NBSIR 74-435

Progress Report on the Performance

I of Bituminous Coated Cast-Iron

Pressure Pipe Buried in Various

Soil Environments for Four Years

W. F. Gerhold and B. T. Sanderson

Corrosion and Electrodeposition Section

IVIetallurgy Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

January 1974

Progress Report

Prepared for

Tri Services

Department of the Navy

Naval Facilities Engineering Command

Washington, D. C. 20390

NBSIR 74-435

PROGRESS REPORT ON THE PERFORMANCE

OF BITUMINOUS COATED CAST-IRON

PRESSURE PIPE BURIED IN VARIOUS

SOIL ENVIRONMENTS FOR FOUR YEARS

W. F. Gerhold and B. T. Sanderson

Corrosion and Electrodeposition Section

Metallurgy Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

January 1974

Progress Report

Prepared for Tri Services

Department of the Navy

Naval Facilities Engineering Command

Washington, D. C. 20390

U. S. DEPARTMENT OF COMMERCE. Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS. Richard W. Roberts, Director

Progress Report

on the

Performance of Bituminous Coated Cast-Iron Pressure

Pipe Buried in Various Soil Environments for Four Years

by

William F. Gerhold and Benjamin T. Sanderson

Reference :

(a) National Bureau of Standards Report No. 10,542, "Progress

Report on the Performance of Cast-iron Pressure Pipe Buried in Various

Soil Environments for Two Years", dated May 11, 1971.

Introduction :

Manufacturers and users are not in agreement regarding the actual

purpose of the bituminous coatings (shop coats) that are applied to

commercially available cast-iron pressure pipe in accordance with Federal and AWWA (American Water Works Association) specifications. Some

claim that the purpose of the coating is to protect the pipe during

handling and storage. Others claim that the purpose of the coating is

to protect the pipe from corrosion after installation in underground

environments. There is reason to believe that the latter is not true.

An investigation was initiated to determine the degree of protection of the cast-iron pressure pipe from corroison that may be derived by using these shop coatings when they are applied in accordance

with Federal Specification WW-P-421 and AWWA Specification CI 10-64.

For purposes of this investigation sufficient sets of coated and un- coated cast-iron pressure pipe specimens were buried at each of six

NBS soil corrosion test sites to allow for removal and evaluation at

specified time intervals. The intervals selected were 1, 2, 4 and

8 years with an additional set to be removed at a later unspecified

date. To date specimens have been removed from the various soils after

burial for 1, 2 and 4 years. Reference (a) contains the results

obtained from examination of cast-iron pressure pipe specimens after

exposure for one and two years. This report contains the results

obtained from examination of specimens exposed in the six soils for

approximately four years.

Materials :

Pipe materials were procured from commercial sources and were representative of that manufactured by two major producers of castiron pressure pipe. The material used in these tests were as follows:

(a) 2.5-in OD, nominal 2-in, Class 150, cast-iron pressure pipe

with a coal-tar-base bituminous coating.

(b) 2.5-in OD, nominal 2-in, Class 150, cast-iron pressure pipe

with an asphalt-base bituminous coating.
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(c) 2.5-in OD, nominal 2-in, Class 150, cast-iron pressure pipe

with no coating.

Specimen Preparation :

Five sets of specimens consisting of four specimens each of coaltar-base bituminous coated, asphalt-base bituminous coated and uncoated

cast iron pressure pipe were prepared for burial at each of the six

NBS scil corrosion test sites. Each specimen was approximately 12-in

long with a nominal wall thickness 0.25-in. In order to obtain the

loss in weight from corrosion due to exposure in the soil, the uncoated

specimens were weighed prior to burial. All specimens, coated and un- coated, were capped and sealed at each end to confine the corrosion to

the exterior surfaces.

Test Procedure : -

•

The specimens were buried in the six soil environments during 1967.

Four specimens of each system were buried approximately two to three

feet below the ground line.

Soils at the Test Sites :

The physical and chemical properties of the soils at the test

sites are given in Table 1. Descriptions of the soils at the test sites

are as follows

1. Site A. Sagemoor sandy loam is a well-drained alkaline soil

with a resistivity of 400 ohm-cm and a pH of 8.8 and is

typical of that found in vast areas of eastern Washington

and Oregon. The site is located on the Yakima Indian Reservation near Toppenish, Wash. The soil is consistent in com- position to a depth of at least 7 ft and supports abundant

growth of sage brush.

2. Site B. Hagerstown loam is a well-drained soil representative

of the majority of wel 1 -developed soils found in the eastern

part of the United States. The site is located at the Loch

Raven Reservoir of the Baltimore water department. The soil

consists of a brown loam about 1 ft deep, underlain by a reddish-brown clay that extends 5 ft or more to underlying

rock. The soil has a resistivity of 5,200 ohm-cm and a pH

of 5.8. Practically all the materials that have been investigated in the extensive NBS soil corrosion tests since 1922

have been exposed at this site, which, therefore, will serve

as a reference site in the correlation of data obtained for

specimens in the present program with data obtained from the

earlier tests.
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3. Site C. Clay soil is located in a large clay pit on level land

at Cape May, N. J. The soil consists of a plastic gray clay

to a depth of 6 in., underlain by gray clay mixed with patches

of brown clay to a depth of 12 in. This is underlain by a poorly drained very heavy plastic clay. The soil has a re- sistivity of 300 ohm-cm and a pH of 4.0.

4. Site D. Lakewood sand is a white, loose sand with some black

streaks occurring in places. The site is located in a welldrained rolling area at Wildwood, N. J., which is not subject

to overflow from the ocean except under unusual flood conditions.

The sand, which supports the growth of beach grasses abundantly,

has a pH of 7.3 and a resistivity of 30,000 ohm-cm.

5. Site E. Coastal sand is a typical white, coastal beach sand, with

a high content of black sand that occurs in streaks. This sand

is similar to Lakewood sand, except that at this site, which is

located on Two-Mile Beach at Wildwood, N. J., the sand is con- stantly saturated with salt water. The sand has a pH of 7.1

and a resistivity of 55 ohm-cm.

6. Site G. Tidal marsh is a soil typical of the poorly drained

marsh soils that are found along the Atlantic and Gulf coasts.

The site is located along a creek that empties into the Chesapeake Bay at Patuxent, Md. The soil is charged with hydrogen

sulfide and has a resistivity of 300 ohm-cm and a pH of 7.1.

Results :

One set of pipe specimens was removed from each of the test sites

after burial for four years. Visual examination of these specimens

before cleaning revealed localized corrosion attack on the exterior

surfaces on all of the specimens. The attack, in the form of pitting

corrosion, was similar to, although generally more severe, than that

noted on similar specimens buried for one and two years.

All specimens were hand scrubbed in hot-soapy water to remove soil

particles. The specimens were then rinsed in clear water and dried.

The coated specimens were immersed in varsol to remove the bituminous

coatings. All specimens were then further cleaned ul trasonically, to remove the corrosion products, by immersion in a hot 10% ammonium citrate

solution, rinsed in clear water and dried. If additional cleaning was required the specimens were wire brushed and the above cleaning procedure was repeated.

The uncoated specimens were then weighed to determine the weight

loss from corrosion by exposure in the soil environments. Pit depth

determinations were obtained for all specimens. These determinations

are summarized in Table 2. For purposes of comparison, similar determinations are also given for specimens buried for one and two years.
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The corrosion occurred as scattered localized pitting with some larger areas of general corrosion attack which appeared to initiate

at corrosion pits. Figures 1 through 6 show the specimens removed

from the six test sites after cleaning. The corrosion was shallow in

depth on all (coated and uncoated) specimens buried for approximately

four years at Sites D and E. The deepest penetration was observed on specimens exposed at Site C. One specimen at this site was perforated

by corrosion. In terms of depth of penetration the most severe corrosion

was noted on uncoated specimens exposed at Sites A, B, C and D and on coal-tar-base bituminous coated specimens exposed at Sites E and G.

However, the differences in depth of penetration by corrosion on uncoated and bituminous coated specimens exposed at Sites D or E are not

considered to be significant. Curves showing average depth of penetration for specimens exposed in the various soils are given in Figure 7.

Weight loss determinations for uncoated specimens show that the

soil at Site C was the most corrosive and the soils at Sites A and B were the least aggressive. Curves showing the average weight loss for

specimens exposed at the six NBS soil corrosion test sites are given

in Figure 8. ,

Conclusions :

-

Examination of uncoated and bituminous (coal-tar base and asphalt

base) coated cast iron pressure pipe specimens that had been buried

for four years at each of the six NBS soil corrosion test sites revealed corrosion attack on all of the specimens. The corrosion was of a scattered localized nature varying only in degree on the specimens ex- posed at the different test sites. The clay soil at Site C was the

most corrosive for the uncoated cast iron pipe specimens. There did

not appear to be any significant difference in depth of penetration by

corrosion on uncoated and bituminous (coal-tar base or asphalt base)

coated cast iron pipe specimens buried for four years in lakewood sand

(Site D) or coastal sand (Site E). The most severe corrosion in terms

of depth of penetration occurred on uncoated specimens exposed at Sites

A, B, C and D and on coal-tar-base bituminous coated specimens exposed

at Sites E and G. However, as noted above the differences in depth of

penetration by corrosion for coated or uncoated specimens exposed at

Site E were si ight.

While the coatings appear to provide some protection against cor- rosion in some of the soils after exposure for four years neither the

coal-tar base or the asphalt base bituminous coating appeared to perform well in all of the soils. This may be due partially to the re- latively short term of exposure in the environments. Studies on additional sets of uncoated and coated pipe specimens scheduled for removal

from the soils after longer periods of exposure should provide additional

information that may be considered more conclusive.
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TIME , YEARS

Figure 8. Average loss in weight (oz/ft^) for uncoated

cast iron pressure pipe buried up to approximately four

years in the various soils at the NBS Soil Corrosion

Test Sites.
NBS-l 14A (REV. 7-73)

U.S. ut^-l.<J^^_ulvlM. I.PbUl-ICAl ION OK Kb. FOR r NO. 2. Gov t Acce.";sion ^'^^'•^7;;,";^ ^^"^^ nbsir 74-435

3. Recipient's Acccs.sion No.

4. TITLE AND SUDTITLI:

Progress Report on the Performance of Bituminous Coated

Cast-iron Pressure Pipe Buried in Various Soil Environments for Four Years _

5. Publication Date January 1974

6. Performing Organization Code

7. AUTHOR(S) _ „ , ,„ . . r. 1 William F. Gerhold and Benjamin T. Sanderson

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work- Unit No. 3120449

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Tri Services

Department of the Navy

Naval Facilities Engineering Conmand

Washington, D.C. 20390

13. Type of Report & Period Covered

Progress Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant I bibliography or literature survey, mention it here.) ! An investigation was initiated to determine the degree of protection from corrosion | of cast-iron pressure pipe that may be derived using bituminous coatings. j Sufficient sets of coated and uncoated cast-iron pressure pipe specimens were ! buried at each of six NBS soil corrosion test sites to allow for removal and

evaluation at specified time intervals. The time intervals selected were

1, 2, 4, and 8 years with an additional set to be removed at a later unspecified

'

date.. To date specimens have been removed from the soils after exposure for

1, 2, and 4 years. This report summarizes the results obtained from these

tests.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Bituminous coatings; cast-iron pipe; corrosion, underground.

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USCOMM-DC 29042-P7