the table in the early
1990s which added a recommendation to limit the use of PE encasement to ductile iron pipe
24 inches in diameter or smaller (and 150 lb/ft or lighter). This provision was based on a
concern about potential damage to the encasement during installation of larger and heavier
pipe.
For steel pipe, the table includes options to use bonded dielectric coating, mortar coating with
coal-tar epoxy, or mortar coating alone. As with ductile iron pipe, a CP system was
recommended in more corrosive soils to supplement the protection provided by the protective
coating.

4.3.2 National Industry Standards
Widely recognized water and corrosion industry standards, such as NACE, AWWA,
and the Department of Transportation, are similar in their corrosion prevention
23

Corrosion Considerations for Buried Metallic Water Pipe

recommendations for steel pipe. However, the standards differ widely in the recommended
practice for corrosion prevention of ductile iron pipe, mainly with regard to the use of PE.
American Water Works Association (AWWA):
•

AWWA M41, “Manual of Water Supply Practices, Ductile-Iron Pipe and Fittings,” was
issued in 1996 and revised in 2003 and recommends PE encasement for corrosion
protection of ductile iron pipe, but acknowledges that alternate methods such as bonded
dielectric coatings, among others, may be appropriate in certain circumstances. The
standard discusses the use of CP as an economic alternative for corrosion protection. No
limitations are placed on the use of PE encasement based on pipe diameter.

•

AWWA C105, “Polyethylene Encasement for Ductile-Iron Pipe Systems,” was first
issued in 1972 and the most current version was issued in 1999. The standard covers
materials and installation procedures for PE encasement for ductile iron pipe. A nonmandatory appendix to the standard outlines a 10 point system to be used to determine
the need for corrosion protection. The standard does not identify a restriction for the use
of PE encasement relative to pipe diameter. The standard states that cuts, tears,
punctures, or other damage to the PE encasement shall be repaired, and that care should
be taken to prevent damage to the PE encasement when placing backfill.

•

AWWA M11, “Manual of Water Supply Practices, Steel Pipe – A Guide for Design and
Installation,” was first issued in 1964 with the current version issued in 2004. The
chapter on coatings and linings recommends bonded dielectric coatings or cement mortar
coating for steel pipe. The manual states that the addition of a corrosion allowance to the
steel pipe wall thickness is not an “. . .applicable solution. . .where standards for coating
and lining materials and procedures exist.” The manual suggests that cathodic protection
is widely used by water utilities for corrosion control, and that a coating with high
adhesion is required.

National Association of Corrosion Engineers (NACE):
•

NACE Publication 10A292 Technical Committee Report, NACE Task Group T-10A-21,
“Corrosion Control of Ductile and Cast Iron Pipe”, 1992. This publication states that
“…polyethylene sleeves are protective when undamaged, as are other coatings when
undamaged”, and does not mention any limitation on the use of PE encasement based on
pipe diameter. It also states that “joint bonding is necessary for electrical continuity if CP
is considered.”

•

RP0169 “Control of External Corrosion on Underground or Submerged Metallic Piping
Systems” manual is a recommended practice first issued in 1969 with the most current
revision issued in 2002. This manual states that “Pipeline external coating systems shall

24

Corrosion Considerations for Buried Metallic Water Pipe

be properly selected and applied to ensure that adequate bonding is obtained. Unbonded
coatings can create electrical shielding of the pipeline that could jeopardize the
effectiveness of the cathodic protection system.”
American Society for Testing and Materials (ASTM):
•

A674-00 “Standard Practice for Polyethylene Encasement for Ductile Iron Pipe for Water
and Other Liquids.” This document has an appendix similar to AWWA C105 discussing
the 10 point system. The standard does not identify a restriction for PE encasement
relative to pipe diameter. The standard states that any rips, punctures, or other damage to
the PE encasement should be repaired with adhesive tape or with a short length of PE
tubing cut open, wrapped around the pipe, and secured in place. The standard also states
that special care should be taken to prevent damage to the PE wrapping when placing
backfill.

4.3.3 Water Utilities Criteria
Reclamation conducted an informal survey of several water utilities to determine the criteria they
use for corrosion protection of their steel and ductile iron pipelines. Approximately 10 water
utilities across the United States were interviewed including the City of Aurora (Colorado),
City of Houston (Texas), City of San Diego (California), Denver Water (Colorado), East Bay
Municipal Utility District (Oakland, California), Huntsville Utilities Water Department
(Alabama), Los Angles Department of Water and Power (California), Newport News
Waterworks (Virginia), Seattle Public Utilities (Washington), and Washington Suburban
Sanitary Commission (Maryland). Of major interest was the relationship of soil resistivities or
other criteria for pipe corrosion protection measures such as PE encasement, tight bonded
coating systems including dielectric coatings, and/or cathodic protection. If available, the water
utilities’ corrosion criteria for steel and ductile iron pipe was requested during the survey. In
some instances, the water utilities employed general procedures rather than specific corrosion
guidelines. For example, some water utilities based their corrosion criteria on the purpose
of the pipeline, such as whether the pipeline is used for transmission or distribution of
water.
According to some water utilities’ philosophies, transmission pipelines are more critical than
distribution pipelines. Generally, a transmission pipeline provides water to one or more
distribution pipelines and typically serves a greater number of water users. The distinction
between transmission and distribution pipelines was characteristically based on pipe diameter
and the number of water users serviced. Distribution pipelines were smaller pipe diameters,
usually less than 24 inches, which served a limited number of water users. According to some
water utilities, transmission pipelines required greater consideration and study with respect to
corrosion during the design phase given the number of water users serviced.

25

Corrosion Considerations for Buried Metallic Water Pipe

Additionally, the Department of Defense Unified Facilities Criteria (UFC 3-570-06) dated
January 31, 2003 are used jointly by the Departments of the Army, Navy and Air Force. The
Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning,
design, construction, sustainment, restoration and modernization criteria. The UFC applies to the
Military Departments, the Defense Agencies and the Department of Defense Field Activities.
U.S. Army Corps of Engineers (USACE), Naval Facilities Engineering Command (NAVFAC)
and Air Force Civil Engineer Support Agency (AFCESA) are responsible for administration of
the UFC system.
A summary of the survey results is shown in table 5.

4.3.3.1 Survey Results
The survey results indicated varying philosophies for corrosion protection of ductile iron
pipelines by water utilities. The corrosion protection philosophies were based on individual
historical experience, DIPRA and NACE philosophies or a combination of all three.

4.3.3.2 Ductile Iron Pipe Survey Results
A true consensus was not evident with respect to ductile iron corrosion protection measures for
the various water utilities surveyed. Water utilities’ ductile iron pipeline corrosion protection
criteria included the following range of positions:
•

Use of DIPRA’s / AWWA’s 10 point system for evaluation of corrosion, including the
use of PE encasement if required.

•

Use of DIPRA’s / AWWA’s 10 point system with restrictions. For example, the use of
DIPRA’s / AWWA’s 10 point system for distribution pipelines only, and the use of a
NACE philosophy (tight bonded coating system and/or cathodic protection) for
transmission pipelines.

•

Use of a NACE philosophy (tight bonded coating system and/or cathodic protection)
for the evaluation of corrosion for all pipelines. The use of PE encasement is not
recommended.

•

Development and use of a corrosion protection measure based on a combination of
individual historical experience, pipeline purpose (transmission or distribution pipeline),
and DIPRA and NACE philosophies.

26

Table 5.—Survey Summary of Water Utilities
Polyethylene
Encasement (PE) –
Ductile Iron
No discussion on PE
encasement

Tight Bonded Coating –
Ductile Iron
Yes, NACE RP0169 is cited

Cathodic Protection (CP) –
Ductile Iron
Yes for soils < 10,000 ohmcm; NACE RP0169 is cited;
When soil resistivities are
above 10,000 ohm-cm
bonded joints only

Corrosion Criteria – Steel
Corrosion control by coating
supplemented with cathodic protection or
by some other proven method. Unless
investigations indicate corrosion control is
not required

Tight Bonded
Coating – Steel
Yes, NACE
RP0169 is cited

Cathodic
Protection (CP) –
Steel
Yes

Utility
DOD – Unified
Facilities Criteria
(UFC 3-570-06)
(Army, Navy,
Air Force)

Corrosion Criteria – Ductile Iron
Yes for soils < 10,000 ohm-cm;
NACE RP0169 is cited; When
soil resistivities are above
10,000 ohm-cm bonded joints
only

City of Aurora

Uses AWWA/DIPRA 10 pt
system; Ductile iron may be
used in soils > 1,000 ohm-cm;
For soils < 1,000 ohm-cm, PVC
is used; > 10 pts uses PVC
Project-by-project corrosion
assessment; CORRPRO;
NACE approach

Yes, all ductile iron;
8 mils; Satisfied with
PE encasement

No

Yes, based on the size of the
pipe and type of soil in which
it is laid. CP for > 12" with PE

Performs actual NACE design

Three layer
tapecoat 80 mil
Polyken YG-III

Yes, impressed
current

Yes, unless CP is
provided

Yes, polyurethane 25 mils;
Bonded epoxy for fittings

Yes, unless PE is used

Project by project corrosion assessment;
CORRPRO; NACE approach

Yes, impressed
current

City of San Diego

Cathodic protection on every
pipeline.

Yes, 24 mil coal tar or wax
tape system. According to
1999 Spec - Polyurethane
25 mils; Fusion bonded epoxy
14 mils; Coal tar enamel

All lines are cathodically
protected. Impressed current
and sacrificial anodes

Cathodic protection on every pipeline

Denver Water

Soils < 1,000 ohm-cm use
plastics unless local water
district requires ductile (if below
1,000 ohm-cm require cathodic
protection on polyethylene
encased ductile iron)
None. Uses steel pipe with
tight bonded coating and
cathodic protection now

NO PE. DIPRA test
site (24-inch, installed
in 1967) has had
failures and is no longer
listed in DIPRA
literature. The PE has
deteriorated in some
places. DIPRA had no
explanation. They have
had several failures
under intact PE
encasement
Yes, standard on all DI;
Satisfied, no problems
since 1980 so far

Yes, tape coating
80 mils; Cement
mortar, polyurethane 25 mils
Tape wrap since
1990; Coal tar
enamel; Fusion
bonded epoxy;
Polyurethane
25 mils; Same for
fittings

No

Yes if below 1,000 ohm-cm;
Sacrificial anodes; Since late
1980s to early 1990s; No
corrosion problem

Tight bonded coating and CP always

Yes - always;
Polyken YG-III;
Satisfied; Fittings
Polyken YG-III and
wax tape

Yes, for ductile iron
pipelines—the pipe,
valves, fittings, and
appurtenances shall
have PE encasement.
Primarily at test site; No
followup

Would consider it if ever
specified ductile iron

Yes for one ductile iron line
(12"); Since 1980; No
problems noted

Soils < 1,000 ohm-cm highly corrosive;
Soils > 2,000 ohm-cm although
supporting corrosion are relatively slower
acting as resistivity increases

Polyethylene
encasement if in low pH
soils (< 5). Asphaltic DI
for most part

No

No

None

Yes, cement mortar
with PE
encasement
special cases
(Stray current, pH,
etc.), extruded
plastic, tape
wrapped plastic,
coal tar enamel
No tight bonded
coating on old steel
line—line is being
replaced

CP - always;
Required for
steel; Since mid
1960s; No
problems;
Limited leakage
Yes, benefit to
cost of 24 to 1 for
CP on steel
pipeline; CP on
PE encased
mortar coated
steel

City of Houston

East Bay Municipal
Utility District

Huntsville Utilities
Water Department

DIPRA Soil Testing Program;
Asphaltic coated ductile iron;
Polyethylene where necessary;
Polyethylene encasement if in
corrosive or low pH soils

27

Yes, impressed
current and
sacrificial anodes

No

Table 5.—Survey Summary of Water Utilities
Utility
Los Angles
Department of Water
and Power

Corrosion Criteria – Ductile Iron
Developed a water service map
based on corrosion test sites
and survey

Newport News
Waterworks

General procedures:
Distribution main < 16"
exclusive DI; Use 10 pt
DIPRA system. PE and
forget it (passive corrosion
protection PE encasement).
Transmission lines
> 16" NACE process is
followed and an active
corrosion protection system is
used
Old criteria were to use
corrosion protection multilayer
polyethylene tape coating for
DI in soils < 2,500 ohm-cm.
80 mils according to standard
specifications; New criteria
require thermoplastic coated
ductile iron with fusion bonded
coated fittings 25 to 30 mils;
Also uses polyurethane coating
now. As soil resistivities
increase, 8 mil PE encasement
is used in conjunction with
bonded joints and sand backfill.
Yes, own point system based
on pH, chlorides, redox
potential, soil description, soil
resistivity; if >15.5 pts., severe
corrosion

Seattle Public Utilities

Washington Suburban

Polyethylene
Encasement (PE) –
Ductile Iron
Yes, standard practice.
From a practical
standpoint, it is hard to
install PE on ductile
iron without damage

Tight Bonded
Coating – Steel
Yes, use steel with
dielectric coating
with cement mortar
rock shield and CP
for hilly and high
pressure areas.
Coal tar enamel
and extruded
polyolefin coatings

Cathodic
Protection (CP) –
Steel
Yes, standard for
steel pipe with
dielectric coating.
Also used in hilly
and high
pressure areas.
Use both
impressed and
sacrificial
anodes.
Satisfied with CP
Yes

Tight Bonded Coating –
Ductile Iron
One case of ductile iron with
dielectric coating near a
subway

Cathodic Protection (CP) –
Ductile Iron
One case of cathodic
protection

Yes, since 1972

Tight bonded coatings on
ductile iron depending on
route corrosivity; High quality
bonded dielectric coating Polyken’s 80 mil YGIII
coating. In the ground 10 to
15 yrs limited inspection;
Craftsmanship key; Weather
sensitivity an issue

Yes on large transmission
lines >36"

Stopped using steel 10 yrs ago

Epoxy

As soil resistivities
increase, 8 mil PE
encasement is used in
conjunction with
bonded joints and sand
backfill. This
combination is used as
an intermediate point
for corrosion
prevention.

New criteria require
thermoplastic coated ductile
iron with fusion bonded
coated fittings 25 to 30 mils;
Also uses polyurethane
coating now; Old criteria
required multilayer polyethylene tape coat 50 to
80 mils; Fittings coatings tape wrap and epoxy coating

Yes

Not available

Yes - tape wrap
coating; In ground
approximately
10 yrs

Yes; Some
pipelines are just
monitored; CP in
the ground
approximately
10 yrs. The
frequency of
leaks has
diminished
(becoming lower
as CP was
applied)

Yes for ductile iron
<30”; Project by project

Ductile iron >30”; Bonded
dielectric (epoxy, tape) liquid
epoxy, polyurethane

Yes, sacrificial

Tight bonded coating and CP always

Dielectric coated
steel, coal tar
enamel; Polyken
YG-III; Same for
fittings

Yes, always use
CP for steel

28

Corrosion Criteria – Steel
Tight bonded coating and CP required on
all steel pipes

Corrosion Considerations for Buried Metallic Water Pipe

Soil resistivity data is being used by some utilities to evaluate corrosion potential. Soil resistivity
limits for specific corrosion protection measures for ductile iron pipelines varied considerably
between water utilities. Examples of the criteria used are shown below:
•

If soil resistivity is below 10,000 ohm-cm, protective coatings and cathodic protection are
recommended.

•

If soil resistivity is below 2,500 ohm-cm a tight bonded coating system is recommended.
As soil resistivities increase, 8 mil PE encasement is used in conjunction with bonded
joints and sand backfill. This combination is used as an intermediate point for corrosion
prevention.

•

If soil resistivity is below 1,000 ohm-cm, the use of PVC instead of ductile iron pipe is
recommended.

•

If soil resistivity is below 1,000 ohm-cm, PE encasement and CP is recommended.

•

A tight bonded coating and CP are required for every pipeline as a standard practice
regardless of soil resistivity.

•

Every pipeline is required to have PE encasement as a standard practice.

•

Specific corrosion protection measures are performed on a project-by-project basis using
NACE philosophy.

•

Ductile iron pipe is not used, regardless of soil conditions.

Specific corrosion prevention measures for ductile iron pipelines used by the surveyed water
utilities included but were not limited to:
•

Ductile iron pipe with asphaltic coating provided by the manufacturer only.

•

Ductile iron pipe with PE encasement.

•

Ductile iron pipe with PE encasement and CP.

•

Ductile iron pipe with tight bonded coating system.

•

Ductile iron pipe with tight bonded coating system and CP.

29

Corrosion Considerations for Buried Metallic Water Pipe

4.3.3.3 Steel Pipe Survey Results
For steel pipelines a general consensus was readily apparent and was primarily based on the
NACE philosophy. The NACE philosophy is based on the use of tight bonded coating systems
and cathodic protection. For example, water utilities’ steel pipeline corrosion protection
philosophies were:
•

Use of a NACE philosophy (tight bonded coating system and/or CP) for corrosion
prevention measures.

•

Use of a cement mortar coating system and PE encasement, with CP, for corrosion
prevention measures.

Soil resistivity data is being used by some utilities to evaluate soils. Soil resistivity limits for
specific corrosion protection measures for steel pipelines varied from water utility to water
utility, as demonstrated by the example criteria shown below.
•

Corrosion control using coating supplemented with CP unless investigations indicate
corrosion control is not required.

•

Every steel pipeline is subjected to tight bonded coating and CP as a standard practice
regardless of soil resistivity.

•

Soil resistivity < 1,000 ohm-cm is considered highly corrosive. Tight bonded coating and
CP is recommended.

•

Specific corrosion protection measures are performed on a project-by-project basis using
NACE philosophy (tight bonded coating system and/or CP).

Specific corrosion prevention measures for steel pipelines used by the surveyed water utilities
included but were not limited to:
•

Steel pipe with tight bonded coating system.

•

Steel pipe with tight bonded coating system and CP.

•

Steel pipe with cement mortar coating and PE encasement, with CP.

•

No water utilities surveyed allowed PE encasement on bare steel pipe.

•

Steel pipe is not used, regardless of soil conditions.

30

Corrosion Considerations for Buried Metallic Water Pipe

4.4 Historical Performance
A technical review of available reports and data was performed on historical performance (i.e.
breaks/mile/year) of steel and ductile iron pipes. Reclamation, American Water Works
Association Research Foundation (AWWARF) and other sources were investigated for available
reports and data.

4.4.1 Summary of Reports and Data Reviewed
The following reports and data were examined:
•

Bureau of Reclamation Report Number: R-94-12 - Historical Performance of Buried
Water Pipe Lines by Kurt von Fay and Michael Peabody; September 1994.
The results of Reclamation’s report No: R-94-12 are shown in table 6. Reclamation and
AWWARF steel and ductile pipe data were examined through a formal survey. A
detailed breakdown of Reclamation and AWWARF data is also included in table 6.
Historical performance of a particular pipe type is quantified by the number of
failures/mile/year. Failures are defined as corrosion, external damage, fish mouth,
installation damage, or other or undetermined, which required some type of action after
installation to correct a pipe deficiency – namely repair, replacement or both.
Reclamation’s data for steel and ductile iron pipe were 0.0545 and 0.000 failures per mile
per year, respectively. AWWARF’s data for steel and ductile iron pipe were 0.0064 and
0.0179 failures per mile per year, respectively. The combined data for Reclamation and
AWWARF for steel and ductile iron pipe were 0.0340 and 0.0175 failures per mile per
year, respectively.

•

National Research Council of Canada – A-7019.1 Final Water Mains Breaks Data on
Different Pipe Materials for 1992 and 1993, by B. Rajani, S. McDonald, G. Felio;
1995.
The results of this report are shown in table 6. This report presents data collected on
water main breaks during 1992 and 1993 from 21 Canadian cities. The results of the
1995 National Research Council of Canada Report indicated ductile iron has an average
0.15 breaks/mile/year (9.5 breaks/100 km/year), asbestos-cement pipe average break
0.093 breaks/mile/year (5.8 breaks/100km/year) and PVC average 0.01 breaks/mile/year
(0.7 breaks/100km/year). Steel pipe was not studied in this report. The age of the water
mains and the cause of the breaks were not included in this study.

31

Corrosion Considerations for Buried Metallic Water Pipe

•

AWWARF No. 90677 – Distribution System Performance Evaluation by A. Deb, Y. Hasit,
F. Grablutz; October 1995.
The results of this report are shown in table 6. The objectives of this report were to
identify and define distribution system performance criteria and measures, develop
procedures to evaluate distribution systems performance using performance measures,
and develop guidelines for utility managers to (1) evaluate the overall condition of their
distribution systems, (2) establish target levels of performance and (3) identify system
improvements needed to achieve these target levels. Based on the analysis of data from
various water systems, the following goals for water main breaks and leakage are
recommended:
o Main breaks – no more than 0.25 to 0.30 breaks/mi/year (0.16 to 0.19 breaks/
km/year).
o Water leakage – no more than 4,000 to 6,000 gal/d/mi (9.6 to 14.4 m3/d/km)
Water main breaks are defined as water transmission or distribution pipeline breaks.
Typically, service connections to the water user from the water main are not considered
to be water mains.
When the performance measures for water main breaks are exceeded, possible action
scenarios would include rehabilitation of the water main, replacement of the water main,
a leak repair program, an external corrosion control program, and/or an internal corrosion
control program.
The main break recommendation of 0.25 to 0.30 breaks/mi/year (0.16 to 0.19 breaks/
km/year) in the study was for all pipe types, both metallic and non-metallic. The various
pipe materials such as steel and ductile iron were not specifically identified in this report.

•

EPA 600/R-02/029 Decision-Support Tools for Predicting the Performance of Water
Distribution and Wastewater Collection Systems; 2002.
This report summarizes the Environmental Protection Agency’s efforts to identify and
describe European practices that managers are using to make rehabilitation decisions
(performance indicators) and the non-hydraulic models for predicting failures and
managing and optimizing the operation and maintenance of water distribution and
wastewater collection systems. Additionally, this report recommends a conceptual
framework for developing a standardized national database that could maintain
performance indicators related to pipe failures, their causes, repair costs and other
important factors. The proposed modeling efforts would require performance indicators
such as pipe material, pipe age, section length, number of breaks or bursts, and diameter.

32

Corrosion Considerations for Buried Metallic Water Pipe

4.4.2 Interpretation of Historical Performance Data Reviewed
The historical performance data for steel and ductile iron pipe is at best fragmentary as noted by
EPA’s document described above and as shown in table 6. Reclamation’s failures/mile/yr for
both steel and ductile iron pipes are shown below as well as the AWWARF guidelines and the
National Research Council of Canada values for ductile iron pipe.
The data is somewhat limited in the Reclamation study. For example, Reclamation’s ductile iron
data is limited to a total length of 15,794 feet (about 3.0 miles). Reclamation began using ductile
iron pipe in the late 1970s. Conversely, Reclamation has used steel pipe in above-ground
installations since the mid 1920s (Specification No. 361, dated October 20, 1924) and in buried
installations since 1940 (Specification, Number 1420-D, dated September 11, 1940).
The 1995 National Research Council of Canada study did not examine steel pipe. Ductile iron
pipe, as well as other pipe types, was examined and ductile iron had the highest number of
breaks per mile per year of the pipe materials examined in their study. However, this study did
not collect age data or the cause of the breaks for the pipes examined, so the results may not
provide the full performance picture of each pipe type over time.
The 2002 AWWARF No. 90677 report did not provide a distinction between pipe materials in
their study. The value cited by AWWARF is a guideline or a benchmark for assessing the
performance of a water utility.

4.4.3 Historical Performance Conclusions
Data on the historical performance of steel and ductile iron pipe is somewhat limited. As pointed
out in EPA 600/R-02/029, “Decision-Support Tools for Predicting the Performance of Water
Distribution and Wastewater Collection Systems,” a framework is needed for developing a
standardized national database for performance indicators related to pipe failures, their causes,
repair costs and other important factors.
Ductile iron pipe has a thicker wall than steel pipe for a given pressure rating. Therefore, the
results of the 1994 Reclamation study showing a lower failure rate for ductile iron pipe appears
reasonable based on the pipe wall thickness and the age of the installed ductile iron pipelines
versus the age of the installed steel pipelines.
Given the limited and somewhat fragmented nature of the available data on failure rates noted
above, Reclamation does not believe there is sufficient cause to conclude there is a significant
difference in the performance expectations of steel and ductile iron pipe.

33

Corrosion Considerations for Buried Metallic Water Pipe

Table 6.—Summary of Collected Reports and Data

Number of
Failures

Length
(Feet)

Composite Age =
Length x Age / Sum
(Length)

Failures Per Mile
Per Year

0

15,794

11.0

0.0000

277

626,844

42.8

0.0545

Ductile Iron Pipe

23

667,917

10.2

0.0179

Steel Pipe

24

873,374

22.8

0.0064

Ductile Iron Pipe

23

683,711

10.2

0.0175

Steel Pipe

301

1,500,218

31.2

0.0340

Item
Bureau of Reclamation Report Number:
R-94-12 Historical Performance of Buried
Water Pipelines
Reclamation Data
Ductile Iron Pipe
Steel Pipe

AWWARF Data

Combined Reclamation and AWWARF Data

National Research Council of Canada A-7019.1 Final Water Mains Breaks Data on
Different Pipe Materials for 1992 and 1993
Ductile Iron Pipe

0.15 breaks/mile/year
(0.095 breaks/km/year)

Other Considerations
AWWARF recommends
a goal for limits on water
main breaks to 0.25 to
0.30 breaks/mile/year
(0.16 to 0.19 breaks/
km/year) for pipe.
Separate goals for water
main breaks by pipe
material were not
discussed in the study.

AWWARF Report No. 90677 – Distribution
System Performance Evaluation

34

Corrosion Considerations for Buried Metallic Water Pipe

4.5 Expected Service Life
During the design process the selection of materials or products is generally based on
engineering material properties and life cycle expectations. Typically, life cycle design involves
the identification of project service life and product service life. However, expected service life
of a product should not be confused with economic life. For example, Reclamation typically
uses 40 years for economic life, which represents the time for repayment of the project’s loans,
and at least 50 years for the expected service life of a pipe. This section summarizes
Reclamation’s findings regarding expected service lives of steel and ductile iron pipe.

4.5.1 Reclamation Information on Expected Service Life
The following Reclamation reports and data were examined:
•

Replacements: Units, Service Lives, Factors, Prepared for U.S. Department of the
Interior Bureau of Reclamation and U.S Department of Energy Western Area Power
Administration, May 1989.
This document summarizes services lives for 13 different types of pipe material when
designing pipelines for water conveyance. Steel and ductile iron pipes are included in the
13 different types of pipe. According to this report, steel and ductile iron pipes will have
similar service lives. The report also concludes that pipes of all types will give
satisfactory service for a period exceeding 50 years if properly installed and protected.
Generally, CP is provided on steel and ductile iron pipelines where a corrosive
environment is present.

4.5.2 Literature Review on Expected Service Life
The following reports and data were examined:
•

EM-1110-2-2902 U.S Army Corps of Engineers Engineering and Design Conduits,
Culverts and Pipes; October 31, 1997.
The engineering manual provides discussion on project, economic, and product service
lives. The economic service life is typically projected for 50 to 75 years. The product
service life for corrugated steel pipe is at least 50 years provided the coating is applied
properly.

35

Corrosion Considerations for Buried Metallic Water Pipe

•

“Ductile Iron Corrosion Factors to Consider and Why,” by William Spickelmire; ASCE
2003 Proceedings of the ASCE International Conference on Pipeline Engineering and
Construction.
This paper provides a discussion of an analysis using a 60-year service life cycle cost for
24-inch steel and ductile iron pipes. The document provides a discussion on the typical
forecasted life cycle costs for steel and ductile iron pipelines with corrosion costs
factored for a 60-year period.
Additionally, according to the document, “The life-cycle cost analyses and our
experience indicates that ductile iron’s heavier wall allows it to outlast steel, given equal
corrosion measures in aggressive soils. Conversely, in the most aggressive soils, coated
steel with CP will provide a longer life than polyethylene encased ductile iron with or
without CP. In aggressive soils, ductile iron with only PE encasement will have a shorter
life than cathodically protected ductile iron with either PE encasement or bonded
dielectric coating.”

•

Toronto Staff Report to Works Committee; Dated September 28, 2001.
This document was created to report on the Water and Wastewater Services long-term
sewer and water main infrastructure renewal needs. According to this document, “Cast
iron water mains were assumed to have life expectancies in a range from about 60 to
100 years, while ductile iron water mains were assumed to have life expectancies in a
range from about 50 to 70 years.”

•

E-Mail messages from Mike Woodcock (Washington Suburban) to James Keith
(Reclamation) 3/11/04.
Mike Woodcock works for Washington Suburban as a metallurgist. Several e-mail
messages from Mr. Woodcock were received, and excerpts from them are included in
appendix C. His comments generally indicated that service life predictions are
theoretical in nature because their oldest ductile iron pipe has not been in the ground long
enough to establish a service life. He also stated that he expects to see increasing
corrosion problems on ductile iron pipe from this time forward.

4.5.3 Conclusions on Expected Service Life
Reclamation has been able to establish statistically-based service life expectations for a wide
variety of equipment and pipelines and concluded that steel and ductile iron pipes will give
satisfactory service for a period exceeding 50 years. It is likely with the use of CP on steel and
ductile iron pipes, the service life will be extended beyond that of pipes with coatings only. The

36

Corrosion Considerations for Buried Metallic Water Pipe

City of Toronto’s Water and Wastewater Services are assumed to have life expectancies in a
range from 50 to 70 years for ductile iron water mains. However, it should be noted that
according to available documents, ductile iron pipe has only been used in the United States since
the 1960s for water transmission and distribution systems.
Based on all of the information obtained, it is reasonable to assume that a minimum anticipated
service life for steel and ductile iron pipes of 50 to 70 years is achievable (see table 7).

4.6 Life Cycle Costs
4.6.1 General
Life cycle costs for a pipeline project include initial capital costs as well as periodic operation,
maintenance, replacement and energy (OMR&E) costs incurred throughout the economic life of
the project. This section of the report provides guidance for Reclamation designers on how to
evaluate key OMR&E costs for a pipeline project and how to incorporate differences in those
costs for various pipe options into a construction contract through a bid adjustment or other
means.
Key components of the OMR&E costs for a pipeline system are costs associated with pumping
and cathodic protection systems, the major component being the cost of power required for
pumping. Due to differences in manufacturing, ductile iron pipe is typically supplied in slightly
larger inside diameters than steel pipe for the same nominal diameter. This larger diameter
allows the water within the pipe to flow at a lower velocity reducing hydraulic pressure losses
which, in turn, allows the same flow of water to be supplied using less energy to pump the water.
Reclamation designs pipelines to meet the hydraulic performance requirements of each project in
the most economical manner practicable. During the design phase of a project, Reclamation
evaluates pipe diameters, pumping plant configurations, and hydraulic transient control features
to meet the hydraulic performance requirements of the project. Initial capital costs for these
features are compared to major operational costs such as energy costs for pumping to obtain the
lowest life cycle cost of the pipeline system. This process leads to the most economic
combination of pipe diameters along the pipeline’s alignment which are included in the
construction specifications.
Reclamation’s construction contracts contain a provision under which a bidder may substitute
other combinations of actual inside pipe diameters (which match the manufacturing techniques
of the pipe-type being bid) as long as the proposed combination of pipe diameters meets the
hydraulic performance requirements of the project. This contract provision effectively removes
any difference in pumping costs between pipe options. Therefore, differences in pumping costs

37

Corrosion Considerations for Buried Metallic Water Pipe

Table 7.—Service Life Recommendations
Item

Years

Project Service Life
Reclamation’s economic life

40

Army Corps economical analysis

50 to 75

Army Corps major infrastructure projects

100

Product Service Life
Steel Pipe
Steel pipe service life exceeds 50 yrs ("Replacements units, service
lives, factors", Bureau of Reclamation, FIST)

50

Steel at least 50 yrs for most environments with coatings (USACE)

50

Washington Suburban (Mike Woodcock metallurgist)
Oldest 30 inch no cathodic protection and coal tar enamel

50 to 60

Oil and gas steel pipes

50 to 100

Ductile Iron Pipe
Ductile iron pipe service life exceeds 50 yrs (“Replacements units,
service lives, factors,” USBR, FIST)

50

Toronto Water and Wastewater Division (September 28, 2001)

50 to 70

Life cycle cost from 2003 ASCE Pipe Conference - “Ductile Iron
Corrosion Factors to Consider and Why” by William Spickelmire

60

Washington Suburban (Mike Woodcock metallurgist)
Unwrapped

35

Polyethylene encased pipe

40 to 45

European practices (zinc/aluminum spray coat, epoxy top coat plus
polyethylene encasement)

100

Blast clean off magnetite coating and coat with either fusion bond
epoxy or coat with extruded polyethylene coating and then add CP

100

Recommendations
Both products contain approximately the same amount of iron (roughly
95-percent) iron (FE). Therefore, it is expected that both materials will
react similarly to corrosive environments.
Steel

50 to 70

Ductile iron

50 to 70

38

Corrosion Considerations for Buried Metallic Water Pipe

between pipe options with different inside diameters are not included in this life cycle cost
analysis. This section does provide an example of how to estimate costs associated with a
cathodic protection system in a construction contract.
Another component of a pipeline project’s OMR&E costs relates to the periodic cost of repairs
of the pipe over the life of a project. As noted in section 4.4.3 of this report, Reclamation has
not found sufficient cause to conclude there is a significant difference in the performance
expectations of steel or ductile iron pipe. Since these costs would be very similar for both pipe
options, the estimated costs of expected repairs are not included in this life cycle cost analysis.
Another component of a pipeline project’s OMR&E costs relates to the replacement of the
pipeline itself. As noted in section 4.5.3 of this report, Reclamation has not found compelling
data to conclude any significant difference in the anticipated service lives of properly designed,
manufactured, installed, and maintained steel or ductile iron pipelines. Since pipeline
replacement costs for either pipe option would not be incurred during the economic life of
the project, these costs are not included in this life cycle cost analysis.
Cathodic protection OMR&E costs include the costs of energy, replacement costs for the anode
beds, and operation and maintenance costs. These costs vary by pipe type, coatings, and other
factors. These costs are not normally included in the bid documents.

4.6.2 Impact on Bid Prices
The Federal Acquisition Regulations (FAR) promote full and open competition or maximum
practicable competition and “only includes restrictive provisions or conditions to the extent
necessary to satisfy the needs of the agency or as authorized by law”.7
All technically acceptable pipe options are evaluated for use on Reclamation projects. Any
practice that eliminates competition has the ability to raise capital costs for a given project.
When comparing two material types, one would expect competition among the different pipe
material types as well as competition between similar pipe material types. Many factors other
than competition will also affect the bid price to the owner and the supplier’s price to each
contractor. Factors affecting prices include but are not limited to the following: quantity,
location, current supply and demand, market fluctuations in raw materials, business overhead
and profit, etc. Quantifying the true effects of eliminating a material type from competition
would be difficult, but it would be fair to conclude that over time, costs could be expected to
increase if only one type of material is allowed to compete for the work.

7

FAR 2001-15 August 25, 2003 11.002 Policy. (a)(1)(ii).

39

Corrosion Considerations for Buried Metallic Water Pipe

4.6.3 Life Cycle Cathodic Protection Costs
A comparative project present worth analysis was performed to evaluate annual costs between
steel and ductile iron pipe options for a generic pipe system. The initial costs of furnishing and
installing pipe and CP systems are usually not included in the life cycle cost study. The time
period or service life evaluated was 50 years. The costs included in this evaluation were the
following: 20 and 40 year replacement costs of the CP system, annual operation of the CP
system, and annual maintenance costs of the CP system.
This study utilized assumptions that would be consistent with typical Reclamation projects. The
comparison shown in table 8 is not intended to cover all possible scenarios, but instead to give
the reader some indication of the order of magnitude of the costs, and a meaningful comparison
for a generic project.

Table 8 - Bid Adjustment Worksheet
Note: This is an example only. Costs will vary greatly depending on the actual requirements of an
individual system and appropriate factors applied by the designers.
Pipe System
Diameter
Distance
Soil Resistivity
Average Pressure

Units
36 Inches
10.00 Miles
1,500 ohm-cm
150 PSI

Factors:
Life Cycle
Real Interest Rate *
Cost of Power

Units
Years
Percent
/kWh

50
3.50%
$0.06

Pipe Option Bid
Ductile Iron Pipe With
Steel Pipe With
PE Encasement
Dielectric Coating
Estimated Cathodic Protection
Cost/Bed

$

$35,000 /Anode Bed

Beds

2

Beds

$70,000 **

1

Beds

$35,000 **

Present Worth Replacement

PWF

Duration

20

Year

$35,180

20

Year

$17,590

Present Worth Replacement

PWF

Duration

40

Year

$17,680

40

Year

$8,840

Annual Cathodic Protection O&M

Annual

$1,600
$400
$2,000
$46,911

40 Hours/Yr

$110.10

33

Labor
$20
Non Labor
Total

80 Hours/Yr

PWA
Annual Power Requirements

Annual

1835

kWh

PWA
Total adjustment

Totals

* OMB Circular #A-94
** Because these costs are included in the bid documents, they are not included in bid adjustment

40

kWh

$800
$200
$1,000
$23,456
$1.98

$2,582

$46

$102,353

$49,932

Corrosion Considerations for Buried Metallic Water Pipe

Table 8 shows an example of how Reclamation might utilize life cycle costs as performance
evaluation criteria to award a technically acceptable pipe option. This would result in the best
value to the Government over the life of the project, and not just the best value at the time of
award.
An economic analysis would need to be performed for each project to see if a bid adjustment was
warranted. There are many technical factors that go into the design of a cathodic protection
system which in turn affect expected life cycle costs. If warranted, a bid adjustment would take
into account the OMR&E costs associated with the cathodic protection system and coatings
required for different pipe options used in the specifications.
The costs required for CP depend on the type of pipe and coating selected. A pipe type with a
larger surface area of metal will require more current to polarize the metal and provide sufficient
corrosion protection. When comparing coatings on steel and ductile iron pipe, the ductile iron
pipe with PE encasement requires much more current than steel pipe with a tape wrap coating.
Therefore, the ductile iron pipe will usually require additional anode beds to be placed along the
alignment as compared to the number of beds required for steel pipe. The costs for the original
ground beds will be reflected in the capital cost bid for each pipe alternative. However, the
power, maintenance and replacement costs (every 20 yrs) are not currently reflected in the
original capital cost of the project.
If warranted, the differences in the identifiable OMR&E costs between steel and ductile iron pipe
should be reflected in the contract award decision. This can be accomplished by using OMR&E
life cycle costs as performance evaluation criteria when awarding a contract. Appropriate
OMR&E present worth costs associated with the pipe type chosen by each bidder would be
added to that bidder’s “Total for Schedule” to evaluate the 50-year cost of the project. This
process would not eliminate competition, but would allow Reclamation to utilize life cycle costs
as performance evaluation criteria in awarding contracts. The contract would then be awarded to
the bidder which represented the best overall value to Reclamation.

4.7 Peer Review of Reclamation Corrosion Protection Strategy
The review panel that was convened by Reclamation in March of 2004 was also asked to peer
review Reclamation’s updated Corrosion Prevention Criteria and Requirements. Their specific
input on this issue is included in appendix D. On April 6, 2004, Reclamation and the panel
developed a consensus on the following key points regarding the corrosion prevention criteria
and requirements:
•

Steel and ductile iron pipe should be installed with some form of coating. No bare pipe
should be allowed.

•

All metallic pipe installed should be electrically continuous.

41

Corrosion Considerations for Buried Metallic Water Pipe

•

Soil resistivities are a good indicator of a soil’s corrosion potential.

•

Other factors in addition to soil resistivities should be evaluated when designing a
corrosion protection system. These factors include, but are not limited to, performance
history, stray current exposure, pH, sulfates, chlorides, criticality of the pipeline, design
conservatism, and specific client requests.

•

Polyethylene encasement is not a true coating.

•

Polyethylene encasement can be used on ductile iron in less corrosive environments.

•

Bedding and backfill can be critical to the successful use of PE encasement.

•

The panel has no knowledge of corrosion failures where PE encasement was used in
conjunction with CP.

•

The panel believes the table suggested by Reclamation may be slightly conservative, but
they feel an agency should use whatever corrosion mitigation methods with which it is
comfortable.

•

The panel believes Reclamation has little choice other than to rely on past experience and
establish a conservative guideline that the bureau can consistently follow.

•

The panel supports a conservative approach by Reclamation for the design, construction,
and monitoring of public sector water projects.

•

A bid adjustment for CP should be considered during design.

•

The performance of PE encasement on ductile iron pipe is not adversely affected by the
diameter of the pipe.

5.0 BURIED CONCRETE PIPE WITH STEEL REINFORCEMENT
The data reviewed for steel and ductile iron pipe during the preparation of this report indicated a
need to review the corrosion prevention criteria for concrete pipe with steel reinforcement.
Concrete pipe relies on the alkalinity present in concrete or mortar coating to encapsulate the
steel in a passivated environment that will prevent corrosion. Intimate contact is required
between the steel and the concrete or mortar coating.

42

Corrosion Considerations for Buried Metallic Water Pipe

Mortar coatings are used to protect the steel rod in pretensioned concrete cylinder pipe and to
protect the steel wire in prestressed concrete pipe. Mortar is applied pneumatically to the outside
of the pipe as it is spun. Reclamation has required that mortar coated pipe be cathodically
protected in corrosive soil conditions since 1990.
Reclamation has experienced corrosion- and cathodic protection-related problems on two major
prestressed concrete pipe projects. As a result, Reclamation placed a moratorium on the use of
prestressed concrete pipe for Reclamation projects in 1990. This pipe option has therefore been
removed from the corrosion table until the issues related to the moratorium have been addressed.
Corrosion problems have also been noted around the country with the use of pretensioned
concrete cylinder pipe in corrosive soils. However, the corrosion can easily be controlled with
the proper application of CP.
Steel reinforcement encased in high-quality dense concrete (as is the case in reinforced concrete
pipe) has long been considered to be well protected from corrosion. In recent years, concerns
about concrete’s vulnerability to penetration by dissolved salts (chlorides and sulfates) to the
depth of the reinforcement led Reclamation to recommend additional corrosion protection
measures for reinforced concrete pipe installed in severely corrosive soils.
As noted earlier in this report, there is no definitive threshold level of soil resistivities where soil
conditions go from mildly corrosive to severely corrosive. Based on the previous discussion in
this report, Reclamation has decided to be consistent with the type of protection provided for all
types of buried metallic pipe. Therefore, 3,000 ohm-cm soil resistivity was selected as the
dividing line between mildly corrosive and severely corrosive conditions for concrete pipe with
steel reinforcement.
Therefore, concrete pipe installed in soils with resistivities less than 3,000 ohm-cm require a
dielectric coating over the concrete or mortar coating in conjunction with CP. Concrete pipe
installed in soils with resistivities greater than or equal to 3,000 ohm-cm do not require a
dielectric coating over the concrete or mortar but, except as noted below*, will require a
corrosion monitoring system.
* Note: Reinforced concrete pipe can be manufactured with or without steel joint rings.
It is difficult, but not impossible, to electrically connect pipe units without steel joint
rings. This characteristic severely limits the ability to construct an electrically continuous
pipeline out of such pipe units. Given Reclamation’s good historical experience with
reinforced concrete pipe installed in mildly corrosive soils, the requirement for corrosion
monitoring (and the resulting need to construct an electrically continuous pipeline) in
soils with resistivities above 3,000 ohm-cm is waived for reinforced concrete pipe
manufactured without steel joint rings.
As for all buried metallic pipe, evaluation of all soil conditions should be considered in the final
corrosion prevention design. Corrosion prevention measures may vary on a given project based
on differing conditions along the alignment.
43

Corrosion Considerations for Buried Metallic Water Pipe

6.0 RECOMMENDATIONS
6.1 Corrosion Provisions
The updated Corrosion Prevention Criteria and Minimum Requirements are outlined in table 2.
These criteria are designed to provide minimum requirements to determine a corrosion design for
a pipeline based on soil resistivities along the pipeline alignment. The criteria are not intended to
replace good engineering judgment. As an example, the 25-point table, as recommended by
corrosion engineer Bill Spickelmire in the Lewis and Clark Rural Water System Draft Report,
considers many other factors, such as required service life, pipe size, hydraulic transient
pressures, and pipe location when determining the amount of corrosion protection required for a
pipeline. All these factors can be examined on a case-by-case basis, but table 2 will provide a
good starting point from which to begin the corrosion design process for a specific pipeline
application.
Previous versions of Reclamation’s Corrosion Prevention Criteria and Requirements (see
table 1) reflected differing levels of conservatism in the design of corrosion mitigation for a
given pipeline installation depending on the type of deliveries serviced by the pipeline. For a
given set of soil resistivities, more conservative corrosion measures were required for a
municipal and industrial (M&I) system than for an irrigation system. This approach was
intended to reflect a higher level of consequences of failure for an M&I system vs. an irrigation
system.
Given the shifting focus of Reclamation’s water delivery projects from purely irrigation systems
towards more M&I systems, and the reallocation of water from irrigation to M&I, this distinction
no longer seems prudent. Also, a reduction in future OMR&E costs needs to be considered no
matter what type of system is being built. Therefore, Reclamation’s update of its Corrosion
Prevention Criteria and Minimum Requirements will adopt a single set of corrosion mitigation
recommendations based on pipe materials and soil conditions regardless of the type of system
being designed.
Other updates to the Corrosion Prevention Criteria and Minimum Requirements table, as shown
in table 2, are discussed below:
Bonded coating and CP are required for ductile and steel pipes that pass through soils with lower
than 2,000 ohm-cm resistivities. The rationale for using a resistivity of 2,000 ohm-cm as the
cutoff is based in part on the 10-point system used to determine the possibility of pipeline
corrosion. This system appears in DIPRA literature as well as the appendices of ASTM A888
and AWWA C105. The tables indicate that soils with lower than 2,000 ohm-cm resistivities are
more likely to cause corrosion than higher resistivity soils. These tables use the lowest resistivity
found during testing and award points from 0 to 10 based on the precise resistivity. NACE
classifies soils with resistivities from 1,000 - 2,000 ohm-cm as moderately corrosive, and the
AWWA M11 Steel Pipe Manual classifies soils with resistivities from 0 – 2000 ohm-cm as bad.
44

Corrosion Considerations for Buried Metallic Water Pipe

These corrosive conditions dictate the use of a conservative design for the pipe protection
in these soils to provide a minimum 50-year life.
Because there is conflicting information as to the effectiveness of CP on ductile iron pipe with
PE encasement, it seems prudent to not allow the use of PE encasement under severe corrosion
situations. Therefore, for these soil conditions, the use of pipe with a bonded coating and CP
will be required. This coating system will also reduce the annual cost of power associated with
protecting a pipeline in this environment. Exterior mortar or concrete coatings on steel pipe
should be used in these environments only with a coal tar epoxy seal coat. The epoxy coating is
assumed to provide a bonded coating to the mortar or concrete.
The use of 2,000 ohm-cm in table 2, based on field measurements, is a good break point for the
cutoff from soils with definite severe corrosion risks as opposed to more benign soils with
greater resistivities. By assuming that the soils less than 2,000 ohm-cm are definitely corrosive
and will require the best protection possible (bonded dielectric coating and CP), there is very
little need for any further soil analysis of the pipeline alignment. Conversely, where the soil
resistivities are greater than 2,000 ohm-cm, the soils are often less aggressive, and the minimum
level of corrosion protection required for the pipeline could be lower than that required in the
more corrosive soils. Because bonded dielectric coatings are not automatically required for these
soils, more soil tests should be performed to ensure that there are not any other conditions which
could cause severe corrosion.
Soil resistivity ranges from 2,000-3,000 ohm-cm are generally classified as moderately corrosive.
Because the data and information about the exact cutoff point from severe corrosion conditions
to mild corrosion conditions are not perfect, it seems prudent to provide some form of dielectric
coating on the pipe (bonded or unbonded), and CP to ensure the longevity and lower maintenance
costs over the life of the project. Based on the data reviewed during the preparation of this
report, Reclamation believes PE encasement for ductile iron pipe and coal tar epoxy seal coat on
mortar coated steel or concrete pipe should be satisfactory to reduce long-term CP power costs.
For soil resistivities greater than 3,000 ohm-cm, the chance of corrosion diminishes, and bonded
coatings and CP are normally not required. Corrosion monitoring and joint bonding should be
provided in case corrosion becomes an issue and CP is required later.
The above discussion about soil resistivities does not address the need for the evaluation of soils
for other corrosion factors such as the presence of pH, sulfates, chlorides and stray current
interference from adjacent pipelines or other features. In addition, an evaluation of the use, ease
of access, pressure requirements, and other pertinent information, similar to the 25-point system
used by some water utilities, should be considered. These factors should always be included in
the determination of a corrosion protection design, regardless of soil resistivity.
While the overall corrosion prevention methods for a pipeline are based, in part, on a 10 percent
probability of encountering soils with a given resistivity, each project should be evaluated to
determine if greatly differing soil conditions occur along the alignment. If certain locations
differ greatly from others, the corrosion prevention methods should be adjusted accordingly.
45

Corrosion Considerations for Buried Metallic Water Pipe

In August of 2002 DIPRA announced that the eight leading manufacturers in North America will
no longer honor a warranty for ductile iron pipe with any exterior dielectric coating other than
polyethylene encasement.8 In corrosive soil conditions, this could result in decreased
competition, as the number of available pipe options will decrease. This in turn could result in
higher capital costs, because project bids are usually more competitive when there is more than
one pipe type option. But not every pipe type will work on every project, due to size limitations
or pressure requirements, so it is not unusual to have a pipe type eliminated from consideration
because it cannot meet the needs of the user.
With regard to life cycle costs, Dr. Graham Bell proposed in the April 6, 2004 review panel
discussion with Reclamation that more than $3.00/ft2 should never be spent for a coating, as this
will become uneconomic when compared to the power costs required to protect a bare pipeline
with CP. He explained that this is why PE encasement is so popular with ductile iron pipe
installers. A typical dielectric coating can easily cost more than $3.00/ft2 for larger diameter
pipes. Bonded dielectric coatings for smaller pipes (24-inch diameter and less) typically have
costs less than $3.00/ft2. Because a larger pipe carries more flow then a smaller pipe, the
consequences of failure are greater to the user when there is a pipe failure. Repair costs are
greater, and more people will probably be affected by the shutdown. Because smaller diameter
pipes have lower coating costs and larger diameter pipes are more critical to keep in service,
Reclamation feels that in a corrosive environment, the use of both CP and a bonded dielectric
coating should be used for all diameters of pipe. Typical costs for exterior coatings are listed in
appendix E.
The review panel also suggested the use of rounded or small aggregate size backfill about the
pipe, such as sand or 1/4-inch minus material. This would help prevent damage to the PE
encasement during placement of the backfill material. Determination of available materials for a
project is site-specific. Importation of sand or 1/4 -inch minus material may be expensive and
uneconomic for a specific project. The installation design of the pipe may not allow the use of
sand due to high ground water and possible migration of materials over time. Therefore, the type
of backfill should be considered where PE encasement is being used, but should not be an
overwhelming driver in the corrosion design. CP can always be added later if the monitoring
shows that corrosion is occurring from damage to the PE encasement.

6.2 Bid Adjustments
Some water utilities have utilized bid adjustments to account for economic differences as a result
of various pipe types and coatings necessary in corrosive soils. Utilizing localized historical
data gathered on various pipe and coating options, costs have been developed to account for
OMR&E differences as a result of the various pipe and coating combinations. A capital cost
adjustment is applied during the procurement process to account for the OMR&E historical
differences.
8

Infrastructure Preservation News, Vol. 1, No. 2, June 2003. “Assessing DIPRA’s New Corrosion Protection
Standards.”

46

Corrosion Considerations for Buried Metallic Water Pipe

Reclamation does not have specific data relevant to the life (repairs) of the pipe that represents
the many locations in the western United States where one might find the need to require a CP
system, and therefore uses a more conservative approach to corrosion design. Expected life
cycle costs associated with the OMR&E of the CP system can, however be analyzed and
addressed using a bid adjustment.
If warranted, a bid adjustment will allow Reclamation to obtain the lowest life cycle costs and
not just the lowest capital cost. Specifications would include criteria utilized to evaluate
contractor’s proposals not only for capital costs but also for life cycle costs associated with a CP
system. The contract would be awarded to the offeror that represented the best overall value to
Reclamation and its stakeholders.

6.3 Updates to the Corrosion Prevention Criteria and
Requirements Table
Table 2 outlines Reclamation’s current (July 2004) corrosion prevention criteria and minimum
requirements.9 Application of the table’s criteria and requirements shall be in accordance with
the Reclamation Manual Policy “Performing Design and Construction Activities” (FAC P03).
The updates to the table are as follows:
1. The table title has been changed to reflect that these are minimum corrosion
requirements.
2. The distinction between irrigation pipelines vs. M&I pipelines has been removed. The
same corrosion prevention criteria and requirements now apply to all Reclamation
pipelines.
3. The pipe size and weight restrictions for the use of PE encasement on ductile iron pipe
have been removed from the table.
4. The soil resistivity values for the minimum required corrosion protection measures for
pipelines have been revised:
•

9

For steel and ductile iron pipe, a bonded dielectric coating and cathodic
protection is required for soil resistivities ≤ 2,000 ohm-cm, an unbonded coating
(PE encasement for ductile iron pipe and cement mortar with coal tar epoxy for
steel pipe) and cathodic protection is the minimum requirement for soil
resistivities between 2,000 and 3,000 ohm-cm; and an unbonded coating (PE
encasement for ductile iron pipe and cement mortar for steel pipe) and corrosion
monitoring is the minimum requirement for soil resistivities ≥ 3,000 ohm-cm.

Table 1 outlines the corrosion prevention criteria and requirements updated on April 23, 2003.

47

Corrosion Considerations for Buried Metallic Water Pipe

•

For pretensioned concrete pipe, mortar coating with coal tar epoxy and cathodic
protection is required for soil resistivities < 3,000 ohm-cm, and mortar coating
and corrosion monitoring is the minimum requirement for resistivities
≥ 3,000 ohm-cm.

•

For reinforced concrete pipe, concrete coating with coal tar epoxy and cathodic
protection is required for soil resistivities < 3,000 ohm-cm, and concrete coating
and corrosion monitoring on pipe with steel joint rings is the minimum
requirement for resistivities ≥ 3,000 ohm-cm.

5. The cutoff point for increased corrosion protection for pretensioned and reinforced
concrete pipe was reduced from 4,000 ohm-cm to 3,000 ohm-cm.
6. Prestressed concrete pipe has been removed from the table. Reclamation has had a
moratorium on the use of this type of pipe since 1990. If and when this changes,
corrosion mitigation measures for prestressed concrete pipe will be added to this table.

7.0 REFERENCES
Bell, G., 2003. MJ Schiff and Associates, Inc. Personal communication with Tom Johnson of
the Bureau of Reclamation.
Bonds, R.W., August 1997. “Stray Current Effects on Ductile Iron Pipe.” Ductile Iron Pipe
Research Association.
Brander, R., 2001. “Water Pipe Materials in Calgary, 1970 – 2000,” American Water Works
Association - Infrastructure Conference Proceedings.
Clark, C.M., October 1972. “Stray and Impressed Current Tests on Polyethylene-Encased Cast
Iron Pipe,” presented at the National Association of Corrosion Engineers Western Region
Conference.
FHWA, 2001. Corrosion Cost and Preventive Strategies in the United States, Report
No. FHWA-RD-01-156, Federal Highway Administration, McLean, Virginia.
Fitzgerald, J.H, August 1968. “Corrosion as a Primary Cause of Cast-Iron Main Breaks,” In
American Water Works Association, vol. 60, No. 8, pp. 882 – 897.
Fogata, M., 2003. City of San Diego, California. Personal communication with Tom Johnson of
the Bureau of Reclamation.
Garrity, K.C., C.F. Jenkins, and R.A. Corbett, August 1989. “Corrosion Control Design
Considerations for a New Well Water Line.” In Materials Performance, pp. 25 – 29.
48

Corrosion Considerations for Buried Metallic Water Pipe

Infrastructure Preservation News, vol. 1, No. 2, June 2003. “Assessing DIPRA’s New Corrosion
Protection Standards.”
Kroon, David H., Dale Lindemuth, Sheri Sampson, and Terry Vincenzo, Corrpro Companies
Inc., 2004. NACE International, Paper No. 04046, “Corrosion Protection of Ductile Iron
Pipe.”
Lieu, D. and M.J. Szeliga, July 2002. “Protecting Underground Assets with State-of-the-Art
Corrosion Control.” In Materials Performance, pp. 24-28.
Lisk, I., January 1997. “The Use of Coatings and Polyethylene for Corrosion Protection.” In
Water Online.
Noonan, J.R., June 1996. “Proven Economic Performance of Cathodic Protection and
Anticorrosion Systems in the Water Pipeline Industry,” Bulletin No. 6-6, Steel Plate
Fabricators Association, Des Plaines, Illinois.
Pimentel, J.R., July 2001. “Bonded Thermoplastic Coating for Ductile Iron Pipe.” In Materials
Performance, pp. 36 – 38.
Romanoff, M., 1957. “Underground Corrosion.” In National Bureau of Standards Circular 579,
U.S. Government Printing Office, Washington D.C.
__________, June 1968. “Performance of Ductile-Iron Pipe in Soils.” In American Water
Works Association, vol. 60, No. 6, pp. 645 – 655.
RUSTNOT Corrosion Control Services, Inc. October 2003. “Corrosion Control Predesign
Report, Lewis and Clark Rural Water System (Draft).”
Schiff, M.J. and B. McCollom, 1993. “Impressed Current Cathodic Protection of Polyethylene
Encased Ductile Iron Pipe,” Paper No. 583, presented at Corrosion93, The NACE Annual
Conference and Corrosion Show.
Smith, W.H., May – June 1963. “A Report on Corrosion Resistance of Cast Iron and Ductile
Iron Pipe.” In Cast Iron Pipe News, vol. 35, No. 3, 16 – 29.
__________, 1970. “Cast Iron Pipe Design, Environment, Life,” Printed from Journal of the
New England Water Works Association, vol. 84, No. 4.
Spickelmire, B., July 2002. “Corrosion Considerations for Ductile Iron Pipe.” In Materials
Performance, pp. 16 – 23.
Stroud, T.F., April 1989. “Corrosion Control Measures for Ductile Iron Pipe,” Paper No. 585,
Presented at Corrosion89.
49

Corrosion Considerations for Buried Metallic Water Pipe

Szeliga, M.J., B.M. Brandish, and G.M. Hart, August 1993. “The Application of Corrosion
Control Methods to Large Diameter Water Mains,” presented at The Tri-Association
Conference, AWWA Chesapeake Section.
Szeliga M.J. and D.M. Simpson, July 2001. “Corrosion of Ductile Iron Pipe: Case Histories.”
In Materials Performance, pp. 22 - 26.
__________, 2003. “Underground Corrosion in the Water and Waste Water Industries,”
presented at the Appalachian Underground Corrosion Short Course.
von Fay, Kurt and Michael Peabody, September 1994. “Historical Performance of Buried Water
Pipe Lines,” Bureau of Reclamation Report No. R-94-12.

50

Table 1
Corrosion Prevention Criteria and Requirements

Pipe Alternative

Ductile Iron

Prestressed
Concrete3
Pretensioned
Concrete

Irrigation

M&I

Corrosion Monitoring
System

Cathodic Protection
System

Polyethylene
encasement1

>15
≤15

>30
≤30

x
x

x

Bonded dielectric2

>10
≤10

>20
≤20

x
x

x

Mortar/coal-tar epoxy

>25
≤25

>50
≤50

x
x

x

Mortar

>20
≤20

>40
≤40

x
x

x

Mortar/coal-tar epoxy

>15
≤15

>30
≤30

x
x

x

Concrete

>20
≤20

>40
≤40

x
x

x

Concrete/coal-tar epoxy

>15
≤15

>30
≤30

x
x

x

Mortar

>20
≤20

>40
≤40

x
x

x

Mortar/coal-tar epoxy

>15
≤15

>30
≤30

x
x

x

Bonded dielectric2

>10
≤10

>20
≤20

x
x

X

External Protection
(Primary/Supplemental)

Reinforced Concrete

Steel

1
2
3

Soil Resistivity – 10% Probability Value
(Σ-m)

Updated April 23, 2003

Applicable to pipe with corrosion allowance, 24-inch inside diameter maximum, and 150 lb/ft maximum.
(NOTE: Given recent pipe industry experience with ductile iron pipe, Reclamation plans to re-examine this provision.)
Bonded directly to metal to be protected.
Reclamation currently has a moratorium on this pipe alternative.

51

Table 2
Corrosion Prevention Criteria and Minimum Requirements1

Pipe Alternative

Soil Resistivity – 10% Probability
Value (ohm-cm)

Corrosion Monitoring

Cathodic Protection2

Bonded dielectric3

YES

YES

> 2,000 ohm-cm < 3,000 ohm-cm

Polyethylene
encasement

YES

YES

≥3,000 ohm-cm

Polyethylene
encasement

YES

NO

<3,000 ohm-cm

Mortar / coal-tar epoxy

YES

YES

≥3,000 ohm-cm

Mortar

YES

NO

< 3,000 ohm-cm

Concrete / coal-tar
epoxy

YES

YES

≥3,000 ohm-cm

Concrete

YES4

NO

≤ 2,000 ohm-cm

Bonded dielectric3

YES

YES

Mortar / coal-tar epoxy

YES

YES

Mortar

YES

NO

≤ 2,000 ohm-cm
Ductile Iron

Pretensioned Concrete

Reinforced Concrete

> 2,000 ohm-cm < 3,000 ohm-cm

Steel

≥3,000 ohm-cm
1
2
3
4

Minimum
External Protection
(Primary/Supplemental)

July 2004

This table should be considered to be the minimum corrosion prevention requirements for a pipeline corrosion design. Additional soil
conditions and risk assessment factors should be considered on a case-by-case basis for each specific project.
OMR&E costs for cathodic protection for each pipe type should be evaluated.
Bonded directly to metal to be protected.
Corrosion monitoring is required for concrete pipe with steel joint rings, but not for concrete pipe with concrete joints.

52

Appendix A
Responses to Review Panel Input

Appendix A
Responses to Review Panel Input
In 2003, Reclamation’s corrosion engineer completed an extensive literature review of over
150 available industry references related to the effectiveness of PE encasement used as part of a
corrosion control sys tem for DIP. The review of this material was documented in a draft report
originally entitled “Corrosion Considerations for Ductile Iron Pipe.”
A Review Panel was convened by Reclamation in March of 2004 to peer review Reclamation’s
evaluation of the effectiveness of unbonded coatings on metallic pipe. The Panel consisted of
two private sector corrosion engineers (G.E.C. Bell, M.J. Schiff & Associates, Claremont, CA;
and R.Z. Jackson, CH2M Hill, Sacramento, CA) and a materials scientist from the National
Institute of Standards and Technology (NIST). (Y. Cheng, Materials Reliability Division,
Boulder, CO). Also included by contract was an independent Panel chair and technical assistant
to serve as a referee to incorporate the panelists’ comments into a peer-reviewed document
(NIST: (C.N. McCowan (Panel Chair) – Boulder; and R.E. Ricker, Metallurgy Division,
Gaithersburg, MD)). The Panel peer reviewed the above draft report, prepared by Tom Johnson
(Reclamation’s corrosion engineer until leaving for a position with another agency in February
of 2004). A copy of the draft report, which includes the panel’s comments, is included in
appendix B. In addition, the Review Panel was asked to provide conclusions to a series of six
questions with regard to corrosion protection practices. The questions and conclusions are
included in appendix D.
The Review Panel provided Reclamation with the following three products:
1. A summary of the discussions by the Review Panel of the Draft Document (included in
appendix B)
2. Specific comments and recommendations on the draft report “Corrosion Considerations
for Ductile Iron Pipe,” (included in appendix B).
3. Panel responses on six questions posed by Reclamation regarding corrosion protection
practices (included in appendix D).
This appendix provides Reclamation’s responses to each of the products listed above.

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Appendix A
Responses to Review Panel Input

Reclamation’s Responses to the Summary of the Discussions by the
Review Panel of the Draft Document
Panel Comment 1. “All of the specific additions suggested for the draft by the reviewers were
agreed to be relevant and were incorporated into the draft in one form or another.”
Reclamation Response: See the responses to the specific comments in the section below.
Panel Comment 2. “Although the draft was considered in detail and specific additions and
changes were made, it is premature to consider that full consensus was reached concerning the
specific language in the draft. (The reviewers did not see the final changes to the draft; there was
not enough time to discuss all the details at the panel meeting).”
Reclamation Response: Reclamation acknowledges the Review Panel’s review of the
draft report. Reclamation has decided to incorporate the draft
report into this Technical Memorandum rather than finalize the
report.
Panel Comment 3: “There was general consensus that the technical details considered in the
existing draft are reasonable and appropriate, but the scope of the document needed to be more
clearly defined and followed. The draft primarily takes a materia l (iron versus steel technology)
view of corrosion on ductile iron pipe and is virtually silent on other design aspects that can
influence the corrosion of these materials (such as back fill).”
Reclamation Response: We agree that the draft report was focused on a material view of
corrosion on ductile iron pipe. The Technical Memorandum
deals with corrosion prevention considerations for all metallic
pipe and covers additional design aspects.
Panel Comment 4. “Many of the specific comments have been incorporated. It was agreed that
this draft needed significant expansion to cover the scope implied by the title. As the scope and
text stand, it was estimated that the document was between 50 and 70 percent ready for submittal
to a peer-reviewed journal. ”
Reclamation Response: As stated above, Reclamation has decided to incorporate the
draft report into a Technical Memorandum rather than finalize
the report.
Panel Comment 5. “Either the scope of the document (and title) needs to be clearly defined and
limited, to better reflect the issues actually discussed in the document, or most of the comments

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Appendix A
Responses to Review Panel Input

in the draft should be developed and incorporated into the document to better address the various
issues that are not covered in the current draft of ‘Corrosion Considerations for Ductile Iron
Pipe’”.
Reclamation Response: As stated above, Reclamation has decided to incorporate the
draft report into a Technical Memorandum rather than finalize
the report. The Technical Memorandum deals with corrosion
prevention considerations in a broader sense.
Panel Comment 6. “There was no disagreement on the first conclusion of the document, that the
use of polyethylene encasement for corrosion protection of ductile iron pipe is a controversial
subject. Because of this, it was generally agreed that Reclamation had little choice other than to
carefully consider past experience and establish a conservative guideline that they will
consistently follow. ”
Reclamation Response: Discussions in Section 6.1 of the Technical Memorandum, as
well as the revisions to the Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s updated position
concerning the use of polyethylene encasement.
Panel Comment 7. “There was no disagreement concerning the first recommendation, use
polyethylene encasement as per revised (2004) Table 1, presented for the Questions session with
the panel. This appears to be a reasonable technical position, based on available knowledge and
their past experience.”
Reclamation Response: Discussions in Section 6.1 of the Technical Memorandum, as
well as the revisions to the Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s updated position
concerning the use of polyethylene encasement.
Panel Comment 8. “The topics targeted for research in the recommendations were agreed to
include the important and pressing issues.”
Reclamation Response: The recommendations in the Technical Memorandum have
incorporated additional research performed since the completion
of the draft report. Reclamation will weigh the need for further
research on this issue against other research needs of the agency.

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Appendix A
Responses to Review Panel Input

Reclamation’s Responses to Specific Comments and
Recommendations on the Draft Report Made by the Review Panel
The Review Panel’s comments, discussions, and recommendations were considered and
incorporated into the body of the Technical Memorandum, including the revised Corrosion
Prevention Criteria and Requirements Table (table 2), where deemed appropriate. Applicable
portions of the draft report, “Corrosion Considerations for Ductile Iron Pipe,” as well as
information addressing the Review Panel’s comments, were included in the body of the
Technical Memorandum rather than finalizing the draft report.
Listed below are specific comments on the draft report from the Review Panel, followed by
Reclamation’s responses:
Panel Comment: “The original title of this draft report, as prepared by Tom Johnson (formerly
Reclamation’s corrosion engineer), was “Corrosion Considerations for Ductile Iron Pipe.”
(Appendix B, title page).
Reclamation Response: Portions of the draft report, as well as information addressing
the Review Panel’s comments, were included in the body of the
Technical Memorandum rather than finalizing the draft report.
Panel Comment: “Was cathodic protection required also? If not, why not? If so, state it.”
(Appendix B, page B-1).
Reclamation Response: Requirements for cathodic protection would have been based on
soil resistivities.
Panel Comment: “What was the reason for the change?” (Appendix B, page B-1).
Reclamation Response: The background for changes to the Corrosion Prevention
Criteria and Requirements Table are discussed in Section 2.1 of
the Technical Memorandum.
Panel Comment: “Why not electrically isolate the areas that need CP and not have to CP the
entire length? In many cases, we have been able to segment alignments, provide CP where
necessary and not burden the project with unnecessary corrosion requirements.” (Appendix B,
page B-2).
Reclamation Response: This is a design approach that should be considered for each
project on a case-by-case basis.

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Appendix A
Responses to Review Panel Input

Panel Comment: “Either here or later on, there should be some mention of the other factors and
issues related to corrosivity discussed by AWWA C105 or DIPRA…while resistivity is a major
factor, there are other factors.” (Appendix B, page B-2).
Reclamation Response: Additional factors related to corrosivity are discussed in
Section 6 of the Technical Memorandum.
Panel Comment: “Does Reclamation assume or require electrical isolation from appurtenances
and other external factors?” (Appendix B, page B-2).
Reclamation Response: Reclamation requires electrical isolation from appurtenances,
structures, and between differing pipe types.
Panel Comment: “If to date there has not been a reported corrosion failure of any ductile iron
pipeline on a Reclamation-designed project or on a project for which Reclamation has had an
oversight responsibility, then what is the concern for corrosion damage? Something needs to be
described here for justification for the concern. ” (Appendix B, page B-2).
Reclamation Response: Reclamation periodically reviews its design standards and
criteria to reflect recent agency and industry experience. This
review was prompted by concerns within the pipe and corrosion
industries regarding the effectiveness of polyethylene
encasement.
Panel Comment: “It is my belief and practice that making pipelines electrically continuous is
simply a matter of preserving options in the future. From a stray current standpoint, by making
pipelines electrically continuous more stray current is collected, but only electrically continuous
pipelines can be monitored for stray current and when identified, can be effectively mitigated
using standard pipeline methods. Further, the application of cathodic protection at any time is
simplified. Pipelines should be made intentionally electrically continuous using appropriately
sized joint bonds as a matter of general practice.” (Appendix B, page B-4).
Reclamation Response: Discussions concerning electrical continuity are included in
Section 3.4.5 of the Technical Memorandum.
Panel Comment: “What about the use of clean sand backfill?” (Appendix B, page B-4).
Reclamation Response: The importance of backfill is discussed in several locations in
the Technical Memorandum, including Sections 4.1.1 and 6.1.
Panel Comment: “You should discuss the 10 point system, its components and merits.”
(Appendix B, page B-5).
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Appendix A
Responses to Review Panel Input

Reclamation Response: The 10 point system is discussed in Section 3.3 of the Technical
Memorandum.
Panel Comment: “The 49 CFR 192 and 195 regulations are for oil and gas, it does not mean
they are applicable. There are lots of other requirements in the CFRs that are also not followed
in the water industry. Unless you are willing to accept the entirety of the requirements, you
might want to tone down the use of these CFRs.” (Appendix B, page B-6).
Reclamation Response: Section 4.1.1 of the Technical Memorandum states that these
two documents were primarily developed for the oil and gas
industry, but that the information contained in them is relevant
to the discussion in that section.
Panel Comment: “Based on the cost of cathodic protection, you can show that from an
economic standpoint you should never pay more than $3 per square foot for a coating because
you can cathodically protect it for that amount. Reference: G.E.C. Bell, Value Engineering
and Corrosion Control, AWWA Cal-Nevada Section, Spring Meeting, April 10, 1997,
San Jose, CA. ” (Appendix B, page B-8).
Reclamation Response: This subject is discussed in Section 6.1 of the Technical
Memorandum.
Panel Comment: “Suggest considering the positions of the Europeans and other international
groups on the issue. He states that it is his understanding that polyethylene encasement has not
been accepted as the sole form of protection for ductile iron in Europe. Also consider noting that
in the U.S., the situation with respect to polyethylene encasement seems to have resulted in the
evolution of 3 camps: (1) those outright rejecting polyethylene encasement and treating of
ductile iron pipe the same as steel pipe, (2) those completely accepting polyethylene encasement,
and (3) those somewhere between these two positions. This would seem to reinforce the
conservative position recommended by Reclamation, namely, limiting the use of polyethylene
encasement until research answers the fundamental questions posed in the Recommendations
section. ” (Appendix B, page B-11).
Reclamation Response: European practices are discussed in Section 4.1, and listed in
table 7 of the Technical Memorandum. Discussions in Section
6.1 of the Technical Memorandum, as well as the revisions to
the Corrosion Prevention Criteria and Requirements Table,
reflect Reclamation’s updated position concerning the use of
polyethylene encasement.

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Appendix A
Responses to Review Panel Input

Reclamation’s Responses to the Panel’s Conclusions on
Six Questions Regarding Corrosion Protection Practices
Questions for the Panel and Panel Conclusions
1. Reclamation currently requires protection on pipe alternatives (i.e., no bare pipe is
installed) should problems be encountered in the future due to either environmental
corrosion or stray current.
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?
Jackson – Concurred
Bell – Concurred, but noted that cost is a consideration. He said coatings should be
used for costs up to $3/ft2 , because cathodic protection can be applied for
about this cost.
Reclamation Response: A discussion of this topic is included in
Section 6.1 of the Technical Memorandum.
Cheng – Concurred

2. Reclamation currently requires bonded joints and Corrosion Monitoring for all
pipeline installations in order to monitor and assess pipe corrosion activity.*
*Note: With the exception of reinforced concrete pipe without steel joint rings. (See
section 5.0 for discussion.)
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?
Jackson – Concurred; but said one should allow for exceptions.
He said that in special cases where there are stray currents one should
consider isolation rather than conductivity. For example, he worked on a
project where a pipeline paralleled a high voltage power line. In that
situation, isolation from other structures is definitely needed, and can be
achieved by reducing the continuous length of pipe that can draw a stray
current.

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Appendix A
Responses to Review Panel Input

Reclamation Response: This is a design approach that should be
considered for each project on a case-bycase basis.
Bell – Concurred that bonded joints and test stations are needed, and that isolation
from other structures is important. He also stated that with a bonded coating,
one may not be able to see changes in the potentials on the pipeline, meaning
it may be difficult to detect if corrosion is occurring. He felt that newer
technologies, such as electrical resistance coupons, may be better.
Reclamation Response: This is a design approach that should be
considered for each project on a case-by-case
basis. Reclamation’s position has been and
continues to be that all buried metallic
pipelines be installed with corrosion
monitoring systems, with the exception of
reinforced concrete pipe without steel joint
rings. (See section 5.0 for discussion.)
Cheng – Concurred with the practice of corrosion monitoring. He also stated that
one needs to monitor for unusual circumstances and changes in potential,
and have a practice or written guideline to establish what changes to look
for and what to do if changes are found.
Other comments:
Connections from sublaterals to main pipeline account for 90 percent of all
corrosion problems on distribution systems. Isolation is the key.
Reclamation Response: Reclamation requires electrical isolation from
appurtenances, structures, and between
differing pipe types.
Cathodic protection is the last resort if there are problems.
Reclamation Response: We agree that installation of a corrosion
monitoring system allows for testing and
determination of precise requirements for
implementation of a cathodic protection
system, if necessary.

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Appendix A
Responses to Review Panel Input

3. Reclamation currently uses soil resistivity and stray current as an indicator of need for
CP. Additionally, in some cases Reclamation will examine chlorides and sulfates
concentrations in the soil. This approach does not consider, or may be considered to
assume, other parameters of soil chemistry, pH, Oxidation Reduction Potential (Redox),
cyclic wetting and drying (moisture), etc. This parameter is quick, easy and cheap to
measure in the field.
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?
Jackson – He stated that field resistivity is one part of the data gathering. CH2M
Hill prefers the collection of additional information for major pipelines,
e.g., pH, chlorides, and sulfates. Resistivity values are calculated in the
laboratory (saturated) as well as in the field. He stated that the potential
for stray currents needed to be evaluated, and that a conservative
assumption would be that every project is likely to have stray current.
The use of PE encasement to provide shielding from stray currents is a
good idea.
Reclamation Response: This is a design approach that should
be considered for each project on a
case-by-case basis. Section 6.1 of the
Technical Memorandum discusses the
importance of evaluation of a variety of
factors that could influence corrosion.
Bell – He felt the best approach was to get the pipe in the ground and then determine
what is needed. He stated that even hazardous pipelines are given 1 year of
operation to allow for tweaking of CP to meet exact needs of a particular
pipeline.
Reclamation Response: Discussions in Section 6.1 of the Technical
Memorand um, as well as the revisions to
the Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s
updated position concerning corrosion
provisions. Reclamation concurs that initial
operation of a CP system should be reviewed
and adjusted as necessary.
He stated that resistivity is a good indicator of corrosion mitigation needs, but
that the use of Electro-Magnetic Conductivity Surveys may be better.
Measurements could be taken every 20 feet to 15 feet of depth. This method
should be used to find where there are changes, and that data should be used
A–9

Appendix A
Responses to Review Panel Input

to determine the field sampling locations. He stated that the anions–chlorides
and sulfides—as well as the cations—calcium, magnesium, and sodium need
to be measured. He felt that there is a small price difference between a full
analysis and a partial analysis, and that this extra analysis helps determine
where to put magnesium beds.
Reclamation Response: This is a design approach that should be
considered for each project on a case-by-case
basis.
Other comments:
Bell – A conservative assumption would be to use good coatings and CP for lower
resistivity soils.
Reclamation Response: Discussions in Section 6.1 of the Technical
Memorandum, as well as the revisions to the
Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s
updated position concerning corrosion
provisions.
Bell – Stray current is difficult to assess. The conservative view is to assume
projects are likely to have future potential for stray current.
Reclamation Response: This is a design approach that should be
considered for each project on a case-by-case
basis.

4. PE effectiveness is a disputed issue both for its ability to protect pipe from corrosion,
possible installation damage and potential shielding which impacts Corrosion
Monitoring and CP. For example, NACE International’s RPO 169-2002 “Control of
External Corrosion on Underground or Submerged Metallic Piping Systems,” requires
a bonded dielectric coating for buried pipeline applications and indicates that
unbonded coatings (PE encasement is considered an unbonded coating) can create
electrical shielding of the pipeline that could jeopardize the effectiveness of the CP
system. Reclamation is concerned by this dispute.
Does the panel have comments with regard to the effectiveness of PE encaseme nt as
a corrosion measure and/or its effect on the ability to monitor pipe corrosion and to
apply effective CP?

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Appendix A
Responses to Review Panel Input

Jackson – He felt that PE encasement is not a perfect answer, but there are locations
in less corrosive environments where it can be used. He agreed that
Reclamation has a legitimate concern and needs to take a conservative
view, and should make changes to corrosion mitigation criteria if
warranted.
Reclamation Response: This is a design approach that should be
considered for each project on a case-bycase basis. Discussions in Section 6.1 of
the Technical Memorandum, as well as the
revisions to the Corrosion Prevention
Criteria and Requirements Table, reflect
Reclamation’s updated position
concerning corrosion provisions.
Reclamation’s corrosion provisions
indicate agreement with Mr. Jackson’s
statement that PE encasement can be
used in locations with less corrosive
environments.
Jackson – He has used PE encasement with CP, and has not had any cases where he
has been called to go back and inspect the pipe. This would indicate that
there have been no specific problems for these cases.
Jackson – He said that two other aspects should be considered:
1. As the pressure class decreases, the pipe thickness decreases,
making the thinner pipe more susceptible to penetration. The
pipe thickness also decreases as the size decreases.
2. Bedding and backfill are critical and must be considered
carefully. CH2M Hill likes to use sand as a bedding material
for DIP with PE. A minus ¼” gravel may be reasonable. Digups have shown damage to the PE, especially around the top of
the pipe. Two layers of PE encasement could help eliminate
this problem.
Reclamation Response: The importance of backfill is
discussed in several locations in the
Technical Memorandum, including
Sections 4.1.1 and 6.1.
Jackson – CH2M Hill is more conservative with larger diameter pipe because the
flows are larger, the implications of the failure are greater, and large
A – 11

Appendix A
Responses to Review Panel Input

diameters are more expensive to fix. With larger pipe, a more
conservative approach is warranted. With 12- inch and smaller pipe, less
conservatism may be needed.
Reclamation Response: Discussions in Section 6.1 of the Technical
Memorandum, as well as the revisions to
the Corrosion Prevention Criteria and
Requirements Table, reflect Reclamatio n’s
updated position concerning corrosion
provisions.
Bell – He stated that he leans towards the use of PE encasement with CP applied,
because he has seen it work. He agreed that PE encasement cannot be
considered to be a coating; it is an encasement only. He said that data has
recently been published which indicates DIP with a select backfill can be
protected with PE encasement to reduce corrosion, and that CP works under
intact PE.
He noted that RP0169 (RP stands for Recommended Practice) recommends a
tight bonded coating, but that it is not a requirement; it is only a
recommended practice. He stated that he has never specified tight bonded
coating with DIP.
He stated that he has had good experience with PE encasement and with the
application of CP on polyethylene encased DIP. He stated that the costs of
PE encasement are on the order of $0.05/diameter inch of pipe. He also
stated that the cost of CP for DIP with PE encasement can be considered to be
28 times that of steel, but that it is still a small number when put in context of
the entire project cost.
He advised Reclamation to look at its own experience. He stated that if
Reclamation has not had failures with PE encasement, then it should keep
doing what has been done. He said that he has never seen significant failures
of DIP protected with PE encasement and CP.
He said that damage to the PE encasement is not due to the weight or size of
the pipe, but the fact that the wrong type of PE encasement is used. He stated
that the quality of PE encasement can vary greatly, and that lower- quality PE
may not have enough thickness or tensile strength.
He felt that the size restriction on pipe with PE encasement should be
eliminated. He agreed that the consequences of failure need to be considered.
Larger diameter pipe generally does have higher consequences.
A – 12

Appendix A
Responses to Review Panel Input

Reclamation Response: Discussions in Section 6.1 of the Technical
Memorandum, as well as the revisions to the
Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s
current position concerning corrosion
provisions.
Bell – He stated that the fittings on the pipe cause the most problems, because the
pipe is manufactured in a controlled environment, whereas the fittings are a
field installation and not controlled as well. He felt that close inspection
during installation is the best investment.
Reclamation Response: Reclamation has inspectors in the field during
construction.
Bell – Other comments:
The quality of the PE is important.
Inspections and cathodic system maintenance are important.
Reclamation Response: Reclamation routinely performs inspections
and maintenance on its facilities and
encourages the operators of the systems we
build to do the same.
5. Reclamation is prepared to recommend an updated approach for pipe alternative
coatings or encasements installed in various soil conditions. The newest
recommendation is enclosed as Table 2.
Does the Panel concur with the Table?
Does the panel have comments with regard to the Table?
Bell – He stated that a bonded dielectric coating is more difficult to apply and more
expensive for DIP than for steel pipe. With DIP, a thicker coating is needed
due to the dimpling on the pipe, and that the larger the diameter, the greater
the coating thickness becomes. Thick coatings can cause problems at the
joints, making the pipe hard to assemble. Mortar and reinforced concrete
need to be handled differently. Mortar coating in conditions with chlorides
and sulfides is a problem. In wetting and drying conditions, the mortar can
act like a sponge, and eventually lead to chlorides accumulating on the metal.
Corrosion protection additives can be put into the coating. If coal tar epoxy is
used, it should be used directly on the steel, with mortar on the outside for
A – 13

Appendix A
Responses to Review Panel Input

rock protection. He stated that three layers of tape with mortar coating are
pretty much bullet proof. He said that a seal coat over mortar is not a good
system, because it could cause shielding of CP and allow corrosion to occur
under any disbonded mortar coating. The mortar should be used over the
dielectric coating.
Reclamation Response: Discussions in Section 6.1 of the Technical
Memorand um, as well as the revisions to
the Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s
updated position concerning corrosion
provisions.
Bell – He said that both coal tar epoxy and PE encasement can shield CP.
He said that for soil resistivities below 1,500 Ohm-cm, PE encasement with
CP should be used.
He stated that the Reclamation table is geared towards conservatism, and that
this makes sense if it agrees with a good history of installation.
Reclamation Response: Discussions in Section 6.1 of the Technical
Memorand um, as well as the revisions to
the Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s
updated position concerning corrosion
provisions.
Bell – He stated that if CP systems are not always well maintained, one should never
depend totally on CP to protect a pipeline.
Reclamation Response: Reclamation routinely performs inspections
and maintenance on its facilities and
encourages the operators of the systems we
build to do the same.
Jackson – He stated that if a bonded dielectric coating is required, alternatives will
probably be more limited, because pipe will probably not be obtainable
from DIP manufacturers. He said that it is a good idea to make sure there
is more than one pipe alternative available in order to keep capital costs
down.

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Appendix A
Responses to Review Panel Input

Reclamation Response: To the extent practical, Reclamation
includes all technically viable pipe options
in its specifications.
Jackson – He felt that there could be problems with corrosion in any soils with
resistivities below 3,000 Ohm-cm. For resistivities below 2,000, he felt
that corrosion protection designs should definitely be considered. For
resistivities below 1,000, he felt that there could be really serious
problems.
Reclamation Response: Discussions in Section 6.1 of the Technical
Memorandum, as well as the revisions to
the Corrosion Prevention Criteria and
Requirements Table, reflect Reclamation’s
updated position concerning corrosion
provisions.
Jackson – In the end, he felt that the user should adhere to the criteria with which
they are the most comfortable.
Reclamation Response: The design approach for each project
should be determined on a case-by-case
basis.
Other comments:
Bell – Coal tar epoxy can be placed directly on the pipe with mortar over the epoxy
for rock protection.
If the coal tar epoxy is on the outside of the mortar and the mortar becomes
disbonded from the pipe, salty water can be a problem.
Reclamation Response: This is a design consideration that should be
addressed on a case-by-case basis.
6. Pipe life cycle costs, or other economic considerations are important in the overall
design and O&M budgeting and expenditures over the life of a project. Reclamation is
prepared to use pipe life cycle costs as a bid correction item.
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?

A – 15

Appendix A
Responses to Review Panel Input

Jackson – In general, he felt that life cycle costs are needed in specifications. He
concurred with using bid adjustments in specifications for increased costs
due to CP. As an example, CH2M Hill did use long-term costs for the
Mni Wiconi Project, but it did not change the pipe option selected for the
project. The lowest life cycle costs were for DIP with PE encasement and
CP.
Reclamation Response: Life cycle costs are discussed in
Section 4.6 of the Technical
Memorandum.
Bell – He said he has never used life cycle costs, but he would have no problem with
including it. He stated that it would be important to be definitive about how
the calculation will be made.
He said that, in general, the cost of installation of CP is about $2,000 to
$3,000 per installed amp. The current required for ductile iron is about
28 to 30 times that required for steel.
Reclamation Response: Life cycle costs are discussed in Section 4.6
of the Technical Memorandum.
He felt that the average service life for a pipe project should be assumed to be
40-60 years, so a good starting point would be 50 years. He has known
clients that have asked for as high as 100 years.
Reclamation Response: Service life for pipe projects is discussed in
Section 4.5 of the Technical Memorandum.

A – 16

Appendix B
“Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Appendix B
“Considerations in Using Polyethylene Encasement
with Ductile Iron Pipe”
The Review Panel was asked to review a February 12, 2004, draft report prepared by
Tom Johnson (formerly Reclamation’s corrosion engineer). The title of the draft report was
“Corrosion Considerations for Ductile Iron Pipe.” The Panel’s comments are included in the
right margin of the draft report. The Panel’s recommended additions are underlined, and their
recommended deletions are shown as strikeout.

Summary of the Discussions by the Review Panel of the
Draft Document
1. All of the specific additions suggested for the draft by the reviewers were agreed to be
relevant and were incorporated into the draft in one form or another.
2. Although the draft was considered in detail and specific additions and changes were
made, it is premature to consider that full consensus was reached concerning the specific
language in the draft. (The reviewers did not see the final changes to the draft; there was
not enough time to discuss all the details at the panel meeting).
3. There was general consensus that the technical details considered in the existing draft are
reasonable and appropriate, but the scope of the document needed to be more clearly
defined and followed. The draft primarily takes a material (iron versus steel technology)
view of corrosion on ductile iron pipe and is virtually silent on other design aspects that
can influence the corrosion of these materials (such as back fill).
4. Many of the specific comments have been incorporated. It was agreed that this draft
needed significant expansion to cover the scope implied by the title. As the scope and
text stand, it was estimated that the document was between 50 and 70 percent ready for
submittal to a peer-reviewed journal.
5. Either the scope of the document (and title) needs to be clearly defined and limited, to
better reflect the issues actually discussed in the document, or most of the comments in
the draft should be developed and incorporated into the document to better address the
various issues that are not covered in the current draft of “Corrosion Considerations for
Ductile Iron Pipe”.

Appendix B
“Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

6. There was no disagreement on the first conclusion of the document, that the use of
polyethylene encasement for corrosion protection of ductile iron pipe is a controversial
subject. Because of this, it was generally agreed that Reclamation had little choice other
than to carefully consider past experience and establish a conservative guideline that they
will consistently follow.
7. There was no disagreement concerning the first recommendation, use polyethylene
encasement as per revised (2004) Table 1, presented for the Questions session with the
panel. This appears to be a reasonable technical position, based on available knowledge
and their past experience.
8. The topics targeted for research in the recommendations were agreed to include the
important and pressing issues.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

MERL-2004-01

Corrosion Considerations for Ductile Iron Pipe
Considerations in using Polyethylene Encasement with Ductile- Iron
Pipe

The Review Panel was asked to review a February 12,
2004, draft report prepared by Tom Johnson (formerly
Reclamation’s corrosion engineer). The title of the
draft report was “Corrosion Considerations for Ductile
Iron Pipe.” The Panel’s comments are included in the
right margin of the draft report. The Panel’s
recommended additions are underlined, and their
recommended deletions are shown as strikeout.

D. Thomas Johnson
U.S. Department of Interior
Bureau of Reclamation
Denver Technical Service Center
Materials Engineering and Research Laboratory
With Panel Peer Review and Comments
February 12, 2004
April 2004

Comment [SL1]: The original title of this draft
report, as prepared by Tom Johnson (formerly
Reclamation’s corrosion engineer), was “Corrosion
Considerations for Ductile Iron Pipe”

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Contents
Page
Introduction ................................................................................................................................... B-1
Background ................................................................................................................................... B-1
Corrosion of Ductile Iron Pipe...................................................................................................... B-2
Corrosion Mitigation Methods Typically Used for Ductile Iron Pipe .......................................... B-5
Polyethylene Encasement .................................................................................................... B-5
Bonded Dielectric Coatings ................................................................................................. B-7
Discussion ..................................................................................................................................... B-8
Corrosion Monitoring Systems ............................................................................................ B-8
Protective Coatings .............................................................................................................. B-9
Polyethylene Encasement .................................................................................................... B-9
Conclusions and Recommendations ........................................................................................... B-12
Cited References ......................................................................................................................... B-14
General References ..................................................................................................................... B-18

Table 1

Corrosion Prevention Criteria and Requirements ..................................................... B-25

Figures

...................................................................................................................... follows B-26

Appendix ...................................................................................................................... follows B-32
Corrosion............................................................................................................................ B-33
The Basic Corrosion Cell .......................................................................................... B-33
Factors Influencing Corrosion .................................................................................. B-34
Corrosion Mitigation .......................................................................................................... B-36
Corrosion Monitoring Systems ................................................................................. B-36
Protective Coatings ................................................................................................... B-36
Cathodic Protection ................................................................................................... B-37
Synergistic Effects of Protective Coatings and Cathodic Protection ........................ B-38

B–i

Comment [BOR2]: Note that this document was
converted to Word 2007 in Feburary 2010. Redline
and strikeouts have been re-done to match the
original publication.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Corrosion Considerations for Ductile Iron Pipe
Introduction
Because of corrosion concerns recently raised relative to raised regarding the use of cathodically
protected, polyethylene encased, ductile iron pipe Reclamation has initiated a study to evaluate
the corrosion mitigation alternatives listed in the table titled Corrosion Prevention Criteria and
Requirements (See Table 1). The original study was to take approximately 18 months with a
completion date of December 2004 and was to include all pipe options used by Reclamation. As
a result of the language within Reclamation’s 2004 Budget with its accompanying March 2004
deadline, the original study was modified such that the ductile iron pipe alternative would be
evaluated first. Therefore, this report concentrates on the corrosion control considerations of
ductile iron pipe. Corrosion considerations for ductile iron pipe are reviewed and
recommendations are given for Reclamation positions on the criteria listed in Table 1 for ductile
iron pipe.

Comment [m3]: Who? Based on what?

This report is based on Reclamation's experience, the experience of other professionals in the
corrosion and water industries, a review of pertinent national standards, recommended practices,
and a review of relevant literature.
As the study progressed it became apparent that significant technical issues remain regarding
corrosion mitigation control methods for ductile iron pipe and, therefore, an economic analysis
of the corrosion mitigation alternatives for ductile iron pipe was not performed. However,
economic considerations are relevant to pipeline design and material selection. The two
corrosion prevention methods listed in Table 1 for ductile iron pipe will have different costs for
design, construction, and normal O&M, and the effectiveness of the selected corrosion
prevention method will have future economic consequences (i.e. leak repair cost, property
damage, and pipeline service life). There are some quantitative data on the failure rates of both
methods, but the uncertainty of the data precludes a definitive life cycle cost analysis for
deciding between the two methods. Therefore, selection of the form of the protection should be
based on the technical merits and weaknesses of each method.
Comment [gecb4]: Was cathodic protection
required also? If not why not? If so state it.

Background
The Bureau of Reclamation first considered using ductile iron pipe on projects in the mid 1960’s.
At that time Reclamation’s position was that from a corrosion standpoint ductile iron pipe would
be treated as steel pipe and coated with a bonded dielectric coating. In the late 1970’s
Reclamation added polyethylene encasement as an alternative corrosion mitigation method for
ductile iron pipe. In the early 1990’s Reclamation placed a restriction on the pipe weight and
diameter for which polyethylene encasement could be used and, as such, polyethylene
encasement currently is applicable only for smaller and lighter ductile iron pipe. Currently
within Reclamation, ductile iron pipe can be installed with either polyethylene encasement (for
smaller and lighter pipe) or a bonded dielectric coating (for all pipe sizes), and cathodic
protection may be used with both coatings..

B–1

Comment [gecb5]: What was the reason for the
change?
Comment [gecb6]: Again, what was the reason
for the change?
Comment [gecb7]: Was weight used as a means
of limiting pressure ranges and therefore pipe
thickness?
Comment [gecb8]: 24-inch diameter??
Comment [dh9]: Need to name the particular
reference standard that you used “RP o169 NACE
Comment [gecb10]: What are the design
criteria for cathodic protection? Does Reclamation
require -850 mv to SCE for both pipes? Has there
ever been a failure on a cathodically protected
polyethylene encased pipe? How about
dielectrically coated steel pipe with CP?

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Within Reclamation the decision to use cathodic protection on buried pipelines is based on soil
resistivity, but all buried metallic pipelines receive corrosion monitoring systems as a minimum.
Pipelines traversing lower resistivity soils, measured by field tests and data interpretation
according to Reclamation standards, require cathodic protection. The corrosion prevention
criteria and requirements (Table 1) are guidelines used by Reclamation when making corrosion
prevention recommendations for buried line pipe alternatives. It should be noted that other
parameters such as performance history and stray current exposure for a given route, criticality
of the structure, conservatism employed in the design, and specific client requests should be
considered when determining corrosion prevention requirements for a specific pipeline. In
addition, the specified corrosion prevention requirements for a particular pipeline should be
developed by a corrosion engineer working directly with the pipeline designer. The guidelines
are not intended to be rigid in use but used as a tool in formulating the corrosion protection
scheme on a particular pipeline.
Currently within Reclamation cathodic protection is recommended (depending on soil resistivity)
on ductile iron pipe with either a bonded dielectric coating or a polyethylene encasement.
Overall Reclamation’s use of ductile iron pipe is somewhat limited as a line pipe alternative. To
the best of the author’s knowledge, Reclamation has been involved with installation of over 330
miles of ductile iron pipe. Approximately 30 miles of ductile iron pipe has been installed on
Reclamation designed projects. The ductile iron pipelines on Reclamation designed projects
were installed beginning in the late 1970’s and are 24 inches in diameter or less. Additionally,
over 300 miles of ductile iron pipe has been installed on non-Reclamation projects where
Reclamation has had oversight responsibilities (the projects were not designed by Reclamation).
Ductile iron pipelines installed with Reclamation oversight typically have been installed with
polyethylene encasement and cathodic protection. To date there has not been a reported
corrosion failure of any ductile iron pipeline on a Reclamation designed project or on a project
for which Reclamation has had an oversight responsibility.
Appendix A for this report contains fundamental concepts relative to corrosion and corrosion
mitigation. This report assumes that the reader has some understanding of the fundamental
concepts and, therefore, all readers are encouraged to review these fundamental concepts.
Corrosion of Ductile Iron Pipe
The corrosion experienced on by buried metallic structures is more dependent on the
environmental characteristics than the compositional variations within a specific type of material
(Romanoff, 1957). It is widely generally accepted that steel, cast iron, and ductile iron steel and
iron pipe materials corrode at similar rates in similar soils (Kroon, 2004; FHWA, 2001;
Fitzgerald, 1968; Romanoff, 1968).
Both cast iron and ductile iron contain free carbon in the form of graphite (Anver, 1974). The
graphite in gray cast iron is in the form of flakes, where as, in ductile iron it is in the nodular or
spheroidal form. The different differing forms of graphite in gray cast iron and ductile iron have
resulted result in differences of mechanical properties, with ductile iron having the properties.
Ductile iron has greater ductility and tensile strength. However, the different forms of graphite
B–2

Comment [m11]: Why not electrically isolate
the area that need CP and not have to CP the entire
length? In many cases, we have been able to
segment alignments, provide CP where necessary
and not burden the project with unnecessary
corrosion requirements.
Comment [m12]: What is methodology
(sampling) for the 10% probability determination?
Weibull (sp) plots per mile or 1000 meters? Are the
tests field or laboratory tests? If laboratory tests,
what is the moisture content? What is the interval of
testing? Are all of the tests from pipe depth?
Comment [m13]: Either here or later on, there
should be some mention of the other factors and
issues related to corrosivity discussed by AWWA
C105 or DIPRA…while resistivity is a major factor,
there are other factors. The reality is that the
Reclamation limits on resistivity are such that for
virtually every pipeline, coatings or encasement and
CP will be required for both steel and DIP.
Comment [m14]: Don’t you really mean the
Risk of Failure (Probability of Corrosion Failure X
Consequence of Failure)?
Comment [m15]: Does Reclamation assume or
require electrical isolation from appurtenances and
other external factors? I have found that isolation
from external galvanic cells is more important than
soil corrosivity.
Comment [m16]: Need to state how many total
miles of pipe Reclamation has been involved in the
installation of during the same period.
Comment [m17]: Design, construction, what
was the role of Reclamation?
Comment [m18]: if to date there has not been a
reported corrosion failure of any ductile iron pipeline
on a Reclamation designed project or on a project for
which Reclamation has had an oversight
responsibility. Then what is the concern for
corrosion damage? Something needs to be described
here for justification for the concern. I thought the
materials on page 8 under Discussion touch this
issue, but they need to be expanded and moved up
here. Although no failures have been reported,
failures in other areas have been cited. So, there are
possibilities that corrosion of ductile iron pipes with
BOR’s designs or under BOR’s oversight might
occur. It also might be important to state that the cost
of a failure will be enormous. Along the same line,
it is worthwhile to estimate the failure probability of
ductile iron pipes due to corrosion. This is might be
complicated due to many factors involved, such as
the pipe dimension, soil properties and environment,
etc. But it can be done on assumed realistic
conditions.
... [1]
Comment [m19]: If there is only one appendix,
A is not needed.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

have not resulted in differences in their corrosion characteristics higher strength than cast iron.
However, the corrosion rates of cast and ductile iron are not significantly different (Makar et al.,
2002; Romanoff, 1968).
Although they corrode at approximately ductile/cast iron and steel corrode at nominally the same
rate there is a very important difference between the corrosion characteristics of steel and that of
cast iron or ductile iron. Cast and ductile iron pipe typically corrode by graphitization or pitting.
Graphitization does not occur with steel, which typically corrodes by pitting. Graphitic
corrosion is a type of dealloying process in which the iron rich matrix within the iron/carbon
matrix of cast and ductile iron is surrounding the graphite (carbon) preferentially corroded
corrodes due to the galvanic couple between the iron and graphite. Iron is anodic to graphite and
when galvanically coupled electrically-coupled in contact with an electrolyte with graphite the
iron will experience accelerated corrosion. As the iron corrodes, corrode at an accelerated
corrosion rate. As the iron rich regions corrode, it is replaced by a porous the iron/carbon matrix
transforms to a porous iron oxide/carbon marix with an accompanying iron oxide corrosion
product and this change in the microstructure is accompanied by a reduction of mechanical
properties (e.g., density, ductility and tensile strength). The graphitized material tightly adheres
to the metal substrate. There is generally no visible evidence of graphitic corrosion; the original
pipe surface remains the same including contour, texture, and color (there may be a very slight
color change). Pitting corrosion is usually easily identified and is visually evident by surface
cavities and/or color variation due to the presence of corrosion products. In either case,
graphitization or pitting, the end result is the same; there is a cavity in the pipe wall.
Experience indicates that it is prudent to account for corrosion, especially when metal pipe is
buried. The practice of adding extra wall thickness as a means of extending service life for
corrosion that occurs over time has been used historically and is employed today in some cases.
However, the use of an effective corrosion protection system allows the most economical use of
pipe material because excessive wall thickness is not required. The wall thickness of gray cast
iron was gradually reduced as manufacturing techniques improved and alloys became stronger
and more consistent, and this trend has continued with ductile iron. Modern ductile iron pipe can
have substantially thinner walls than comparable old cast iron pipe for the same pressure service.
However, corrosion rates haven’t changed, so thinner walls make corrosion control a more
important consideration for ductile iron pipe.
Figures 1 and 2 are of a gray cast iron pipe removed from a pipeline, which was approximately
60 years old. This specific pipe section had not failed in service although the pipeline was
replaced due to repeated failures. Prior to sand blasting it It was evident in initial inspections
that the pipe section had experienced graphitic corrosion, (evident by scraping away the outer
pipe wall with a knife) although the extent of corrosion was not apparent. After sand blasting,
which removed only the porous carbon/corroded iron regions of the pipe, it was readily apparent
that a large percent of the surface experienced corrosion and at three locations the pipe wall was
completely perforated due to graphitic corrosion.
Because of the tightly adhering nature of graphitic corrosion products, graphitized pipe is
capable of containing withstanding significant pressure even when corrosion has fully penetrated
perforated the pipe wall (Romanoff, 1957; Smith, 1963). Although this is a desirable property it
B–3

Comment [m20]: What is the reference for this?
In general, I find that there is a change in surface
condition, in particular the soil in the area of the
graphitization is tightly adhered and that there is a
smoothing of the surface.
Comment [m21]: It would be recommended that
a brief discussion of localized versus general
corrosion be included here. You may want to
include this in the appendix that gives the primer on
corrosion. The four parts of the corrosion cell are all
the same, only the length scale is different. This is
important because general corrosion is not as
important as pitting because for a pipeline, a single
perforation constitutes a failure.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

can not property, it cannot be relied upon as an engineering property. The brittle nature of low
toughness of the graphitic corrosion products result in the graphitized pipe being susceptible to
failures from stress caused by such factors as surges, freeze/thaw, expansive soils, temperature
changes, and vehicular loading.
It is recognized within the corrosion industry that graphitic corrosion is not easily identifiable
and as a result it is believed that many failures of gray cast iron and ductile iron pipes are not
identified as corrosion related, where as, however, the root cause of the failure may indeed be
due to corrosion (Romanoff, 1968; Fitzgerald, 1968; Gummow, 1978; Chambers, 1983;
CANMET, 1983; Jakobs and Hewes, 1987, 1987; Makar et al., 2000). This recognition, along
with the recognition of corrosion and corrosion mitigation in general, has not been widely
transferred to the water industry (Fitzgerald, 1968; FHWA, 2001; Spicklemire, 2002). As a
result, the actual number of corrosion related failures of gray cast iron and ductile iron pipes are
likely higher than the statistics indicate (CANMET 1983; Jakobs and Hewes, 1987; Szeliga and
Simpson, 2003). Canadian studies investigating water main failures indicate that corrosion is a
primary cause in the majority of water main failures (Chambers, 1983; CANMET, 1983; Jakobs
and Hewes, 1987; Brander 2001). It is interesting to note that because the majority of water
main failures are corrosion related they could have been prevented with theimplementation of
available corrosion mitigation techniques.
Stray current corrosion is should always be a consideration for buried pipelines. Rubber
gasketed, bell and spigot joints are often used on pipelines in the water industry and often can
result in a pipeline which that is not electrically continuous, see Figure 3. Another factor for
corrosion mitigation on ductile iron pipe is the possibility of non-electrically continuous joints.
The electrical continuity across the joint is dependent on theRubber-gasketed joints are
commonly used in ductile iron pipe, so continuity is an issue when stray current is considered.
Electrical continuity may or may not occur depending upon the extent of physical contact
between the bell and spigot. Joint bonds are generally necessary if continuity is to be spigot ends
of a joint. If physical contact exists electrical continuity can occur, although without installation
of electrical continuity joint bonds positive continuity is not obtained. assured. An electrically
discontinuous pipeline collects less stay current than an electrically continuous pipeline which
results in less stray current corrosion (Bonds, 1997). However, any current that is collected on
an electrically discontinuous pipeline can cause stray current corrosion when the current leaves
the pipe surface to get and gets around an the electrically discontinuous pipe joint. Preventing
stray current corrosion usually requires establishing a metallic path (wire) between the affected
piping and a suitable drain point or connection to the source of the current. Bonding the pipe
joints helps ensure that a metallic path is provided from the drain point to all parts of the
pipeline, thereby preventing a corrosive stray current discharge directly from the pipe to the soil.
In summary; summary, steel, cast iron, and ductile iron are capable of corroding corrode when
buried. They corrode at approximately the same rate and the corrosion experienced is highly
damage is dependent on the corrosion characteristics of the soil and/or stray currents. corrosivity
of the soil, the stray currents, and details of the design and construction. In the absence of
protective measures, the time required for corrosion to penetrate the pipe wall is determined by
the severity of the corrosive condition and the wall thickness of the pipe.

B–4

Comment [m22]: These points are generally true
for all metal pipe. The wording should be revised to
make it more readable for the non-specialist.

Comment [m23]: It is my belief and practice that
making pipelines electrically continuous is simply a
matter of preserving options in the future. From a
stray current standpoint, by making pipelines
electrically continuous more stray current is
collected, but only electrically continuous pipelines
can be monitored for stray current and when
identified, can be effectively mitigated using
standard pipeline methods. Further, the application
of cathodic protection at any time is simplified.
Pipelines should be made intentionally electrically
continuous using appropriately sized joint bonds as a
matter of general practice.
Comment [m24]: Continuing with the line of
thinking from above, discontinuous pipe is not an
option because you can not monitor discontinuous
pipelines for stray current.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Corrosion Mitigation Methods Typically Used for Ductile Iron Pipe
Corrosion mitigation methods typically used for ductile iron pipe include polyethylene
encasement, bonded dielectric coatings, select backfill, and/or cathodic protection.

Comment [m25]: What about the use of clean
sand backfill? See below. Add reference here.

Polyethylene Encasement
It has been over 40 years since polyethylene encasement was first used on a buried pipeline. The
use of polyethylene encasement within the water industry has been and still is controversial.
This section will introduce the more prominent issues that are generally presented by the
proponents and opponents of using polyethylene encasement.
Polyethylene encasement is a dielectric coating barrier, which is not bonded to the underlying
metallic surface. Within this report there are two concepts used to identify pipe surfaces in
relation to the polyethylene encasement, which require some explanation. The concepts are pipe
surfaces “opposite “adjacent to holidays in the polyethylene encasement” and “under intact
polyethylene encasement.” As indicated in Appendix A, and shown in Figure 4, a holiday is a
discontinuity in a coating which barrier that exposes the underlying metallic surface directly to
the corrosive environment. The pipe surface opposite a holiday in the polyethylene encasement
refers to the pipe surface which is directly under the holiday. in the vicinity of the holiday to the
environment (electrolyte). The pipe surface under intact polyethylene encasement refers to the
pipe surface directly under polyethylene encasement which that does not contain a holiday at that
specific location; however, holidays in the polyethylene encasement located away from the
specific location of interest may be present.
Proponents of using polyethylene encasement indicate that in most corrosive soils polyethylene
encasement alone is the recommended corrosion mitigation technique (AWWA M41, 2003).
However, in uniquely severe environments other corrosion mitigation techniques, such as tight
bonded coating and/or cathodic protection, should be considered (Stroud, 1989). This also
includes the use of cathodic protection with polyethylene encased ductile iron pipe, where the
polyethylene encasement reduces the amount of current required for cathodic protection current
required (Smith, 1970; Clark, 1972; Stroud, 1989; Schiff and McCollom, Lisk, 1997). American
Water Works Association (AWWA) C105 “Polyethylene Encasement For Ductile-Iron Pipe
Systems” is a national standard which is often referenced as supporting documentation for
polyethylene encasement. The main body of AWWA C105 covers materials and installation
procedures for polyethylene encasement of ductile iron pipe. The thrust of AWWA C105 is
materials and installation, and not under what conditions to use it. Appendix A of C105 gives
conditions for use of PE as well as other corrosion control methods for ductile iron pipe.
Proponents of polyethylene encasement generally agree with the following:
1. The mechanisms of corrosion protection provided by polyethylene encasement are that of
placing a dielectric barrier between the pipe wall and soil, and causing which causes
oxygen starvation within of the corrosion cell.

B–5

Comment [m26]: Suggest using some figures
here. Also suggest mentioning the criteria in C105
for deciding to use polyethylene encasement include
resistivity of 700 ohm-centimeters, which is
suataintially below Reclamation criteria in Table 1.
(The test methods are different (AWWA C105 uses a
soil box versus Reclamation field test) but the
resistivity criteria are still widely different.

Comment [m27]: Actually, C105 Appendix A
gives the 10 point system and suggests that PE
encasement be used when 10 points are required.
You should discuss the 10 point system, its
components and merits at this time. In addition, a
discussion of ASTM A888 used for CIP should be
discussed and cited in this section.
Comment [m28]: Suggest listing reference for
each point, if possible.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

2. Intact Voids in polyethylene generally occur at bell and spigots where the polyethylene
wrap is not necessarily in direct contact with the pipe surface. Polyethylene encasement
acts as a barrier and prevents direct contact between the pipe and soil.
3. The polyethylene encasement is not bonded to the pipe. Therefore, if space exists
between the encasement and the pipe surface and, as such, allows moisture can exist
within the annular space between the pipe and polyethylene encasement. The moisture
Moisture, when present, and its dissolved oxygen will initially result in corrosion on the
pipe surface, but once the dissolved oxygen is consumed by the initial corrosion reaction
further corrosion will be stifled. The moisture devoid of oxygen within the annulus space
then provides a noncorrosive, uniform environment to the pipe surface.
4. The polyethylene encasement retards the transport of dissolved oxygen to and corrosion
products away from the pipe surface.

Comment [m29]: Voids in polyethylene
generally occur at bell and spigots where the
polyethylene wrap is not necessarily in direct contact
with the pipe surface. Add this comment to point 3
of the text, last sentence

5. Significant exchange of moisture within the annulus is prevented by the weight and
compaction of the backfill. backfill, which presses the polyethylene against the pipe.
6. Stray current corrosion from external sources is reduced by the dielectric barrier of the
polyethylene.
7. Although it may be required, polyethylene Polyethylene encased pipe can be cathodically
protected.
Opponents of Opponents of using polyethylene encasement indicate that the pipe surface
opposite surfaces adjacent to holidays in the polyethylene encasement experience corrosion, that
pipe surfaces under intact polyethylene encasement experience corrosion, and that corrosion
occurring under intact polyethylene encasement can not be mitigated by cathodic protection due
to the shielding created by the unbonded encasement, see Figure 5, (Fitzgerald, 1968; Garrity
et al., 1989; Noonan, 1996; Szeliga and Simpson, 2001; Spickelmire, 2002). The opponents
further indicate that corrosion under intact polyethylene encasement cannot be detected by above
ground corrosion monitoring methods (e.g., pipe-to-soil potential surveys) and corrosion under
intact polyethylene will go undetected until failure (Szeliga and Simpson, 2003). Thus,
opponents favor direct bonded coatings and test stations.

Comment [m30]: Make bullets of these item ,
like abve

Comment [m31]:

The opponents of using polyethylene encasement often reference the following three national
documents as supporting documentation of their position. The first is position:
•
•

The NACE International’s RPO 169-2002 Recommended Practice RP0169-2002
“Control of External Corrosion on Underground or Submerged Metallic Piping Systems.”
RPO 169 requires a tight bonded dielectric coating for Systems”;
buried pipeline applications and indicates that unbonded coatings (polyethylene
encasement is considered an unbonded coating) can create electrical shielding of the
pipeline that could jeopardize the effectiveness of the cathodic protection system. The
second is The Code of Federal Regulations (CFR) Title 49 parts Parts 192 and 195
(October 1, 2002) as enforced by the U. S. Department of Transportation’s Office of

B–6

Comment [m32]: The correct reference is
RP0169-2002 (it is a zero not an “O”).

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

•

Pipeline Safety. 49 CFR 192 and 195 does not allow unbonded coatings as an acceptable
corrosion mitigation technique for federally regulated pipelines. Federally regulated
pipelines include pipelines which transport natural gas or hazardous Safety;
liquids. It should be noted that water pipelines are not federally regulated. The third is
The Docket No. OPS-5A (Federal Register Vol. 36, No. 166 – Thursday, August 26,
1971).

While the 3 documents were primarily developed for the oil and gas industry. RP0169 requires a
tight bonded dielectric coating for buried pipeline applications and indicates that unbonded
coatings (polyethylene encasement is considered an unbonded coating) can create electrical
shielding of the pipeline that could jeopardize the effectiveness of the cathodic protection
system. The 49 CFR 192 and 195 do not allow unbonded coatings as an acceptable corrosion
mitigation technique for federally regulated pipelines, and federally regulated pipelines include
pipelines which transport natural gas or hazardous liquids. (Water pipelines are not federally
regulated.) In Docket No. OPS-5A, the Office of Pipeline Safety specifically denied a petition to
permit the use of a loose polyethylene encasement for cast and ductile iron pipes as an alternative
method of corrosion control, and as indicated by 49 CFR 192 and 195 this is the Office of
Pipeline Safety’s current position.
Proponents of polyethylene encasement correctly point out that in order for corrosion monitoring
and cathodic protection systems to be effective, the facilities must be actually used and
maintained. They contend that the added expense of constructing the systems, combined with
the effort and expense to maintain them, places an additional burden on the owner/operator,
compared to polyethylene encasement.
In summary, proponents and opponents of using polyethylene encasement agree that corrosion
can occur at locations where holidays in the polyethylene encasement expose the pipe wall to the
soil and that the resulting corrosion can be mitigated by cathodic protection. Proponents and
opponents agree that corrosion can take place under intact polyethylene encasement, however,
they do not agree on the severity of corrosion which that can take place. The opponents indicate
the potential benefits of a corrosion monitoring system far exceed the costs of constructing it
concurrently with the pipeline, and there is minimal risk of increasing stray current if the that
under most situations the corrosion reaction occurring under intact polyethylene encasement will
be stifled and significant corrosion does not occur pipeline is made electrically continuous at the
joints. The opponents indicate that the corrosion reaction under intact polyethylene encasement
is not stifled, significant corrosion can occur, and cathodic protection cannot be used to mitigate
the corrosion.
Bonded Dielectric Coatings
Bonded dielectric coatings can be and have been successful applied to ductile iron pipe (Szeliga
et al., 1993; Garrity et al., 1989; Pimentel, 2001; Brander, 2001; Lieu and Szeliga, 2002; Fogata,
2003). AWWA M41 – Ductile Iron Pipe and Fittings lists tight bonded coatings as an alternative
corrosion mitigation method for ductile iron pipe. Coatings similar to those applied to steel pipe
can be applied to ductile iron pipe, however, but special methods for surface preparation and

B–7

Comment [m33]: This is for oil and gas, it does
not mean it is applicable…there are lots of other
requirements in the CFR’s that are also not followed
in the water industry. Unless you are willing to
accept the entirety of the requirements, you might
want to tone down the use of these CFR’s. (e.g. CP
is required, monitoring is required, recordkeeping is
required, etc., etc.). This is a slippery slope you
might not want to go down all the way.

Comment [m34]: Suggest adding a paragraph
containing arguments against non-polyethylene
encasement approach

Comment [m35]: Suggest noting that the
advocares of this position usually make no
distinction among the pipelines where it applies,
regardless of whether small distribution lines or
major transmission lines are considered.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

cleanliness must be applied. Preparation guidelines for the surface of steel pipe generally (Steel
Structures Painting Council a.k.a. SSPC) cannot be used for ductile iron pipe. This is because
the steel surface preparation standards for steel do not represent the same levels of cleanliness on
iron due to the differences in the microstructure (particularly for Delavaud cast pipe). In
addition, application of steels standards can lead to overblasting and damage to the iron surfaces
which negate/preclude the application of thin film liquid applied coating systems. In 2000, the
National Association of Pipe Fabricators, Inc. (NAPF) published a standard for surface
preparation for ductile iron pipe and fittings (NAPF 500-03, 2000). Prior to the NAPF standard,
there were no national standards for the surface preparation of ductile iron pipe and most
organizations had to write their own surface preparation and coating specifications.
Ductile iron pipe manufactures and the Ductile Iron Pipe Research Association (DIPRA) often
contend that the expenses of tight bonded dielectric coatings are not generally warranted (Stroud,
1989).
Discussion

Comment [m36]: What is the purpose of this
statement? What is the opposing position on the
issue? You need to put in something here to
complete the thought

It must should be noted that there are several important issues which that influence our
Reclamation’s position relative to corrosion control. We will present these issues These issues
are presented below prior to discussing the underlying issue of this document, that being the use
of polyethylene encasement as a corrosion control method. Reclamation projects typically
require a life of 50 years or greater. Reclamation work can involve both transmission and
distribution pipelines. In relation to distribution pipelines; , transmission pipelines tend to be
larger in diameter, are more critical in nature, elements of the infrastructure, have greater
consequences associated with failure, and have fewer appurtenances (e.g., household services).
Therefore, our this evaluation and the position is focused presented focus on transmission
pipelines requiring a minimum 50 year life. Our position life of 50 years. Positions on the use
of corrosion monitoring systems and protective coatings are presented below.

Comment [m37]: With proper inspection and
maintenance, infrastructure should have an indefinite
life…you need to talk about maintenance issues.

Corrosion Monitoring Systems
Irrespective of the amount of environmental testing that is conducted prior to pipeline design,
there is always a potential for a buried pipeline to have corrosion related corrosion-related
problems. Without a corrosion monitoring system, corrosion related corrosion-related problems
can be difficult to detect prior to a corrosion related corrosion-related failure. If a corrosion
related corrosion-related problem is identified, the corrosion monitoring system allows a means
to investigate and address the problem. Without a corrosion monitoring system the options
available to identify, investigate, and address corrosion related corrosion-related problems are
limited. It should be noted that providing positive electrical continuity of a pipeline will increase
the probability of pipeline corrosion resulting from long line and/or stray currents. However, the
corrosion monitoring system can be used to investigate, identify, and mitigate long line and stray
current corrosion. The benefits of a corrosion monitoring system far exceed the risks. Our
position has been and continues to be that buried pipelines be installed with corrosion monitoring
systems.

B–8

Comment [m38]: What kind of test stations are
you talking about? 2 wire or 4 wire (line
drops)…you need to be more specific.

Comment [gecb39]: What about ER probes?
Rohrback Cosasco has them part number 620DIS100-25 for about $350 each and they work very
well.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Protective Coatings
For the purpose of this report, polyethylene encasement is considered a protective coating (its
intended function is to protect the pipe from corrosion) and the 1-mil asphaltic coating applied to
ductile iron pipe is not considered a corrosion control or barrier protective coating for the
exterior of a buried pipeline.
Buried metallic pipelines have the potential to corrode and typically require some form of
corrosion protection. Without a protective coating the remaining corrosion protection alternative
is cathodic protection. A bare pipe can be adequately protected with a cathodic protection
system, however, the amount of current required to protect a bare pipeline is significantly greater
than the amount of current required to protect a well coated well-coated pipeline. The larger
current requirement results in a larger number of cathodic protection ground beds (locations at
which the protective current is injected into the ground) which increases the design, installation,
operation and maintenance, and power requirements associated with the cathodic protection
system.
Another important consideration is the effect the cathodic protection may have on buried,
adjacent, metallic structures. In addition to existing structures, future development along the
pipeline should be considered as future development tends to increase the number of buried
metallic structures adjacent to the pipeline. The probability of a cathodic protection system
negatively effecting, by cathodic interference, existing and future buried adjacent structures is
significantly increased with a bare pipeline.
Therefore, our position has been and continues to be that buried pipelines be installed with
protective coatings and that the protective coatings be compatible with cathodic protection.
Polyethylene Encasement
The major controversies related to ductile iron pipe involve the effectiveness of polyethylene
encasement as a corrosion mitigation method and the compatibility of polyethylene encasement
and cathodic protection. The technical disagreements generally are focused on the occurrence of
corrosion under intact polyethylene encasement and the mitigation of that corrosion by the use of
cathodic protection.
As with bonded dielectric coatings, installed polyethylene encasement will not be holiday free.
Holidays within the polyethylene encasement can occur during manufacturing, installation,
and/or deterioration with time. At holidays the pipe wall is exposed to the soil and corrosion will
occur as governed by the corrosion characteristics of the soil. It is widely accepted that
corrosion can occur on the pipe wall opposite of polyethylene encasement holidays and that this
corrosion can be mitigated by cathodic protection.
DIPRA has an inspection program where they have conducted a number of inspections on
operating pipelines with polyethylene encasement, encasement; the inspection program indicates
positive results with the use of polyethylene encasement (Stroud, 1989).

B–9

Comment [gecb40]: IT IS AN ECASEMENT
NOT A COATING.

Comment [gecb41]: Based on the cost of
cathodic protection, you can show that from an
economic standpoint you should never pay more
than $3 per square foot for a coating because you can
cathodically protect it for that amount. Reference:
G.E.C. Bell, Value Engineering and Corrosion
Control, AWWA Cal-Nevada Section, Spring
Meeting, April 10, 1997, San Jose, CA.

Comment [gecb42]: Use the word stray current
(since you use it elsewhere in the document) and
show a schematic. Stray current is a design issue
and with proper design and testing, is easily
mitigated. Since you reference the oil and gas CFR,
this is also required and not a big deal.
Comment [m43]: Suggest adding a sentence
summarizing the converse of the previous two
paragraphs, to emphasize that a highly efficient and
compatible coating makes cathodic protection more
economical and safer by reducing the potential for
stray current from the system to affect other
underground facilities.
Comment [gecb44]: I do not see how this
follows from the facts. As stated above, stray
current is not the death knell of a project. This
statement is not supported by facts…possibly
economics, but it depends on the price of coatings.
Comment [m45]: Suggest adding some
subheading for this section to highlight key points
and improve readability.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Others have reported that the rate of corrosion corrosion under undamaged polyethylene
encasement is very low (Schiff and McCollom, 1993). A continuation of the Schiff and
McCollom work indicates that corrosion under undamaged polyethylene encasement has
remained low, that the corrosion rate under undamaged polyethylene is an order of magnitude
less than that experienced outside the polyethylene within sand backfill, and that cathodic
protection is effective under undamaged polyethylene (Bell, 2003).
Corrosion occurring under intact polyethylene encasement has been reported (Szeliga and
Simpson, 2003; Spicklemire, Spickelmire, 2002; Fogata, 2003). It is widely accepted that the
presence of foreign material (e.g., soil) between the polyethylene encasement and pipe surface
results in corrosion of the pipe surface in contact with the foreign material. Several of the Cast
Iron Pipe Research Association (CIPRA) and Ductile Iron Pipe Research Association (DIPRA)
excavations indicate that corrosion pits have been observed under foreign material on the pipe
wall which was located under undamaged polyethylene encasement. (CIPRA, 1968; CIPRA
1969; DIPRA, 1981; Stroud, 1989). The CIPRA/DIPRA reports of the inspections typically
have speculated that the corrosion under foreign materials had stopped (CIPRA, 1968; CIPRA,
1969; DIPRA, 1981). The ductile and grey cast iron pipelines inspected in San Diego during the
CIPRA 1968 and DIPRA 1981 excavations have experienced corrosion related corrosion-related
failures (Fogata, 2003). The San Diego cast iron pipeline was one of the initial installations of
polyethylene encasement, installed in 1961, and the soil in which the pipelines were buried are
considered very corrosive (DIPRA, 1981).
As recommended by the 1993 Schiff and McCollum McCollom report, corrosion resistance
probes were placed under polyethylene encasement at various distances from a slit (holiday)
intentionally cut in the polyethylene encasement (McCollom, 2003). The probes were installed
at a location along the pipeline where ground water was expected at pipe depth. This work
indicates that cathodic protection may not be effective in mitigating corrosion occurring under
undamaged polyethylene located adjacent to holidays in the polyethylene encasement.
Dielectric coatings allow penetration of moisture, gases, and ionized substances, the rates at
which they allow this substances. The penetration rates are dependent on coating characteristics,
environmental conditions, and time (Toncre, 1981). It has been shown that metal exposed at
holidays in dielectric coatings are is anodic to metal under intact dielectric coatings(Craig and
Olson, 1976). This demonstrates the conductive abilities of dielectric coatings and that they
generally are not perfect electrical insulators.
Corrosion and the mitigation of corrosion under disbonded coatings has have been a concern
within the corrosion industry for a number of years and, therefore, there has been research
conducted in these areas. Corrosion can occur under disbonded dielectric coatings (Koehler,
1971 and 1977; Fessler et al., 1983; Leidheiser, 1983; Scantlebury et al., 1983; Jack et al., 1994;
National Energy Board, 1996; Beavers and Thompson, 1997; Daikow et al., 1998; Song et al.,
2003; FHWA, 2001). Unfortunately, the studies conducted have included common coatings
used on steel pipe and have not included the polyethylene encasement used on ductile iron pipe.
However, there are studies which that have included a polyethylene tape system for pipelines.
The polyethylene tape is composed of a polyethylene film laminated with an adhesive/mastic.
The adhesive/mastic is used to provide a bond to the metal substrate and, therefore, the
B – 10

Comment [m46]: See inserts above. The
damaged/undamaged work is not really complete
and needs to be discussed in terms that perhaps the
use of coupons caused the tears to be worse than
they are. See comments below.
Comment [m47]: Did any of these projects have
cathodic protection?

Comment [m48]: Suggest reorganizing by
moving last sentence to start of paragraph.

Comment [m49]: This work is preliminary and
the actual reason for the changes has not been
identified. Further, the size of the probes themselves
may be a factor the at skews and accelerates the
corrosion since the shape does not allow the
encasement to lay flat against the pipe surface. That
is, the pipe surrogate (electrical resistance probe)
may not be a good surrogate for the pipe wall.

Comment [m50]: Suggest stating that the
discussion is extrapolating the finding from studies
on pipeline tape because the polyethylene backing of
the tape is the most similar studied material to
polyethylene sheet. He notes that this would likely
be challenged by DIPRA.
Comment [m51]: Isn’t polyethylene tape more
flexible and pliable than polyethylene encasement?
Since the mechanical and physical properties will
greatly impact the moisture permeation, shouldn’t
you compare/state these properties as well as simply
the material type.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

polyethylene tape is considered a tight bonded dielectric coating. The polyethylene tape systems
are generally applied by the application of with one to three polyethylene tape layers. These
studies indicate that most dielectric coatings are capable of conducting current. However,
current, but not the polyethylene tape is one dielectric coating that the studies typically indicate
does not conduct current tape, and cathodic protection is not effective under disbonded
polyethylene tape away from holidays (Barlow and Zdunek, 1994; National Energy Board, 1996;
Beavers and Thompson, 1997). Furthermore, it has been reported that oxygen readily diffuses
through polyethylene tape systems (Beavers and Thompson, 1997). There have been cases
where corrosion has occurred under disbonded polyethylene tape when testing indicated that the
pipeline was receiving adequate levels of cathodic protection (National Energy Board, 1996;
Beavers and Thompson, 1997).

Comment [m52]: The purpose of surface
preparation is to promote adhesion of a bonded
coating. For some coatings, little or no surface
preparation is required. I can also argue that since
polyethylene encasement is an unbonded coating that
adhesion is not a requirement. I think what you
actually are getting at surface cleanliness

AWWA C105 requires the removal of obvious surface contamination but does not address less
obvious surface contamination. Proper surface preparation is critical for the long term long-term
success of protective coatings. An important step in surface preparation is the removal of
contaminates from the surface to be coated. Surface contaminates include rust, chlorides, oil,
grease, soil, and etc. Surface contaminates can effect adhesion of bonded coatings and they can
promote corrosion of the surfaces beneath bonded or unbonded coatings. Since polyethylene
encasement is installed on pipe at the construction site, there are opportunities for surface
contaminates to collect on the pipe during storage, transportation, and installation. Because
surface contaminates can and do promote corrosion, investigations should be conducted within
this area. This is an area where further investigation might shed more light on the potential for
corrosion under intact polyethylene.

Comment [m53]: Isn’t this a construction
inspection issue? Can the same thing occur to pipes
with bonded coatings?

The above indicates that long term long-term corrosion can occur under intact polyethylene
encasement with or without the presence of foreign material. Therefore, there must be an active
mechanism which that replenishes moisture and/or dissolved oxygen within the annulus between
the polyethylene encasement and pipe wall. There are two methods in mechanisms by which
moisture and/or oxygen can enter the annular space. Moisture and oxygen can enter the annular
space through holidays in the polyethylene encasement or through the polyethylene encasement
itself. Therefore, corrosion under intact polyethylene encasement is highly dependent upon the
diffusion of moisture and oxygen through the polyethylene encasement, and/or transportation of
moisture and oxygen through polyethylene encasement holidays. The dominate dominant route
is expected to be through the holidays. Once in the annulus, moisture can be transported within
the annulus by by free flow and/or capillary action.

Comment [m57]: What forms the annulus?
Doesn’t the weight of the soil push the polyethylene
up against the pipe?

Time has provided cases where Successful applications of polyethylene encasement has been
successful and where it has not been successful. have been reported. Unsuccessful applications
have also been reported. To complicate matters further, the nature of the corrosion experienced
on cast and ductile iron pipe is such that the recognition of corrosion related corrosion-related
failures is not readily apparent and, as such, corrosion failures may not be fully accounted for. It
is unfortunate, but after 40 years of use there are still basic issues regarding the use of
polyethylene encasement that must be addressed.

B – 11

Comment [m54]: I would submit that unless the
surface contaminants support the reduction reaction,
then so long as oxygen is excluded, corrosion is
mitigated. Chloride is certainly a depolarizing agent
and should be excluded.
Comment [m55]: With or without cathodic
protection? Can’t the same thing happened with
other coatings? What about the application problems
with coatings…not just on DIP but on all surfaces?
Coatings are not fail safe.
Comment [m56]: Reference? Or has this been
measured?

Comment [m58]: Suggest considering the
positions of the Europeans and other international
groups on the issue. He states that it is his
understanding that polyethylene encasement has not
been accepted as the sole form of protection for
ductile iron in Europe. Also consider noting that in
the U.S., the situation with respect to polyethylene
encasement seems to have resulted in the evolution
of 3 camps: (1) those outright rejecting polyethylene
encasement and treating of ductile iron pipe the same
as steel pipe, (2) those completely accepting
polyethylene encasement, and (3) those somewhere
between these two positions. This would seem to
reinforce the conservative position recommended by
Reclamation, namely, limiting the use of
polyethylene encasement until research answers the
fundamental questions posed in the
Recommendations section.
Comment [m59]: Just like every other corrosion
control system…cathodic protection is not fool
proof, coatings are not perfect. The most fail safe
and perhaps cost effective is clean backfill.
Comment [gecb60]: Further, it is my
experience that the failures that are reported are not
fully investigated to identify root causes beyond
simple corrosivity testing…again, my experience is
that there are typically other factors that lead to the
failure beyond simply soil corrosivity.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Conclusions and Recommendations
Conclusions:
1. The use of polyethylene encasement for corrosion protection of ductile iron pipe is a very
controversial subject.
2. Graphitic corrosion can occur on cast and ductile iron pipelines. Graphitic corrosion is
difficult to visually detect and as a result failures resulting from graphitic corrosion are
often not recognized as corrosion related failures.
3. There are two general categories of corrosion which can occur with the use of
polyethylene encasement. Corrosion can occur on the pipe wall opposite holidays in the
polyethylene encasement and corrosion can occur on the pipe wall under intact
polyethylene encasement.
4. Corrosion opposite holidays in the polyethylene encasement is highly dependent upon the
corrosion characteristics of the soil.
5. Corrosion under intact polyethylene encasement is highly dependent upon the availability
of oxygen under the intact polyethylene encasement.
6. The corrosion rates associated with the two categories are generally not the same. With
all other factors being equal, it would be expected that the corrosion cell occurring
opposite of holidays will have a higher corrosion rate than the corrosion cell occurring
under intact polyethylene encasement (this is not applicable to microbiologically
influenced corrosion).
7. The corrosion experienced on the pipe wall opposite holidays in the polyethylene
encasement can be mitigated with the application of cathodic protection.
8. Detecting corrosion that occurs under intact polyethylene encasement with above ground
monitoring methods is very unlikely.
9. Mitigating corrosion that occurs under intact polyethylene encasement with cathodic
protection is very unlikely.
Recommendations:
1. Do not use polyethylene encasement until the following issues are addressed to our
satisfaction:
a. What are the mechanisms and what is the extent of corrosion occurring on
metallic surfaces under intact polyethylene encasement? This should include
microbiologically influenced corrosion.

B – 12

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

b. Is cathodic protection effective in mitigating corrosion occurring under intact
polyethylene encasement?
2. Continue the evaluation of the corrosion mitigation alternatives listed in the Corrosion
Prevention Criteria and Requirements table, with the focus being on the other pipe
alternatives listed.
3. Conduct research to address the issues identified in Recommendation 1. Research
conducted on existing structures could provide a wealth of data. The performance of
protective coatings and their compatibly with cathodic protection is considered very
important; the results could impact what protective coatings can be used with all metallic
pipe alternatives. Surface contaminates beneath unbonded dielectric coating should be
investigated.
4. Form partnerships such that the research can be efficiently performed. Partners from
federal, state, local, and industry should be sought. In addition, partners from Canadian
organizations should be sought. Canadian organizations have and continue to research
common areas of interest.
Conclusions:
1. The literature review here indicates that the use of polyethylene encasement for corrosion
protection of ductile iron pipe is still a controversial subject.
2. Graphitic corrosion can occur on grey cast and ductile iron pipelines, but is frequently not
recognized as a root cause of failure.
3. For ductile iron, with PE and no cathodic protection:
a. Corrosion can occur on the pipe wall adjacent to holidays in the polyethylene
encasement and on the pipe wall under intact polyethylene encasement;
b. Corrosion that occurs adjacent to holidays in the polyethylene encasement is
dependent upon the corrosion characteristics of the soil;
c. Corrosion under intact polyethylene encasement (as well as most all corrosion
cells) is dependent upon the availability of oxygen under the intact polyethylene
encasement;
d. It would be expected that the corrosion cell occurring adjacent to holidays will
have a higher corrosion rate than the corrosion cell occurring under intact
polyethylene encasement.

B – 13

Comment [m61]: The conclusion might be more
effective as a Summary & Conclusion section, with
narrative reviewing major issues and then the
conclusion (all but one of the numbered paragraphs
in the original draft is about encasement, and #6
refered to micrbiologically induced corrosion, which
is only mentioned in the appendix. (Need to include
in body of text.)
Comment [m62]: This may be true but it is not
clear why this is important enough to listed as a
conclusion. I assume that it is related to the fact that
this makes it difficult to get a proper count of
“corrosion failures” and this make it hard to
evaluated the various choices you might have for
constructions.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

4. For ductile iron, with PE and cathodic protection
e. The corrosion experienced on the pipe wall adjacent to holidays in the
polyethylene encasement can be mitigated with the application of cathodic
protection;
f. Mitigating corrosion that occurs under intact polyethylene encasement with
cathodic protection is inconclusive and additional research is needed.
5. Detecting corrosion that occurs under intact polyethylene encasement with above ground
monitoring methods is, as with any disbonded coating, difficult.
Recommendations:
1. Use polyethylene encasement, as per revised (2004) Table 1.
2. There are a number of issues that need to be addressed, including the following:
a. What are the mechanisms and what is the extent of corrosion occurring on
metallic surfaces under intact polyethylene encasement? This should include
microbiologically influenced corrosion.
b. Is cathodic protection effective in mitigating corrosion occurring under intact
polyethylene encasement?
c. The performance of protective coatings and their compatibility with cathodic
protection, with variables such as surface contaminates beneath unbonded
dielectric coating, and the effects of pipe zone backfill on PE should be
investigated
3. Conduct research to address the issues identified in Recommendation 2.
4. Continue the evaluation of the corrosion mitigation alternatives listed in the Corrosion
Prevention Criteria and Requirements Table 1, for the other pipe alternatives listed.
5. Form partnerships, so that the research can be most efficiently performed. Partners from
federal state, local, and industry should be sought. In addition, partners from Canadian
organizations, who continue to research common areas of interest, should be sought.

Comment [m63]: Suggest presenting the
recommendations as a short narrative, but leaving 1a
and 1b as stated (because these are profound
questions). He adds that a related question is what is
the relationship between polyethylene performance
and pipe bedding and backfill materials (At one time
imported pipe zone materials were required to be
fine-grained to minimize damage to polyethylene.
But resent versions of AWWA C105 don’t include
these limitations - and confirmed by DIPRA, without
any evidence of research to support this change.)
Also, the recommendations should include how
Table 1 would look if polyethylene encasement is
deleted, and reiterate that Reclamation’s other
requirements for corrosion monitoring and cathodic
protection would still apply. The call for additional
research (3 and 4) is apropiate but may deserve
further consideration if Reclamation is obligated to
perform the recommend actions.
Comment [gecb64]: Does this include with or
with out CP, See graphs from above. Why do you
need to know the mechanism if corrosion control is
effective?
Comment [gecb65]: If you are going to talk
about this, you had better discuss this earlier and get
all of the information on the table.
Comment [m66]: Reword as a statement, rather
than a question
Comment [m67]: Reword to fit into the flow
here.
Comment [gecb68]: Agreed, but you need to
define the conditions under which the measurements
are made. In general, I would say that your criteria
are too conservative, but Reclamation can make
whatever internal design requirements that they
want…at the end of the day, it is your pipe.
Comment [m69]: The cited references are
abundant, bordering on too many.

Cited References
Avner, S.H., 1974. Introduction to Physical Metallurgy, Second Edition, McGraw-Hill.
AWWA M41, 2003. Ductile-Iron Pipe and Fittings, AWWA Manual M41, Second Edition,
American Water Works Association, Denver, CO.

B – 14

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Barlo, T.J. and Zdunek, A.D., 1994. "Cathodic Protection Under Disbonded Coatings,"
American Gas Association, Arlington, VA, January.
Beavers, J.A and Thompson, N.G., 1997. "Corrosion Beneath Disbonded Pipeline Coatings."
Materials Protection, pp. 13 – 19, April.
Bell, G., 2003. MJ Schiff and Associates, Inc. Personal communication.
Bonds, R.W., 1997. "Stray Current Effects on Ductile Iron Pipe." Ductile Iron Pipe Research
Association, August.
Brander, R., 2001. "Water Pipe Materials in Calgary, 1970 – 2000," American Water Works
Association - Infrastructure Conference Proceedings.
CANMET, 1983. Underground Corrosion of Water Pipes in Canadian Cities, Case: The City
of Calgary, Final Report, Report No. ENG-83/240, Canada Centre for Mineral and Energy
Technology; Energy, Mines and Resources Canada, Ontario, Canada, August.
Chambers, G., 1983. "Analysis of Winninpeg's Watermain Failure Problem." City of
Winnipeg Works and Operations Division Waterworks, Waste and Disposal Department,
February.
CIPRA, 1968. A Report on Observation of Corrosion Protection of Cast Iron Pipe by Loose
Polyethylene Wrap, San Diego, California, Cast Iron Pipe Research Association, Oak Brook,
IL, December.
CIPRA, 1969. Inspection of Cast Iron Pipe Protected from Corrosive Soil since December,
1959 by Loose Polyethylene Tube, Philadelphia, Pennsylvania, Cast Iron Pipe Research
Association, Oak Brook, IL, August.
Clark, C.M., 1972. "Stray and Impressed Current Tests on Polyethylene-Encased Cast Iron
Pipe," Presented at the National Association of Corrosion Engineers Western Region
Conference, October.
Craig, B.D. and Olson, D.L., 1976. "Corrosion at a Holiday in an Organic Coated-Metal
Substrate System," Corrosion – NACE, Vol. 32, No. 8, pp. 316 – 321, August.
Diakow, D.A., Van Boven, G.J. and Wilmott, M.J., 1998. "Polarization Under Disbonded
Coatings: Conventional and Pulsed Cathodic Protection Compared," Materials Protection, pp.
17 - 23. May.
DIPRA, 1981. A Report on Inspection of Cast Iron Pipe and Ductile Iron Pipe Protected by
Loose Polyethylene Encasement, San Diego, California, Ductile Iron Pipe Research
Association, Oak Brook, IL, October.

B – 15

Comment [m70]: location?

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Fessler, R.R., Markworth, A.J. and Parkins, R.N., 1983. "Cathodic Protection Levels Under
Disbonded Coatings." Corrosion – NACE, Vol. 39, No. 1, pp. 20 – 25, January.
FHWA, 2001. Corrosion Cost and Preventive Strategies in the United States, Report No.
FHWA-RD-01-156, Federal Highway Administration, McLean, VA, 2001.
Fitzgerald, J.H, 1968. "Corrosion as a Primary Cause of Cast-Iron Main Breaks," Journal
American Water Works Association. Vol. 60, No. 8, pp. 882 – 897, August.
Fogata, M., 2003. City of San Diego, CA. Personal communication.
Garrity, K.C., Jenkins, C.F. and Corbett, R.A., 1989. "Corrosion Control Design
Considerations for a New Well Water Line," Materials Performance, pp. 25 – 29, August.
Gummow, R.A., 1978. "Corrosion and Cathodic Protection of Underground Metallic Water
Piping Systems, " Presented at the Western Canada Water and Sewage Conference,
September.
Jack, T.R. et al., 1994. "Cathodic Protection Potential Penetration Under Disbonded Pipeline
Coating," Materials Protection, pp. 17 – 21, August.
Jakobs, J.A. and Hewes, F.W., 1987. "Underground Corrosion of Water Pipes in Calgary,
Canada." Materials Performance, pp. 42 – 49, May.
Koehler, E.L., 1971. "Corrosion Under Organic Coatings,” Localized Corrosion, NACE 3,
Staehle, R.W., Ed., NACE International, Houston, TX, pp. 117-133.
Koehler, E.L., 1977. "The Influence of Contaminants on the Failure of Protective Organic
Coatings on Steel," Corrosion - NACE, Vol. 33, No. 6, pp. 209 – 217, June.
Leidheiser Jr., H., 1983. "Whitney Award Lecture – 1983, Towards a Better Understanding
of Corrosion Beneath Organic Coatings," Corrosion - NACE, Vol. 39, No. 5, pp. 189 – 201,
May.
Lieu, D. and Szeliga, M.J., 2002. "Protecting Underground Assets with State-of-the-Art
Corrosion Control," Materials Performance, pp. 24-28, July.
Lisk, I., 1997. "The Use of Coatings and Polyethylene for Corrosion Protection." Water
Online, January.
Makar, J.M., Desnoyers, R. and McDonald, S.E., 2000. "Failure Modes and Mechanisms in
Gray Cast Iron Pipe," NRCC-44218, National Research Council Canada, Ontario, Canada.
McCollom, B., 2003. Bartlett and West Engineers. Personal communication.

B – 16

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

NAPF 500-03, 2000. NAPF 500-03, Surface Preparation Standard for Ductile Iron Pipe and
Fittings Receiving Special External Coatings and/or Special Internal Linings, National
Association of Pipe Fabricators, Inc., Edmond, OK, March.
National Energy Board, 1996. Report of The Inquiry, Stress Corrosion Cracking on
Canadian Oil and Gas Pipelines, National Energy Board, Alberta, Canada, November.
Noonan, J.R., 1996. "Proven Economic Performance of Cathodic Protection and
Anticorrosion Systems in the Water Pipeline Industry," Bulletin No. 6-6, Steel Plate
Fabricators Association, Des Plaines, IL, June.
Pimentel, J.R., 2001. "Bonded Thermoplastic Coating for Ductile Iron Pipe," Materials
Performance, pp. 36 – 38, July.
Romanoff, M., 1957. “Underground Corrosion,” National Bureau of Standards Circular 579,
US Govt. Printing Office, Washington D.C.
Romanoff, M., 1968. "Performance of Ductile-Iron Pipe in Soils,” Journal American Water
Works Association. Vol. 60, No. 6, pp. 645 – 655, June.
Scantlebury, J.D. et al., 1983. "Simulated Underfilm Corrosion of Coated Mild Steel Using
and Artificial Blister," Corrosion – NACE, Vol. 39, No. 3, pp. 108 – 112, March.
Schiff, M.J., and McCollom, B., 1993. "Impressed Current Cathodic Protection of
Polyethylene Encased Ductile Iron Pipe," Paper No. 583, Presented at Corrosion93, The
NACE Annual Conference and Corrosion Show.

Comment [m71]: location?

Smith, W.H., 1963. "A Report on Corrosion Resistance of Cast Iron and Ductile Iron Pipe."
Cast Iron Pipe News, Vol. 35, No. 3, 16 – 29, May-June.

Comment [m72]: page?

Smith, W.H., 1970. "Cast Iron Pipe Design, Environment, Life,” Printed from Journal of the
New England Water Works Association, Vol. 84, No. 4.
Song, F.M. et al., 2003. "Corrosion Under Disbonded Coatings Having Cathodic Protection,"
Materials Performance, pp. 24-26, September.
Spickelmire, B., 2002. “Corrosion Considerations of Ductile Iron Pipe – A Consultant’s
Perspective 2002,” Presented at the Appalachian Underground Corrosion Short Course, May.
Stroud, T.F., 1989. "Corrosion Control Measures for Ductile Iron Pipe," Paper No. 585,
Presented at the Corrosion89, April.
Szeliga M.J. and Simpson, D.M., 2001. "Corrosion of Ductile Iron Pipe: Case Histories,"
Materials Performance, pp. 22 - 26. July.

B – 17

Comment [m73]: location?

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Szeliga M.J. and Simpson, D.M., 2003. "Evaluating Ductile Iron Pipe Corrosion." Materials
Performance, pp. 22 – 28, July.
Szeliga, M.J., Brandish, B.M. and Hart, G.M., 1993. "The Application of Corrosion Control
Methods to Large Diameter Water Mains," Presented at The Tri-Association Conference,
AWWA Chesapeake Section, August.
Toncre, A.C., 1981. "The Relationship of Coatings and Cathodic Protection for Underground
Corrosion Control." Underground Corrosion, ASTM STP 741, Edward Escalante, Ed.,
American Society for Testing and Materials, pp. 166 – 181.

General References
Andrews, E.N., 1975. "Loose Polyethylene Sleeving in the Corrosion Protection of Buried
Cast Iron Pipe," Anti-Corrosion, pp. 13 -15, November.
Ash, G., 1998. "Polyethylene Encasement of Buried Conduit," ASCE, Proceedings of the
1998 Pipeline Division Conference, pp. 180 - 186.
ASTM, 2000. “A674-00, Standard Practice for Polyethylene Encasement for Ductile Iron Pipe
for Water or Other Liquids," American Society for Testing and Materials.
ASTM, 1972. “A674-72, Standard Recommended Practice for Polyethylene Encasement for
Gray and Ductile Cast Iron Pipe for Water or Other Liquids," American Society for Testing
and Materials.
AWWA, 1972. "AWWA C105-72, American National Standard for Polyethylene Encasement
for Gray and Ductile Cast-Iron Piping for Water and Other Liquids," First Edition, American
Water Works Association.
AWWA, 1999. "AWWA C105-99, American National Standard for Polyethylene Encasement
for Ductile-Iron Pipe Systems," American Water Works Association.
Bellefeuille, R., 2000?. "A Contractor’s Experience Installing Thermoplastic-Coated Ductile
Iron Pipe as Opposed to PVC-Tape Coated Pipe for Cathodically Protected Water Supplies,"
Kohl Excavating, Inc.
Bellefeuille, R., 2001. "Contractor Assesses Benefits of Thermoplastic Coating," Journal
AWWA, pp. 106 – 112, April.
Bianchetti, R., 2003a. East Bay Municipal Utility District, Personal communication.
Bianchetti, R., 2003b. East Bay Municipal Utility District. Letter to Bureau of Reclamation,
June 4.

B – 18

Comment [m74]: The general references should
be mentioned in the body of the text, to better serve
the reader. Also suggests deleting the personal
communications. He states that the combined list of
cited and general reference is the most
comprehensive that he has ever seen in one place on
this subject.
Comment [m75]: For consistance, should add","
after"." here in all references.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Bonds, R., 1991. "Causes, Investigation, and Mitigation of Stray Current Corrosion on Ductile
Iron Pipe," Paper No. 516, Presented at the 1991 NACE Annual Conference and Corrosion
Show.
Bone, L. et al., 2001. "Coating Round Table, The Use of Coatings in Rehabilitating North
America's Aging Pipeline Infrastructure," Pipeline & Gas Journal, February.
BOR, 2003. Value Engineering, Final Report, Lewis and Clark Rural Water Project Raw
Water Pipeline Segments 2 and 3, Bureau of Reclamation, Denver, CO, November.
Corrpro Companies, Inc., 1999. "BRLE, Break Reduction / Life Extension for Cast and
Ductile Iron Water Mains."
Bushyeager, M., 2003. Metropolitan Water District of Southern California, Personal
communication.
Carlsen, R.J., 1973. "Inspection of Polyethylene-Wrapped Cast Iron Pipe Exposed to
Extremely Corrosive Soils for Nine Years," Cast Iron Pipe Research Association, May.
Carlsen, R.J., 1974. "A Report on Observation and Evaluation of Polyethylene Encasement
for Ductile Iron Pipe in a High Density Stray Current Field, Orange, California," Cast Iron
Pipe Research Association.
CIPRA, 1971. "Record of Gray and Ductile Cast Iron Pipe Installation Protected by 8-mil
Loose Polyethylene Encasement."
CIPRA, 1973. "Operational Report #7, Stray and Impressed Current Test Site, Overton,
Nevada," Cast Iron Pipe Research Association, October.
Clark, C.M., Higgins, M.J. and Dieter, J.R., 1976. "Preliminary Review of Stray Current
Protection on Cast and Ductile Iron Pipe," Cast Iron Pipe Research Association.
Cobrin, R., 2003. Denver Water, Personal communication.
Construction, 1994. "Looking Into the Future," Construction, pp. 10 -12, September.
Cordova, K., 2001. "Cathodic Protection Program of the Aurora, Colorado, Water Division,”
Materials Performance, pp. 28 -30, July.
Dechant, D., 2003a. Northwest Pipe Company. Letter to Bureau of Reclamation, August 6.
Dechant, D., 2003b. Northwest Pipe Company. Letter to Bureau of Reclamation, August 7.
Dechant, D., 2003c. Northwest Pipe Company. Letter to Bureau of Reclamation, May 14.
Dechant, D., 2003d. Northwest Pipe Company. Letter to Bureau of Reclamation, October 24.

B – 19

Comment [m76]: Cast Iron Pipe Reasearch
Ass...

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

DIPRA, 1998. “Inspection Report, Cathodically Protected Ductile Iron Pipe Encased in Loose
Polyethylene, Dickinson, North Dakota, June 10, 1998,” Ductile Iron Pipe Research
Association.
DIPRA, 2000. “Polyethylene Encasement, Effective, Economical Protection for Ductile Iron
Pipe in Corrosive Environments,” Ductile Iron Pipe Research Association.
DIPRA, 2003. “Ductile Iron Pipe News,” Ductile Iron Pipe Research Association,
Spring/Summer.
Doherty, B.J., 1990. "Controlling Ductile-Iron Water Main Corrosion," Materials
Performance, pp. 22 – 28, January.
EBAA Iron, 1993. "Use of Coatings and Polyethylene for Corrosion Protection," EBAA
Connections Technical Data for the Water and Wastewater Professional, GI-3, 9-93.
Edrich, J., Bartels, R. and Spiller, B.J., 2002. "Weighing the Options," Civil Engineering, pp.
48 – 51, August.
Fennell, J.G. and Lawrence, C.F., 2000. "Cathodic Protection of a Large Distribution System:
Why We Did It and What We Found Out," 2000 AWWA, Infrastructure Conference
Proceedings.
Fernandes, E., 2004. San Diego Waste Water, Personal communication.
Ferrigno, A. and Hanson, P., 2004. Ductile Iron Pipe Research Association, Personal
communication.
Freeman, S.R., 1999. “Graphitic Corrosion – Don’t Forget About Buried Cast Iron Pipes,”
Materials Performance, pp. 68 – 69, August.
Galleher, J., 2003. San Diego County Water Authority, Personal communication.
Gerhold, W.F., 1976. "Corrosion Behavior of Ductile Cast-Iron Pipe in Soil Environments,"
Journal American Water Works Association, pp. 674 – 680, December.
Green, B.M., Johnson, F. and De Rosa, J., 1992. “In Situ Cathodic Protection of Existing
Ductile Iron Pipes,” Materials Performance, pp. 32 – 38, March.
Green, B.M., 1993. "Cathodic Protection of Ductile Iron by Retrocat," 1993 AWWA
Distribution System Symposium Proceedings, pp. 81 - 101.
Greenberger, S., 2004. Bureau of Water Portland Oregon, Personal communication.
Grigg, N., 2003. Colorado State University, Personal communication.
Guan, S.W., 2001. "Corrosion Protection by Coatings for Water and Wastewater Pipelines,"
Presented at the 46th Appalachian Underground Corrosion Short Course, May.

B – 20

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Harrington, T., 1993. "Managing a Corrosion Control Program," 1993 AWWA Distribution
System Symposium Proceedings, pp. 53 - 64.
Harris, J., 1972. "The Efficiency of the Polyethylene Sleeve over Cast Iron Pipe in Relation to
Sulfate Reducing Bacteria," Kansas State University.
Hawn, D.E. and Davis, J.R., 1975. "Special Corrosion Investigation Phase I, for City of
Calgary Water Transmission and Distribution System," Caproco Corrosion Prevention, Ltd.,
August.
Hewes, F.W., 1966. "A Survey of Requirements and Costs for Cathodic Protection on 22,000
Miles of Coated Pipeline," Materials Protection, pp. 41 – 46, September.
Hickley, M.E., 1968. "Report No. ChE-82, Laboratory and Field Investigations of Plastic
Films as Canal Lining Materials, Open and Closed Conduits Systems Program," Bureau of
Reclamation, September.
Hoffman, D.A. and Waters, F.O., 1966. "Using Cast Iron Pipe in Highly Corrosive
Environments," Materials Protection, pp. 21 – 22, May.
Horn, L.G. and Thornton, T.B., 2001. "Corrosion and Its Control on Ductile Iron Pipe," 2001
AWWA - Infrastructure Conference Proceedings, pp. 1 - 7.
Howard, D., 2003. Colorado Interstate Gas, Personal communication.
Irias, N.J. and Miller, M.L., 1998. "Cathodic Protection of Cast Iron Pipe," Presented at the
1998 ASCE Pipeline Conference.
Kennedy Jr., H., 1976. "The New Ductile Iron Pipe Standards," Journal American Water
Works Association, pp. 622 – 626, November.
Khoury, O.A. et al., 2003. “San Diego Delivers,” Civil Engineering, pp. 64 – 69, February.
Koehler, E.L., 1984. "The Mechanism of Cathodic Disbondment of Protective Organic
Coatings - Aqueous Displacement at Elevated pH," Corrosion – NACE, Vol. 40, No. 1, pp. 5
– 8, January.
Landers, J., 2003. "Drinking Water, New System to Serve 200,000 in Three Plains States,"
Civil Engineering, pp. 26 – 29, October.
Lawrence, C., 2001. "To CP or Not to CP? That is the Question," 2001 American Water
Works Association - Infrastructure Conference Proceedings.
Lowenberg, H., 2003. Helix Water District, Personal communication.
Makar, J., 1999. "Failure Analysis for Grey Cast Iron Water Pipes," 1999 AWWA Distribution
System Symposium.

B – 21

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Makar, J. and Rajani, B., 2000. "A Methodology to Estimate Remaining Service Life of Grey
Cast Iron Water Mains," Can. J. Civ. Eng. 27, pp 1259 – 1272.
Makar, J.M., 2000. "Prone to Fail," National Research Council Canada, Report No. NRCC44678.
Makar, J.M, 2001. "Investigating Large Gray Cast Iron Pipe Failures: A Step by Step
Approach," National Research Council Canada, Report No. NRCC-44297.
Makar, J.M. "A Preliminary Analysis of Failures in Grey Cast Iron Water Pipes," National
Research Council of Canada.
Makar, J.M. and Chagnon, N., 1999. "Inspecting Systems for Leaks, Pits, and Corrosion,"
National Research Council Canada, Report No. NRCC-42802.
Makar, J.M. and Kleiner, Y., 2000. "Maintaining Water Pipeline Integrity," National
Research Council Canada, Report No. NRCC-43986.
Makar, J.M. and Rajani, B.B., 2000. "Gray Cast-Iron Water Pipe Metallurgy," National
Research Council Canada, Report No. NRCC-44241.
Meletis, E.I. and Hochman, R.F., 1983. “The Effect of Static and Residual Stresses on
Localized Graphitic Corrosion of Gray Cast Iron,” Materials Performance, pp. 37 – 42,
September.
Metz, J.R., and LaBonde, H.C., 1967. "Investigation of Corrosion Protection of Cast Iron Pipe
with Loose Polyethylene Tube, Detroit Michigan," Cast Iron Pipe Research Association,
December.
NACE International, 1995. "Corrosion of Ductile Iron Piping," Szeliga, M.J., Editor, National
Association of Corrosion Engineers.
Newell, R., 2003. Washington Suburban Sanitary Commission, Personal communication.
Palmer, J.D., 1988. “Dealloying Mechanism in Cast and Ductile Iron,” Materials
Performance, p. 58, May.
Pennington, W.A., 1966. "Corrosion of Steel and Two Types of Cast Iron in Soil," Presented
at the 45th Annual Meeting of the Highway Research Board.
Peterson, M.H. and Lennox Jr., T.J., 1973. "A Study of Cathodic Polarization and pH
Changes in Metal Crevices," Corrosion – NACE, Vol. 29, No. 10, pp. 406 – 410, October.
Pimentel, J., 1999?. "Use of Thermoplastic Powder Coating on Ductile Iron Water Pipe by
Seattle Public Utilities," Seattle Public Utilities, Water / Wastewater Engineering Division.

B – 22

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Pimmentel, J., 1998. "Cost Comparison for Bonded Thermoplastic Coating vs. Multi-Layer
Polyethylene Tape Coating for the Port of Seattle, Terminal 18 Project," Seattle Public
Utilities Corrosion Control Team Memorandum, July.
IIT Research Institute, 1967. "Evaluation of Literature on Buried Pipe Corrosion, IITRIB8093-3 (Final Report)," IIT Research Institute, February.
Rajani, B. and Kleiner, Y., 2003. “Protecting Ductile-Iron Water Mains: What Protection
Method Works Best for What Soil Condition?,” Journal American Water Works Association,
Vol. 95, No. 11, pp 110-125, November.
Romanoff, M., 1964. "Exterior Corrosion of Cast-Iron Pipe," Journal American Water Works
Association, pp. 1129 – 1143.
Scarpa, R., 2003. Ductile Iron Pipe Research Association, Personal communication.
Schiff, M.J. & Associates, Inc., 1998. "Southwest Pipeline Project, Cathodic Protection
Troubleshooting, Cathodic Protection Contracts 2-2A, 2-2C and 2-3E," October.
Sears, E.C., 1968. "Comparison of the Soil Corrosion Resistance of Ductile Iron Pipe and
Gray Cast Iron Pipe," Materials Protection, pp. 33 – 36, October.
Simpson, D.M., 2003. Russell Corrosion Consultants, Inc. Letter to Bureau of Reclamation,
June 6.
Smith, W.H., 1968. "Soil Evaluation in Relation to Cast-Iron Pipe," Journal American Water
Works Association, pp. 221 – 227, February.
Smith, W.H., 1972. "Corrosion Prevention with Loose Polyethylene Encasement," Reprinted
from May 1972 Water and Sewage Work.
Smith, W.H., 1973. "Engineering and Construction Practices for Gray and Ductile Cast-Iron
Pipe," Journal American Water Works Association, pp. 788 – 791, December.
Smith, W.H., 1974. "Cast Iron Pipe in Corrosive Environments," Presented at the Tenth
International Water Supply Congress and Exhibition, August.
Spickelmire, B., 2001. "Corrosion Considerations for Ductile Iron Pipe – A Consultant’s
Perspective,” Presented at the NACE International 2001 Western Area Corrosion and
Educational Conference, October.
Spickelmire, B., 2002. "Corrosion Considerations for Ductile Iron Pipe," Materials
Performance, pp. 16 – 23, July.
Standish, J.V. and Leidheiser Jr., H., 1980. "The Electrical Properties of Organic Coatings on
a Local Scale-Relationship to Corrosion," Corrosion – NACE, Vol. 36, No. 8, pp. 390-395,
August.

B – 23

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Staple, M., 2003. Los Angles Department of Water and Power, Personal communication.
Stroud, T.F., 1988. "Forum, Polyethylene Encasement versus Cathodic Protection: A View on
Corrosion Protection," Ductile Iron Pipe Research Association.
Stroud, T.F., 1989. "Corrosion Control Methods for Ductile Iron Pipe," Reprinted from
AWWA’s Waterworld News, Vol. 5, No. 4, July/August.
Szeliga, M.J., 1992. "Corrosion Failures in the Water Industry Case Histories," 1992 AWWA
Distribution System Symposium Proceedings, pp. 219 - 228.
Szeliga, M.J. and Simpson, D.M., 2003. "Underground Corrosion in the Water and Waste
Water Industries." Presented at the Appalachian Underground Corrosion Short Course.
Szoke, N.T. et al., 2001. "Economic Analysis of Watermain Management Options: Cathodic
Protection, 'Hot Spot' Repairs, or Renewal," 2001 American Water Works Association Infrastructure Conference Proceedings.
Szoke, N.T. et al., 2001. "Full-Scale Implementation of Cathodic Protection of Metallic
Watermains," 2001 American Water Works Association - Infrastructure Conference
Proceedings.
V&A Newsletter, 2003. "Assessing DIPRA's New Corrosion Protection Standards."
Infrastructure Preservation News, Vol. 1, No. 2, June (www.vaengr.com).
Vrable, J.B., 1972. "Unbonded Polyethylene Film for Protection of Underground Structures,"
Materials Protection. Vol. 11, No. 3, pp. 26 -28, March.
Wagner, E.F., 1964. "Loose Plastic Film Wrap as Cast-Iron Pipe Protection," Journal
American Water Works Association, Vol. 56, No. 3, pp. 361 – 368, March.
Wakelin, R., 2003. Correng Consulting Service Inc. Letter to Bureau of Reclamation, May 7.
Waters, D.M., 1994. "Demystifying Cathodic Protection," Steel Water Pipe Bulletin No. 1-94,
Steel Plate Fabricators Association, Des Plaines, Illinois.
Webster, R.D., 1993. "Corrosion of Water Distribution and Service Piping Causes and
Solutions," 1993 AWWA Distribution System Symposium Proceedings, pp. 65 - 79.
Whitchurch, D.R. and Hayton, J.G., 1968. "Loose Polyethylene Sleeving for the Protection of
Buried Cast Iron Pipelines," Proceedings of the 1968 Conference on the Corrosion and
Protection of Pipes and Pipelines, pp. 71 - 80.
Woodcock, M., 2003. Washington Suburban Sanitary Commission, Personal communication.

B – 24

Table 1.—Corrosion Prevention Criteria and Requirements
Corrosion Prevention Criteria and Requirements (Updated on April 23, 2003)
Pipe Alternative

External Protection
(primary/supplemental)

Soil Resistivity - 10% probability value
(ohm-m)

Corrosion Monitoring
System

Cathodic Protection
System

Irrigation

M&I

Polyethylene
encasement*

>15
<15

>30
<30

x
x

x

Bonded** dielectric

>10
<10

>20
<20

x
x

x

Mortar/coal-tar epoxy

>25
<25

>50
<50

x
x

x

Mortar

>20
<20

>40
<40

x
x

x

Mortar/coal-tar epoxy

>15
<15

>30
<30

x
x

x

Concrete

>20
<20

>40
<40

x
x

x

Concrete/coal-tar epoxy

>15
<15

>30
<30

x
x

x

Comment [m77]: What is 10% probability
value?

Ductile iron

Prestressed
concrete***

Pretensioned concrete

Reinforced concrete

>40
x
>20
<40
x
<20
>30
x
>15
Steel
Mortar/coal-tar epoxy
<30
x
<15
>10
>20
x
**
Bonded dielectric
<10
<20
x
* Applicable to pipe with corrosion allowance, 24-in inside diameter maximum, and 150 lb/ft maximum.
(NOTE: Given recent pipe industry experience with ductile iron pipe, Reclamation plans to re-examine this provision.)
** Bonded directly to the metal to be protected.
Mortar

*** Reclamation currently has a moratorium on this pipe alternative.

B – 25

x
x
x

Comment [m78]: a note stating "X" indicates
that it is recommended is needed for the table.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figures

Comment [m79]: Appropriate figures would
include: corrosion cell, corrosion at and away from
pinholes in polyethylene, cathodic protection
preventing corrosion, shielding, stray current
corrosion, joint bond, test station.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure 1: Cast iron pipe section prior to sand blasting. Note color and appear
of surface.

B – 27

Comment [gecb80]: Need to place details on
the pipe.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure 2: Same pipe section as shown in Figure 1 after sand blasting. Note
extensive metal loss and the perforation of the pipe wall at three locations. This
example demonstrates the difficulty in visually identifying areas which that
have experienced graphitic corrosion.

B – 28

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Comment [SL81]: Figures 3, 4, and 5 were
added by the Review Panel

Figure 3: Pipe Joint Continuity

B – 29

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure 4: Corrosion Occurring at Breaks in Polyethylene Encasement (Holidays) and Under PE

B – 30

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure 5: Shielding of Cathodic Protection by Polyethylene Encasement

B – 31

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Appendix A

Comment [m82]: If only appendix, A not needed
Comment [m83]: the Appendix is appropriate
and useful.

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Comment [gecb84]: You might want to refer to
AWWA M27 which is the newly updated version of
External Corrosion Control for Water Pipelines. It
give a very complete overview of the subjects.

Corrosion
The Basic Corrosion Cell
Corrosion is the deterioration of a material or its properties due to a reaction with its
environment. This document is limited to the corrosion of metallic materials. Corrosion is a
natural electrochemical reaction, see Figure A-1, between a metal and an electrolyte in which the
refined metal is returned to its natural state as an ore. The following are the four required
components of a corrosion cell:

Comment [m85]: Suggest adding a reference to
Faraday’s Law, in para 3, to support statement
regarding metal loss as a function of current (but I
am not sure if this is the correct page)

1. Anode - The anode is the electrode of the corrosion cell which that experiences the
physical destruction of corrosion (i.e., metal loss). Current (positive or conventional
current) flows from the anode surface into the electrolyte taking metal ions with it.
2. Cathode - The cathode is the electrode of the corrosion cell which that does not
experience the destructive nature of corrosion. Current collects on the cathode surface
from the electrolyte. Because current is collecting on the surface metal ions are not lost.
3. Metallic path - There must be a metallic path between the anode and cathode. Current
flows from the cathode to the anode within the metallic path.
4. Electrolyte - The anode and cathode must be in contact with the same electrolyte.
Current flows from the anode to the cathode within the electrolyte. Ions within the
electrolyte are responsible for the conduction of currents through the electrolyte.
During the corrosion process, current flows between the anode and cathode while chemical
reactions occur at both the anode and cathode surfaces. At the anode current leaves the metal
surface and enters the electrolyte taking metal ions with it, see Figure A-2. The metal ions are a
part of the corrosion products of the corrosion reaction. Rust is the corrosion product of steel.
The current flows through the electrolyte from the anode to the cathode.and collects on the
cathode surface The current then flows through the metallic path and returns to the anode.
Corrosion will cease if one of the four required elements of a corrosion cell is eliminated.
Corrosion is a direct current phenomenon and can be modeled by electrical circuit analysis.
Ohm’s Law (V=IR) (ΔV=ΔIR) is commonly used in analysis of corrosion cells. Ohm’s Law
indicates that there must be a potential (voltage) difference between the anode and cathode for
current to flow between them. Potential differences between anodes and cathodes can be formed
in many ways. In a corrosion cell, the amount of corrosion (metal loss) is directly proportional
to the amount of current flowing. From Ohm’s Law it can be seen that for a given resistance,
larger potential differences result in greater corrosion. Conversely, smaller potential differences
result in less corrosion. For a given voltage, less corrosion occurs in corrosion cells with higher
resistance than those with lower resistance.

B – 33

Comment [m86]: Suggest noting that the
reduction of oxygen is the principal and often ratecontroling cathodic reaction in neutral or alkaline
conditions. This would support the points in the tect
regarding restriction of oxygen to control corrosion

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Anodes and cathodes can be on the same metal surface or they can be on two different metals
which that are in contact with one another. Anodes and cathodes can be atoms apart, they can be
inches apart, or on large structures, such as pipelines, they can be miles apart.
Factors Influencing Corrosion
As indicated above if there is a potential difference between the anode and cathode, corrosion
can occur. There are many factors which that can cause potential differences.
Corrosion of metals can be grouped into two categories: galvanic and stray current. (dissimilar
material couples) and electrolytic (stray current), see Figure A-3. The difference between the two
is the source from which the corrosion current is derived. In galvanic corrosion the source of
current is within the corrosion cell itself, that being the potential difference between the anode
and cathode. For stray current corrosion the source of current is external to the corrosion cell. It
should be noted that the overall result is the same, corrosion occurs at the anode.
Galvanic corrosion cells can be formed by material differences and environmental differences.
One of the most widely recognized galvanic corrosion cell caused by material differences is that
of dissimilar metals. When two different metals are joined and are in contact with a common
electrolyte, one metal will become the anode and the other metal will become the cathode. As a
result of the coupling the corrosion rate of the anodic metal will be accelerated while the
corrosion rate of the cathodic metal will be reduced or eliminated. It should be noted that
dissimilar metals are not the only type of materials differences. Material differences can also
occur on the same metal and can be caused by many conditions, including metallurgical
variables, differences in stress, surface imperfections such as scratches, mill scale on steel, and
etc.
Environmental differences can result in galvanic corrosion. Examples of environment difference
include differences in oxygen concentrations, pH, temperature, soils, velocity and etc. The
oxygen concentration corrosion cell is common. In the oxygen concentration corrosion cell the
surface in contact with the higher dissolved oxygen concentration becomes cathodic to the
surfaces in contact with the lower dissolved oxygen concentration, which becomes anodic. The
anodic areas (lower dissolved oxygen concentration) experience accelerated corrosion as a result
of the oxygen concentration cell. Deposits on a surface, such as mud or sand, can cause an
oxygen concentration cell. The oxygen concentration under the deposit is less than that in the
surrounding electrolyte, resulting in accelerated corrosion occurring under the deposit. Crevices
can also form an oxygen concentration cell, with corrosion occurring in the crevice due to the
lower oxygen concentration being within the crevice as compared to the electrolyte outside of the
crevice.
An important consideration in the analysis of galvanic corrosion cells are is the relative surface
areas of the anode and cathode. As the surface area of the anode decreases in relation to the
surface area of the cathode, the intensity of corrosion on the anode surface increases. This
B – 34

Comment [m87]: velocity of what?

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

results from an increase in current density discharging from the anode surface. No matter what
condition has initiated the corrosion cell, if the anodic area is relatively small with respect to the
cathodic area, corrosion will tend to be intense. If, on the other hand, the anodic area is large as
compared to the cathodic area, corrosion will be relatively mild.
Polarization of a corrosion cell is an important factor which that controls the rate of corrosion.
The anodic and cathodic reactions result in products being formed on the surfaces of the anodes
and cathodes. Corrosion in neutral and near-neutral electrolytes results in formation of a
hydrogen film on cathode surfaces. The hydrogen film can act as an insulating barrier. Current
flow through this insulting film provides a voltage drop across the film which that is in
opposition to the original driving voltage of the corrosion cell. The overall effect of the voltage
drop is a reduction in the driving voltage of the corrosion cell, which in turn, results in less
current flow and, therefore, less corrosion. This process is known as polarization and reduces the
amount of corrosion occurring. Anything that disrupts the polarization film (depolarization)
increases the corrosion rate. Depolarization can occur from mechanical and/or chemical means.
Water flow can strip polarization films from anode and cathode surfaces. Dissolved oxygen
within an electrolyte can be a major factor in depolarization, the depolarization. When oxygen
combines with the hydrogen and when it does it is breaking to form water, it breaks down the
hydrogen film.
In neutral or near-neutral environments, oxygen and moisture are required for corrosion. From a
corrosion standpoint, soil is a neutral or near-neutral environment. Therefore, oxygen has an
important role in corrosion by soils.
Two prominent factors affecting corrosion in soils are the soil resistivity and aeration. Soil
resistivity has an impact on the overall circuit resistance of the corrosion cell. A decrease in soil
resistivity generally results in a decrease of the overall circuit resistance. According to Ohm’s
Law as the circuit resistance decreases the current flow increases (assuming a constant voltage).
Therefore, soils with lower resistivities are generally more corrosive than soils with higher
resistivities. Aeration affects corrosion by promotion of oxygen concentration cells.
Stray current corrosion or interference results from the unintentional collection of current on a
structure from a foreign power source. The collected current must return to the source from
which it originated and to do so it must leave the structure on which it collected. Accelerated
corrosion is experienced on the surface of the structure where the stray current discharges from
the structure into the electrolyte on its return to the originating source.
Microbiologically influenced corrosion occurs as a result of the metabolic process of
microorganisms. They can influence corrosion by promoting concentration cells, creating
corrosive conditions, and behaving as cathodic and anodic depolarizers. A common form of
micro-biologically influenced corrosion involves sulfate-reducing bacteria. Sulfate-reducing
bacteria require an anaerobic environment which that includes sulfates and hydrogen. A source

B – 35

Comment [m88]: Actually, oxygen is the
cathodic reduction reaction that supports the anodic
oxidation reaction. If there is no oxygen in a neutral
solution, there is no corrosion. A potential
difference will exist, but since the reduction reaction
is gone, there can not be any further oxidation.
Comment [m89]: Typically an impressed current
cathodic protection system on an adjacent pipeline or
structure

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

of hydrogen for their metabolic process can be cathodic surfaces and, thus, they can act as a
cathodic depolarizer. In addition, a by-product of their metabolism, hydrogen sulfide, is a
corrosive substance.
When corrosion related corrosion-related leaks occur on a given pipeline system, the leak data
can be used to predict the number of future leaks. It has been shown that the frequency of
corrosion related corrosion-related leaks increases logarithmically and when the accumulated
exponentially and when the cumulative leaks versus time is plotted on a semi logarithmic graph
paper the resulting plot will tend to be a straight line. Corrosion related Corrosion-related
failures tend not to be a single occurrence and as additional failures occur they occur more
rapidly.
Corrosion Mitigation
Corrosion Monitoring Systems
A corrosion monitoring system allows for testing of the pipeline without excavation and is used
in the application of cathodic protection to the pipeline should the need arise. The basic
corrosion monitoring system provides electronic access to the pipeline, electrical continuity of
the pipeline, and electrical isolation of the pipeline from appurtenances, see Figure A-4.
Electronic access to the pipeline is provided by test stations in which insulted electrical cables
originating from the pipeline terminate. Test stations are installed at critical locations and at
regular intervals along a pipeline. Positive electrical continuity is provided by welded pipe joints
or installation of joint bonds across mechanical type pipe joints (flanges, bell and spigot joints,
dresser couplings, and etc.). The pipeline is electrically isolated as necessary from
appurtenances by the installation of insulated fittings.
Protective Coatings
Protective coatings are widely used for corrosion protection. Selection of protective coatings is
highly dependent on environment conditions. This discussion will be limited to protective
coatings for buried pipeline applications. Coatings for buried pipelines can be divided into two
categories, those with relatively high electrical resistance and those with relatively low electrical
resistance. Low resistance coatings include mortar coatings and concrete encasements, and are
not included in this report. For this report the term dielectric coating will be used to describe the
relatively high resistance type coating. Bonded dielectric coatings are designed to tightly adhere
to the metallic surface and have a high electrical resistance. The principal corrosion protection
mechanism of a bonded dielectric coating is to provide a physical barrier between the corrosive
environment and the underlying metallic surface. In addition, a bonded dielectric coating
protects the underlying metallic surfaces by increasing the effective circuit resistance of the
corrosion cell, which in turn reduces the current flow within the corrosion cell in accordance
with Ohm’s Law. Because there are no perfect coatings there are always locations where there
are discontinuities in the coating, these discontinuities which are generally called holidays.
B – 36

Comment [gecb90]: Reference is Peabody
Pipeline Corrosion Control

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Holidays expose the underlying metallic surface directly to the corrosive environment. Contrary
to common belief, dielectric coatings typically used on buried pipelines are not perfect insulators
and, therefore, can conduct current. Moisture and oxygen can also diffuse through coatings.
The rate at which current, moisture, and oxygen can move through a coating is dependent on the
coating characteristics (e.g., resistivity and thickness), environmental conditions, and time. Once
a protective coating is placed into service it begins to absorb moisture, which in turn reduces its
effective resistivity over time.
Because dielectric coatings are capable of conducting current, the surface beneath intact
dielectric coating is available to behave anodically or cathodically. Studies have indicated that
metallic surfaces under intact bonded dielectric coatings are cathodic to the metallic surfaces
exposed at the coating holidays, which are anodic. The severity of this corrosion cell is
dependent on both coating and soil properties.
All coatings deteriorate with as time, and as they do, their ability to provide corrosion protection
also deteriorates.
Although protective coatings are a very useful and effective tool in corrosion mitigation of
buried pipelines, they do not eliminate corrosion of the pipeline. As a result, cathodic protection
is often used on buried pipelines, this pipelines. This is especially true for pipelines in corrosive
soils.
Cathodic Protection
Cathodic protection is a proven method of mitigating corrosion and is the only corrosion control
method, which can potentially halt ongoing corrosion of a buried structure. Cathodic protection
uses a corrosion cell to the benefit of the protected structure. With cathodic protection the
structure that is to be protected is made the cathode of the corrosion cell (corrosion does not
occur at the cathode). Since we still have an operating corrosion cell we must have an anode.
Therefore, an anode material must be installed, which will be sacrificed for the sake of the
structure to be protected. It should be noted that corrosion is not stopped but is transferred. It is
transferred from the structure that is to be protected to sacrificial material, which is installed to
be consumed.
Since cathodic protection is a corrosion cell, current must flow. As with the corrosion cell,
current flows from the anode to the cathode within the electrolyte, and from the cathode to the
anode within the metallic path. For pipeline installations the electrolyte is the surrounding soil.
The metallic path is the pipeline itself and the cables that may be installed with the cathodic
protection system. A pipeline must be electrically continuous for the successful application of
cathodic protection; therefore, a corrosion monitoring system is required on a cathodically
protected pipeline.

B – 37

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

There are two types of cathodic protection systems, galvanic anode and impressed current. Both
systems require the installation of a sacrificial material as the anode. Galvanic anode cathodic
protection requires the installation of galvanic anodes. A galvanic anode is a material which that
is more electro-chemically active than the structure to be protected, see Figure A-5. Galvanic
anodes use the natural potential difference between the anode material and the structure to cause
current to flow. For soil applications zinc and magnesium are typically used as the galvanic
anode material. Galvanic anodes are typically installed some distance from a pipeline and
connected to the pipeline through cables.
With an impressed current cathodic protection system, external power is required to supply the
current required for cathodic protection, see Figure A-6. Any DC type power supply can be used
for cathodic protection, although, a rectifier is typically used. A rectifier converts AC power into
DC power. The positive terminal of the DC power supply is connected to the anodes, and the
negative terminal is connected to the pipeline. Impressed current requires the installation of
anodes and a power supply, the power supply is connected between the structure and anodes.
Because external power is providing the driving force for the cathodic protection current, a wide
range of anode materials can be used. Some commonly used impressed current anode materials
include high silicon cast iron, graphite, mixed metal oxides, and platinum.
The cathodic protection system must be capable of supplying sufficient current to provide
adequate cathodic protection. Galvanic anode cathodic protection systems are limited in the
current which that they can provide and therefore are typically used in situations with small
current requirements (e.g., smaller pipelines or well coated pipelines). Impressed current
cathodic protection systems can provide a large and variable amount of current and can be used
in situations requiring small or large current requirements (e.g., larger pipelines or poorly coated
pipelines).
Synergistic Effects of Protective Coatings and Cathodic Protection
Protective coatings and cathodic protection are widely used as synergistic corrosion mitigation
methods. There are no perfect coatings; they have holidays, can be damaged, and deteriorate
with time. The metal exposed at the coating holidays is susceptible to corrosion. The corrosion
process enlarges the coating defects by undercutting the intact coating adjacent to the holidays.
Coatings effectively reduce the amount of metal surface area which requires cathodic protection
and as a result less cathodic protection current is required for a well coated well-coated structure
than for a poorly coated or bare structure. In return, cathodic protection extends the useful life of
the coating by reducing undercutting of the coating and effectively limiting the growth of
defective coating areas.

B – 38

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Comment [SL91]: Figures A-1 through A-6 were
added by the Review Panel

Figure A-1 – The Electrochemical Corrosion Cell.

B – 39

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure A-2 – Basic Corrosion Cell with a buried pipe.

B – 40

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure A-3 – Corrosion due to stray current.

B – 41

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure A-4 – Corrosion Monitoring System.

B – 42

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Figure A-5 – Galvanic Anode.

Figure A-6 – Impressed current Cathodic Protection System.

B – 43

Appendix B
“DRAFT – Considerations in Using Polyethylene Encasement with Ductile Iron Pipe”

Page B-2 [1] Comment
(continued) if to date there has not been a reported corrosion failure of any ductile iron pipeline
on a Reclamation designed project or on a project for which Reclamation has had an oversight
responsibility. Then what is the concern for corrosion damage? Something needs to be
described here for justification for the concern. I thought the materials on page 8 under
Discussion touch this issue, but they need to be expanded and moved up here. Although no
failures have been reported, failures in other areas have been cited. So, there are possibilities that
corrosion of ductile iron pipes with BOR’s designs or under BOR’s oversight might occur. It also
might be important to state that the cost of a failure will be enormous. Along the same line, it is
worthwhile to estimate the failure probability of ductile iron pipes due to corrosion. This is might
be complicated due to many factors involved, such as the pipe dimension, soil properties and
environment, etc. But it can be done on assumed realistic conditions.

Page B-11 [2] Comment
(continued) Suggest considering the positions of the Europeans and other international groups on
the issue. He states that it is his understanding that polyethylene encasement has not been
accepted as the sole form of protection for ductile iron in Europe. Also consider noting that in
the U.S., the situation with respect to polyethylene encasement seems to have resulted in the
evolution of 3 camps: (1) those outright rejecting polyethylene encasement and treating of
ductile iron pipe the same as steel pipe, (2) those completely accepting polyethylene encasement,
and (3) those somewhere between these two positions. This would seem to reinforce the
conservative position recommended by Reclamation, namely, limiting the use of polyethylene
encasement until research answers the fundamental questions posed in the Recommendations
section.

B – 44

Appendix C
E-Mail Messages from Mike Woodcock to James Keith

Appendix C
E-Mail Messages from Mike Woodcock (Washington Suburban)
to James Keith (Reclamation) 3/11/04
Mike Woodcock works for Washington Suburban as a metallurgist. The following are excerpts
from several E-mail messages:
James,
The Commision has some steel pipe most are only 10 years old+/-, these were
tape coated and cathodically protected. The oldest is 30 inch at least 50
years probably 60 years with little maintenance history, no CP, and was Coal
Enamel Tar Coated. We have experienced a few pin hole leaks which were
fairly easy to patch/repair. It has straight lengths of pipe with couplings.
We have had some leaks on near the couplings usually because of damage in
the original coating.
I suggest you look at steel pipeline lives in oil and gas country where many
steel pipelines are over 100 years old.
All but the aboved mentioned pipeline are welded, cement lined, tape coated
with CP are large diameter,36-96 inch and fairly recent(10-15 years).
Mike Woodcock,
WSSC Systems Infrastructure Group.
-----Original Message----From: James Keith [mailto:JKEITH@do.usbr.gov]
Sent: Thursday, March 11, 2004 1:12 PM
To: lleahy@wsscwater.com; Mwoodco@wsscwater.com
Subject: Re: FW: DIP life query from Corps Engineers ref your telcon
query yesterday
Lori and Mike,
Thanks for the info on ductile iron. Does Washington Suburban have any
experience/info on the service life for steel pipe?
>>> "Leahy, Loretta" 03/11/04 10:48AM >>>
fyi
Lori Leahy
WSSC Systems Inspection Group Leader
office-301 2068039
cell-301 7850116
fax- 301 2068860
lleahy@wsscwater.com
> -----Original Message----> From: Woodcock, Mike
> Sent: Thursday, March 11, 2004 12:13 PM
> To:
Leahy, Loretta
> Cc:
Debevoise, Ana
> Subject:
DIP life query from Corps Engineers ref your telcon
query

C–1

Appendix C
E-Mail Messages from Mike Woodcock to James Keith

> yesetrday
>
> Lorie, you can get the engineer to call me direct. This is a very
> complicated query to answer and needs background justification for
values
> given
> The following are Mike Woodcock's (Metallurgist/ Systems
Infrastructure)
> predictions. DIP in WSSC is too young to have established lives but
trends
> are developing.
>
> Theoretical Life unwrapped DIP - pit penetration start after 25
years
> -useful life 35 years (Howard County MD currently replacing
unwrapped
> 20-25 year old DIP and we are just beginning to see Pitting
failures.
> Failure mode/trend will be an increasing frequency of pitting leaks
until
> pipelines become sprinkler systems.
>
> Theoretical Prediction ranges from to 40-45 years for Polyethylene
> encased pipe--- pits at some locations (dependant on soil, damage to
wrap,
> copper service line connections, acid ground water etc) life
dependant on
> frequency of maintenance required.
>
> To get 100 year life follow European practices -zinc/aluminum
metallic
> spray coat, epoxy top coat plus polyethylene encasement.
> or blast clean off magnetite coating- coat with either fusion bond
epoxy
> (not currently available), or coat with extruded polyethylene
coating
> system then add CP ---100 years
>
> Remember to get pipeline long life also requires long life for
fittings,
> and appertnances-- currently low life components.
>
> Recommend review work done by NRC-NRC Canada Dr. Balvant Rajani
>
> DC Local water utilities have recently formed a regional forum on
DIP to
> challenge DIP industry marketing policies, product qa/qc, coating
> questions, and pressure classes.
>
> Never use bell and spigot steel pipe.( too thin--- difficult to
corrosion
> protect---- danger in long term of stress failures in shoulders of
pipe
> ends rolled joints)
>
> Mike Woodcock
> Mwoodco@wsscwater.com
> 301-206-8572

****************************
James,
The terminology you use "breaks/mile/year" should strictly not be used for

C–2

Appendix C
E-Mail Messages from Mike Woodcock to James Keith

DIP. This terminology was created for CIP cast iron pipe (&PCCP) which fail
by brittle fracture and the pipe splits into two sections. Only DIP with low
notch toughness and brittle should fail this way (poor manufacturing). DIP
by definition should not break,but splits open when extensive pits join in a
straight line yes. The failure mechanism for DIP is pitting failures. Please
remember DIP is very young when compared to CIP and theorectically DIP as
expected by us is only just beginning to show signs of distress in WSSC
area, i.e pitting failures and some splits. The oldest WSSC DIP is in the
order of 27 years old we expect to see increasing events from from now on.
my estimate was by age 35 we should see alot of events.The Commission has
approximately 2000 miles of DIP 3-54 inch diameter. Most was installed
without polyethylene encasement. some is now showing signs of severe
pitting. 36 inch and above was blast cleaned and either epoxy or tape coated
and CP was applied. Because we have such a high quantity of DIP maintenance
events per mile per year is not very large,at this time, my guessimate is
in order of .025 for 2001-2002 and for 1997 was or order of
0.0003/mile/year. For comparision our 2003 CIP rate was approx. 0.617
breaks/mile/year
I suggest you talk to Don Lieu at Howard County(Howard county adjoins our
service to the north of us and their pipe is a little older). 410-313-6121
Dlieu@co.ho.md.us
mike w
-----Original Message----From: James Keith [mailto:JKEITH@do.usbr.gov]
Sent: Friday, March 12, 2004 7:41 PM
To: mWoodco@wsscwater.com
Subject: RE: FW: DIP life query from Corps Engineers ref your telcon
queryyesterday
Mike,
What is Washington Suburban's figure for breaks/mile/yr for ductile
iron? Thanks
>>> "Woodcock, Mike" 03/11/04 12:16PM >>>
James,
The Commision has some steel pipe most are only 10 years old+/-, these
were
tape coated and cathodically protected. The oldest is 30 inch at least
50
years probably 60 years with little maintenance history, no CP, and was
Coal
Enamel Tar Coated. We have experienced a few pin hole leaks which were
fairly easy to patch/repair. It has straight lengths of pipe with
couplings.
We have had some leaks on near the couplings usually because of damage
in
the original coating.
I suggest you look at steel pipeline lives in oil and gas country where
many
steel pipelines are over 100 years old.
All but the aboved mentioned pipeline are welded, cement lined, tape
coated
with CP are large diameter,36-96 inch and fairly recent(10-15 years).
Mike Woodcock,
WSSC Systems Infrastructure Group.
-----Original Message-----

C–3

Appendix C
E-Mail Messages from Mike Woodcock to James Keith

From: James Keith [mailto:JKEITH@do.usbr.gov]
Sent: Thursday, March 11, 2004 1:12 PM
To: lleahy@wsscwater.com; Mwoodco@wsscwater.com
Subject: Re: FW: DIP life query from Corps Engineers ref your telcon
query yesterday
Lori and Mike,
Thanks for the info on ductile iron. Does Washington Suburban have
any
experience/info on the service life for steel pipe?
>>> "Leahy, Loretta" 03/11/04 10:48AM >>>
fyi
Lori Leahy
WSSC Systems Inspection Group Leader
office-301 2068039
cell-301 7850116
fax- 301 2068860
lleahy@wsscwater.com
> -----Original Message----> From: Woodcock, Mike
> Sent: Thursday, March 11, 2004 12:13 PM
> To:
Leahy, Loretta
> Cc:
Debevoise, Ana
> Subject:
DIP life query from Corps Engineers ref your telcon
query
> yesetrday
>
> Lorie, you can get the engineer to call me direct. This is a very
> complicated query to answer and needs background justification for
values
> given
> The following are Mike Woodcock's (Metallurgist/ Systems
Infrastructure)
> predictions. DIP in WSSC is too young to have established lives but
trends
> are developing.
>
> Theoretical Life unwrapped DIP - pit penetration start after 25
years
> -useful life 35 years (Howard County MD currently replacing
unwrapped
> 20-25 year old DIP and we are just beginning to see Pitting
failures.
> Failure mode/trend will be an increasing frequency of pitting leaks
until
> pipelines become sprinkler systems.
>
> Theoretical Prediction ranges from to 40-45 years for Polyethylene
> encased pipe--- pits at some locations (dependant on soil, damage to
wrap,
> copper service line connections, acid ground water etc) life
dependant on
> frequency of maintenance required.
>
> To get 100 year life follow European practices -zinc/aluminum
metallic

C–4

Appendix C
E-Mail Messages from Mike Woodcock to James Keith

> spray coat, epoxy top coat plus polyethylene encasement.
> or blast clean off magnetite coating- coat with either fusion bond
epoxy
> (not currently available), or coat with extruded polyethylene
coating
> system then add CP ---100 years
>
> Remember to get pipeline long life also requires long life for
fittings,
> and appertnances-- currently low life components.
>
> Recommend review work done by NRC-NRC Canada Dr. Balvant Rajani
>
> DC Local water utilities have recently formed a regional forum on
DIP to
> challenge DIP industry marketing policies, product qa/qc, coating
> questions, and pressure classes.
>
> Never use bell and spigot steel pipe.( too thin--- difficult to
corrosion
> protect---- danger in long term of stress failures in shoulders of
pipe
> ends rolled joints)
>
> Mike Woodcock
> Mwoodco@wsscwater.com
> 301-206-8572

C–5

Appendix D
Questions for the Panel and Panel Conclusions

Appendix D
A review panel was convened by Reclamation in March of 2004 to peer review Reclamation’s
evaluation of the effectiveness of unbonded coatings on metallic pipe. The panel consisted of
three materials scientists from the National Institute of Standards and Technology (NIST)
(C.N. McCowan (Panel Chair) and Y. Cheng, Materials Reliability Division, Boulder, CO; and
R.E. Ricker, Metallurgy Division, Gaithersburg, MD) and two private sector corrosion engineers
(G.E.C. Bell, M.J. Schiff & Associates, Claremont, CA; and R.Z. Jackson, CH2M Hill,
Sacramento, CA.

Questions for the Panel and Panel Conclusions
1. Reclamation currently requires protection on pipe alternatives (i.e., no bare pipe is
installed) should problems be encountered in the future due to either environmental
corrosion or stray current.
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?
JacksonConcurred

BellConcurred, but noted that cost is a consideration. He said coatings should
be used for costs up to $3/ft2, because cathodic protection can be applied
for about this cost.

ChengConcurred
2. Reclamation currently requires bonded joints and Corrosion Monitoring for all
pipeline installations in order to monitor and assess pipe corrosion activity.
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?
D–1

Appendix D
Questions for the Panel and Panel Conclusions

JacksonConcurred; but said one should allow for exceptions.
He said that in special cases where there are stray currents one should
consider isolation rather than conductivity. For example, he worked on a
project where a pipeline paralleled a high voltage power line. In that
situation, isolation from other structures is definitely needed, and can be
achieved by reducing the continuous length of pipe that can draw a stray
current.

Bell–
Concurred that bonded joints and test stations are needed, and that
isolation from other structures is important. He also stated that with a
bonded coating, one may not be able to see changes in the potentials on
the pipeline, meaning it may be difficult to detect if corrosion is occurring.
He felt that newer technologies, such as electrical resistance coupons, may
be better.

ChengConcurred with the practice of corrosion monitoring. He also stated that
one needs to monitor for unusual circumstances and changes in potential,
and have a practice or written guideline to establish what changes to look
for and what to do if changes are found.

Other comments:
Connections from sublaterals to main pipeline account for 90 percent of
all corrosion problems on distribution systems. Isolation is the key.
Cathodic protection is the last resort if there are problems.
3. Reclamation currently uses soil resistivity and stray current as an indicator of need
for CP. Additionally, in some cases Reclamation will examine chlorides and sulfates
concentrations in the soil. This approach does not consider, or may be considered to

D–2

Appendix D
Questions for the Panel and Panel Conclusions

assume, other parameters of soil chemistry, pH, Oxidation Reduction Potential
(Redox), cyclic wetting and drying (moisture), etc. This parameter is quick, easy
and cheap to measure in the field.
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?
JacksonHe stated that field resistivity is one part of the data gathering. CH2M Hill
prefers the collection of additional information for major pipelines, e.g.,
pH, chlorides, and sulfates. Resistivity values are calculated in the
laboratory (saturated) as well as in the field. He stated that the potential
for stray currents needed to be evaluated, and that a conservative
assumption would be that every project is likely to have stray current. The
use of PE encasement to provide shielding from stray currents is a good
idea.

BellHe felt the best approach was to get the pipe in the ground and then
determine what is needed. He stated that even hazardous pipelines are
given 1 year of operation to allow for tweaking of CP to meet exact needs
of a particular pipeline.
He stated that resistivity is a good indicator of corrosion mitigation needs,
but that the use of Electro-Magnetic Conductivity Surveys may be better.
Measurements could be taken every 20 feet to 15 feet of depth. This
method should be used to find where there are changes, and that data
should be used to determine the field sampling locations. He stated that
the anions–chlorides and sulfides—as well as the cations—calcium,
magnesium, and sodium need to be measured. He felt that there is a small
price difference between a full analysis and a partial analysis, and that this
extra analysis helps determine where to put magnesium beds.

Other comments:
A conservative assumption would be to use good coatings and CP for
lower resistivity soils.

D–3

Appendix D
Questions for the Panel and Panel Conclusions

Stray current is difficult to assess. The conservative view is to assume
projects are likely to have future potential for stray current.
4. PE effectiveness is a disputed issue both for its ability to protect pipe from
corrosion, possible installation damage and potential shielding which impacts
Corrosion Monitoring and CP. For example, NACE International’s RPO 169-2002
“Control of External Corrosion on Underground or Submerged Metallic Piping
Systems,” requires a bonded dielectric coating for buried pipeline applications and
indicates that unbonded coatings (PE encasement is considered an unbonded
coating) can create electrical shielding of the pipeline that could jeopardize the
effectiveness of the CP system. Reclamation is concerned by this dispute.
Does the panel have comments with regard to the effectiveness of PE
encasement as a corrosion measure and/or its effect on the ability to monitor
pipe corrosion and to apply effective CP?
JacksonHe felt that PE encasement is not a perfect answer, but there are locations
in less corrosive environments where it can be used. He agreed that
Reclamation has a legitimate concern and needs to take a conservative
view, and should make changes to corrosion mitigation criteria if
warranted.
He has used PE encasement with CP, and has not had any cases where he
has been called to go back and inspect the pipe. This would indicate that
there have been no specific problems for these cases.
He said that two other aspects should be considered:
1. As the pressure class decreases, the pipe thickness decreases,
making the thinner pipe more susceptible to penetration. The pipe
thickness also decreases as the size decreases.
2. Bedding and backfill are critical and must be considered carefully.
CH2M Hill likes to use sand as a bedding material for DIP with PE. A
minus ¼” gravel may be reasonable. Dig-ups have shown damage to
the PE, especially around the top of the pipe. Two layers of PE
encasement could help eliminate this problem.
CH2M Hill is more conservative with larger diameter pipe because the
flows are larger, the implications of the failure are greater, and large

D–4

Appendix D
Questions for the Panel and Panel Conclusions

diameters are more expensive to fix. With larger pipe, a more
conservative approach is warranted. With 12-inch and smaller pipe, less
conservatism may be needed.

BellHe stated that he leans towards the use of PE encasement with CP applied,
because he has seen it work. He agreed that PE encasement cannot be
considered to be a coating; it is an encasement only. He said that data has
recently been published which indicates DIP with a select backfill can be
protected with PE encasement to reduce corrosion, and that CP works
under intact PE.
He noted that RP0169 (RP stands for Recommended Practice)
recommends a tight bonded coating, but that it is not a requirement; it is
only a recommended practice. He stated that he has never specified tight
bonded coating with DIP.
He stated that he has had good experience with PE encasement and with
the application of CP on polyethylene encased DIP. He stated that the
costs of PE encasement are on the order of $0.05/diameter inch of pipe.
He also stated that the cost of CP for DIP with PE encasement can be
considered to be 28 times that of steel, but that it is still a small number
when put in context of the entire project cost.
He advised Reclamation to look at its own experience. He stated that if
Reclamation has not had failures with PE encasement, then it should keep
doing what has been done. He said that he has never seen significant
failures of DIP protected with PE encasement and CP.
He said that damage to the PE encasement is not due to the weight or size
of the pipe, but the fact that the wrong type of PE encasement is used. He
stated that the quality of PE encasement can vary greatly, and that lowerquality PE may not have enough thickness or tensile strength.
He felt that the size restriction on pipe with PE encasement should be
eliminated. He agreed that the consequences of failure need to be
considered. Larger diameter pipe generally does have higher
consequences.

D–5

Appendix D
Questions for the Panel and Panel Conclusions

He stated that the fittings on the pipe cause the most problems, because the
pipe is manufactured in a controlled environment, whereas the fittings are
a field installation and not controlled as well. He felt that close inspection
during installation is the best investment.

Other comments:
The quality of the PE is important.
Inspections and cathodic system maintenance are important.
5. Reclamation is prepared to recommend an updated approach for pipe alternative
coatings or encasements installed in various soil conditions. The newest
recommendation is enclosed as Table 2.
Does the Panel concur with the Table?
Does the panel have comments with regard to the Table?
BellHe stated that a bonded dielectric coating is more difficult to apply and
more expensive for DIP than for steel pipe. With DIP, a thicker coating is
needed due to the dimpling on the pipe, and that the larger the diameter,
the greater the coating thickness becomes. Thick coatings can cause
problems at the joints, making the pipe hard to assemble. Mortar and
reinforced concrete need to be handled differently. Mortar coating in
conditions with chlorides and sulfides is a problem. In wetting and drying
conditions, the mortar can act like a sponge, and eventually lead to
chlorides accumulating on the metal. Corrosion protection additives can
be put into the coating. If coal tar epoxy is used, it should be used directly
on the steel, with mortar on the outside for rock protection. He stated that
three layers of tape with mortar coating are pretty much bullet proof. He
said that a seal coat over mortar is not a good system, because it could
cause shielding of CP and allow corrosion to occur under any disbonded
mortar coating. The mortar should be used over the dielectric coating.
He said that both coal tar epoxy and PE encasement can shield CP.
He said that for soil resistivities below 1,500 Ohm-cm, PE encasement
with CP should be used.

D–6

Appendix D
Questions for the Panel and Panel Conclusions

He stated that the Reclamation table is geared towards conservatism, and
that this makes sense if it agrees with a good history of installation.
He stated that if CP systems are not always well maintained, one should
never depend totally on CP to protect a pipeline.

JacksonHe stated that if a bonded dielectric coating is required, alternatives will
probably be more limited, because pipe will probably not be obtainable
from DIP manufacturers. He said that it is a good idea to make sure there
is more than one pipe alternative available in order to keep capital costs
down.
He felt that there could be problems with corrosion in any soils with
resistivities below 3,000 Ohm-cm. For resistivities below 2,000, he felt
that corrosion protection designs should definitely be considered. For
resistivities below 1,000, he felt that there could be really serious
problems.
In the end, he felt that the user should adhere to the criteria with which
they are the most comfortable.

Other comments:
Coal tar epoxy can be placed directly on the pipe with mortar over the
epoxy for rock protection.
If the coal tar epoxy is on the outside of the mortar and the mortar
becomes disbonded from the pipe, salty water can be a problem.
6. Pipe life cycle costs, or other economic considerations are important in the overall
design and O&M budgeting and expenditures over the life of a project.
Reclamation is prepared to use pipe life cycle costs as a bid correction item.
Does the Panel concur with this practice?
Does the panel have comments with regard to this practice?

D–7

Appendix D
Questions for the Panel and Panel Conclusions

JacksonIn general, he felt that life cycle costs are needed in specifications. He
concurred with using bid adjustments in specifications for increased costs
due to CP. As an example, CH2M Hill did use long-term costs for the
Mni Wiconi Project, but it did not change the pipe option selected for the
project. The lowest life cycle costs were for DIP with PE encasement and
CP.

BellHe said he has never used life cycle costs, but he would have no problem
with including it. He stated that it would be important to be definitive
about how the calculation will be made.
He said that, in general, the cost of installation of CP is about $2,000 to
$3,000 per installed amp. The current required for ductile iron is about
28 to 30 times that required for steel.
He felt that the average service life for a pipe project should be assumed to
be 40-60 years, so a good starting point would be 50 years. He has known
clients that have asked for as high as 100 years.

D–8

Appendix E
Exterior Coating Cost Analysis

Appendix E
Exterior Coating Cost Analysis
Exterior Coating Cost Analysis
Unit Price per SF
Ductile Iron Pipe Study
Daniel L. Maag
Tuesday, April 06, 2004

Pipe Diameter (Inches)

2
2.5
3
4
6
8
10
12
14
16
18
20
24
26
28
30
32
34
36
40
42
48
Average Price Per SF

8-mil Poly 3/4" Mortar
Tubes (F&I)
Coating
Price/SF
Price/SF
$/SF
$/SF

$1.40
$1.10
$0.80
$0.70
$1.30
$1.10
$1.20
$1.10
$1.10
$1.00
$1.00

$5.30
$4.50
$3.50
$3.40
$3.40
$3.10
$3.20
$3.10
$3.10
$3.10

$1.00

$0.90

$1.10

$3.60

Pipe
Wrapping
Price/SF
$/SF
$2.30
$2.00
$1.80
$1.70
$1.80
$2.00
$2.10
$2.10
$2.30
$2.50
$2.60
$2.70
$2.80
$3.10
$3.20
$3.30
$3.50
$3.60
$3.60
$3.90
$4.00
$4.30
$2.80

NOTES:
1. The unit prices for poly tube include a cost component for installation of tube on pipe section.
2. The unit prices for mortar coating and pipe wrapping include cost for installation on pipe section.
3. For internal mortar lining, Richardsons noted that for quantities less than 200 lf, add 40 percent to the above costs.
4. For internal mortar lining, Richardsons noted that for quantities greater than 500 lf, deduct 25 percent from the above costs.
5. For external mortar coating, Richardsons noted that for quantities less than 200 lf, add 30 percent to the above costs.
6. For external mortar coating, Richardsons noted that for quantities greater than 500 lf, deduct 40 percent from the above costs.
7. Nominal pipe diameters were used to calculate these costs per square foot.
8. Average prices per square foot (above) are based on mathematical averages of all diameters for each option (column).

E–1

Appendix F
April 2004 Southwest Pipeline Excavation

Appendix F
April 2004 Southwest Pipeline Excavation
The Southwest pipeline project is a water supply system designed to deliver water from
Lake Sakakawea on the Missouri river to municipalities and rural communities located in
southwestern North Dakota. The Southwest Pipeline is a Reclamation funded project which was
installed in1989. The pipeline was constructed with ductile iron pipe with joint bonding and PE
encasement. In 1991, cathodic protection was implemented on the pipeline. Testing conducted
in late 1997 and early 1998 indicated low protective potentials in a low-lying area near Taylor,
ND. In April 2004, several PE encased ductile iron pipe units were excavated on the Southwest
pipeline (See Figure 1). Two excavations were performed approximately 50-ft apart. The first
excavation was performed at Sta. 239+30 and the second excavation at Sta. 239+84. Water was
encountered in both excavations. The water was entering the trench from a coal seam along the
trench wall. The excavated ductile iron pipe diameter was approximately 30 inches.

Figure 1—Excavated 30-inch diameter Southwest pipe unit
with PE encasement

F–1

Appendix F
April 2004 Southwest Pipeline Excavation

A third excavation site near the location of a rectifier station (approximately Sta. 200+00) was
attempted. However, the third excavation site could not be completed due to water flow into the
pipe trench. The pumps provided for the dewatering effort could not keep up with the inflow of
water.
Reclamation representatives from the Technical Service Center and Dakotas Area Office were
present during the inspection. Sections of the PE encasement were removed from the ductile
iron pipe units including underneath the ductile iron pipe unit. The overall condition of the
excavated ductile iron pipe unit was visually observed to be good. Surface corrosion was noted
on the excavated ductile iron pipe underneath the PE encasement (See Figure 2). Corrosion
pitting or graphitization was not visually observed.

Figure 2—Surface corrosion noted underneath PE encasement

A section of the PE encasement was removed and visually inspected. Visual inspection of the
PE encasement located underneath the pipe unit (invert) indicated numerous perforations likely
due to the pipe bedding material used. The pipe bedding consisted of angular material which
likely resulted in development of numerous perforations in the PE encasement. A section of the
PE encasement which was located underneath the pipe unit is shown in Figure 3.

F–2

Appendix F
April 2004 Southwest Pipeline Excavation

Figure 3.—PE encasement with numerous perforations.

Figure 4 provides a close-up which illustrates with greater detail the numerous perforations
visually observed on the PE encasement shown in Figure 3. The numerous perforations in the
PE encasement are likely the cause of the very high currents required to achieve the required
protective potentials in this area.

Figure 4.—Close up view of PE encasement with
numerous perforations.

F–3