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Ku55%'vri27;1972 C,1 NBS-PUB-C 1959

NBS

PUBLICATIONS

NBS MONOGRAPH 127

NBS Papers

on

Underground Corrosion of Steel Piling

1962-1971
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NBS Papers

on

Underground Corrosion of Steel Piling

1962-1971

Corrosion of Steel Pilings in Soils,

Corrosion Evaluation of Steel Test Piles

Exposed to Permafrost Soils,

Performance of Steel Pilings in Soils,

Polarization Measurements as Related to

Corrosion of Underground Steel Piling

W. J. Schwerdtfeger and Melvin Romanoff

Metallurgy Division

Institute for Materials Research

National Bureau of Standards

U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secrefary

NATIONAL BUREAU OF STANDARDS, Lewis M. Branscomb, Director,

Issued March 1972

Washington, D.C. 20234
This monograph is dedicated to the memory of Melvin Romanoff,

who—until his death in October of 1970—was the guiding light

and motivating force for research at the National Bureau of

Standards on underground corrosion. His work is considered

by corrosion engineers throughout the world to be indispensable

for an understanding of the corrosion behavior of metals in

soils. The studies described in the monograph embody pioneering

concepts on the nature of driven piling corrosion developed by

Mr. Romanoff toward the end of his career. Therefore this

publication, which is a compilation of the papers resulting

from those concepts, serves as a fitting memorial for Melvin

Romanoff.

Library of Congress Catalog Number: 72-600037

National Bureau of Standards Monograph 127

Supersedes NBS Monograph 58

Nar. Bur. Stand. (U.S.), Monogr. 127, 63 pages (Mar. 1972) CODEN: NBSMA6

Issued March 1972

For sale by the Superintendent of Documents, U.S. Government Printing Office Washintgon, D.C. 20402 (Order by SD Catalog No. C 13.44:127). Price 65 cents.
Contents

Page

Corrosion of Steel Pilings in Soils, M. Romanoff 1-1

Corrosion Evaluation of Steel Test Piles Exposed to

Permafrost Soils, M. Romanoff 23-6

Performance of Steel Pilings in Soils, M. Romanoff 31-14

Polarization Measurements as Related to Corrosion of

Underground Steel Piling, W.J. Schwerdtfeger 40-107

III
ABSTRACT

This monograph is a collection of published papers on underground

corrosion of steel piling. The papers are as follows:

(1) Romanoff, Melvin, Corrosion of Steel Pilings in Soils, Nat. Bur.

Stand. (U.S.), Monogr. 58, (Oct. 1962).

(2) Romanoff, Melvin, Corrosion Evaluation of Steel Test Piles Exposed

to Permafrost Soils, Proceedings 25th Conference, National

Association of Corrosion Engineers, page 6 (March 1969).

(3) Romanoff, Melvin, Performance of Steel Pilings in Soils, Proceedings

25th Conference, National Association of Corrosion Engineers, page

14 (March 1969).

(4) Schwerdtfeger , W. J. , Polarization Measurements as Related To Corrosion of Underground Steel Piling, J. Res. Nat. Bur. Stand. (U.S.),

75C (Eng. and Instr.) No. 2, 107-121 (April-June 1971).

The papers describe corrosion of various types of steel piling

exposed underground in the United States under climatic conditions

ranging from semi-tropical to frigid. Corrosion is described on driven

piling above and below the water table after many years of exposure in

soils having resistivities between 78 and 50,000 ohm-cm and ranging in

pH from 2.3 to 8.8.

One of the papers demonstrates the value of a polarization

technique in measuring corrosion. Polarization data were obtained on weighed steel pipe specimens exposed underground for seven years in

backfilled soil trenches in the vicinity of driven sheet piling. The

technique was evaluated by comparing calculated cumulative weight losses

of specimens with their actual weight losses. The technique was also

shown to be applicable to underground pipe piling.

Kew words: Active region; aerated soil; corrosion; disturbed soil;

excavated; extracted; H-piling; instantaneous corrosion rate; mill

scale; permafrost region; pipe piling; pit depth; polarization; sheet

piling; undisturbed soil; weight loss.

rv
Selected NBS Papers on Underground Corrosion of Steel Piling

Preface

The papers included in this monograph have been previously published. The work was under the direction of the National Bureau of Standards with excellent cooperation from the American Iron and Steel Institute and Corps of Engineers, Lower Mississippi Valley Division,

Office of the Chief of Engineers. For those concerned about the

vulnerability of steel piling to corrosive soils and fills, this com- posite publication should be of interest.

The papers reveal the difference in the nature and extent of cor- rosion observed on driven underground piling and that found on steel ex- posed to soil in backfilled trenches. A distinction is made between so- called undisturbed and disturbed soil. Strictly speaking, in reference

to corrosion, there is no undisturbed soil. The difference between the

two soil conditions must be considered as being relative. By way of

definition, herein, an undisturbed soil is described as an underground

environment disturbed only by penetration from the driven piling coupled

with the assumption that there was no prior disturbance by recent

excavation.

A brief statement in reference to each of the four papers follows.

The first paper, "Corrosion of Steel Pilings in Soils" (Monograph 58)

describes the physical appearance of piling after exposure from 7 to 40

years. Piles were extracted at eight locations and soil excavated from

sheet piling at eleven sites for inspection and pit depth measurements.

The piles were located in Southern States east of the Mississippi River.

Soil resistivities varied from 300 to 50,000 ohm-cm and pH from 2.3 to

8.6.

The second paper, "Corrosion Evaluation of Steel Test Piles Exposed

to Permafrost Soils", pertains to observations and pit depth measurements on piling in Fairbanks, Alaska. Piling had been exposed to soil

affected by both permafrost and thawing conditions. Inspections were

made on nine steel H and pipe piles after extraction which followed 6

to 11 years of exposure in soils ranging in resistivity from 1350 to

11,500 ohm-cm and in pH from 5.4 to 7.6.

The third paper, "Performance of Steel Pilings in Soils", involves

physical inspection of steel piling in 25 locations covering much of the

United States. Eight of the piles (all sheet piles, except one) were

extracted for evaluation of corrosion and measurement of pit depths.

The piling had been exposed from 21 to 50 years in soils having resistivities ranging from 78 to 41,000 ohm-cm and pH from 4.7 to 8. Thirteen

of the piles were of the sheet type, inspected by excavation of adjacent

soil, the age of piling being from 14 to 30 years. The four remaining

piles, also sheet type, had been coated with coal tar enamel and exposed

V
8 to 24 years. Wherever excavations were made for the purpose of piling

inspection, sections of piling were cut from the most severely corroded

areas and shipped to the laboratory for removal of corrosion products

and for pit depth measurements.

The final paper of this monograph, "Polarization Measurements as Related to Corrosion of Underground Steel Piling", relates how corrosion

observed on piling at 4 sites, described in the first paper (Monograph

58) , compared with that on weighed steel pipe specimens exposed nearby

in backfilled trenches. In addition to weight losses and pit depths,

involving exposure periods of 1,2,4 and 7 years, polarization measurements were made at periodic intervals on one of four specimens designated

for each exposure period at each of the 4 sites. Based on verification

by actual weight losses, following removal of corrosion products, it was demonstrated how periodic measurements of instantaneous corrosion

currents could be used to calculate cumulative metal losses in reasonable agreement with actual weight losses. Finally, the corrosion rate

measurement technique, based on specific changes in the slopes of

polarization curves, was applied to measuring the instantaneous cor- rosion taking place on 12 in. diam. (30.5 cm) pipe piles, one 19 ft.

(5.8 m) and the other 72 ft. (22 m) in length, exposed to a corrosive

underground environment for 12 years.

The National Bureau of Standards continues to study the corrosion

of underground steel piling. In 1966, three piling sites were installed

at Montreal, Quebec, Canada during construction of the Trans-canadian

highway. It is an international cooperative project. At each site,

several steel H-piles, 12 in x 12 in x 30 ft (30.5 cm x 30.5 cm x 9.2 m)

,

were driven to bedrock and the upper ends of the piles exposed to ex- cavated soil and fill. At one site, all piles are exposed bare. At the

second site, the upper part (about 5 ft or 1.5 m) of the piling, exposed

to the fill soil, was protected with a coal-tar epoxy coating. At the

third site, molded concrete caps were substituted for the epoxy coating.

At each site, one pile identical with the others is placed horizontally

in a backfilled trench.

At Montreal, polarization measurements have been made on a yearly

basis since installation of the piling. A paper is currently under

preparation describing the physical appearance of piling removed from

each site after three years of exposure and also comparing physical

measurements with corrosion rates as calculated from polarization data.

Measurement of instantaneous corrosion rates will continue to be carried

out yearly and removals of piling be done at prescribed intervals. Following removals, the results will be published.

The projects included in this Monograph have been sponsored by the

American Iron and Steel Institute, New York, N. Y., and their financial

support is gratefully appreciated.

W. J. Schvrerdtfeger

VI
UNITED STATES DEPARTMENT OF COMMERCE • Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin. Director

Corrosion of

Steel Pilings in Soils

Melvin Romanoff

Reprinted from the Journal of Research of the National Bureau of Standards—C. Engineering and Instrumentation

Vol. 66C, No. 3, July-September 1962

National Bureau of Standards Monograph 58

Issued October 24, 1962
Contents

Page

1. Introduction 1 2. Literature survey 1 3. Inspection procedure 3

3.1. Piles extracted from location 3

3.2. Piles inspected in excavated test holes 3

3.3. Soil characteristics and properties 3

3.4. Thickness measurements 4

4. Results of inspections 4

4.1. Extracted piles 5

a. Bonnet Carre Spillway, New Orleans, Louisiana 5

• „_b. H -piles at Sparrows Point, Maryland 5

c. Corps of Engineers, Dam and Lock No. 8, Ouachita River,

Arkansas 6

d. Grenada Dam Spillway, Grenada, Mississippi 7

e. Sardis Dam Outlet, Sardis, Mississippi 8

f. Chef Menteur Pass, New Orleans, Louisiana 9

g. Wilmington Marine Terminal, Christiana River, Delaware. 9

h. Lumber River, near Boardman, North Carolina 10

4.2. Pilings exposed in excavations 11

a. Memphis Floodwall, Memphis, Tennessee 11

b. Vicksburg Floodwall, Vicksburg, Mississippi 12

c. Sardis Dam Spillway, Sardis, Mississippi 13

d. Grenada Dam Spillway, Grenada, Mississippi 14

e. Berwick Lock, Berwick, Louisiana 15

f. Algiers Lock, New Orleans, Louisiana 16

g. Enid Dam Spillway, Enid, Mississippi 16

5. Discussion 17

6. Summary 21

7. References 22
Corrosion of Steel Pilings in Soils ^

Melvin Romanoff

(April 18, 1962)

Steel pilings have been used for many years as structural members of dams, floodwalls, bulkheads, and as load-bearing foundations. While its use is presumably satisfactory, no

evaluation of the material after long service has been made. In cooperation with the American Iron and Steel Institute and the U.S. Corps of Engineers, the National Bureau of Standards has undertaken a project to investigate the extent of corrosion on steel piles after many

years of service. Results of inspections made on steel pilings which have been in service in various under- ground structures under a wide variety of soil conditions for periods of exposure up to 40

years are presented. In general, no appreciable corrosion of steel piling was found in undisturbed soil below

the water table regardless of the soil types or soil properties encountered. Above the water

table and in fill soils corrosion was found to be variable but not serious.

It is indicated that corrosion data previously published by the National Bureau of Standards on specimens exposed under disturbed soil conditions do not apply to pilings

which are driven in undisturbed soils.

1. Introduction

Steel pilings have been used underground for many

years to transmit loads to lower levels or to resist lateral pressures due to earth and water. Pipeand H -piles are used as load-bearing foundations for the first purpose; sheet piles are used as structural

members of dams, floodwalls, bulkheads, and other

installations for the latter purpose. While its use

is presumably satisfactory because no structural

failures have been attributed to the corrosion of underground piles, there is considerable concern

that damaging corrosion might occur on steel piles

driven in different soil environments. This concern

is enhanced by the corrosion that occurs in disturbed

soils on actual structures, and by the results of

corrosion investigations of the type conducted by

the National Bureau of Standards [Ij,- in which

corrosion of iron, steel, and other metals in different

soil environments has been observed to range from

a negligible rate to a very high rate. As a basis for more accurate estimates of the useful

life of steel pilings in soils, the National Bureau of Standards, in cooperation with the American Iron

and Steel Institute and the U.S. Corps of Engineers,

has undertaken a project to investigate the extent of

corrosion on steel piles after many years of service.

Excavations to depths of 15 ft were made adjacent

to various floodwall and dam structm'es along the

Mississippi River to expose sheet steel pUings which

have been in service from 7 to 20 yr. Soil samples

and sections of the piles were returned to the laboratory for further study. The extraction of steel sheet and H -piles from other locations permitted

examination of the entire length of piles at greater

depths and for exposure periods up to 40 yr.

A paper presented at the Soil Mechanics and Foundations Division, American

Society of Civil Engineers Convention at Houston, Texas, February 22. 19G2.

2 Figures in brackets indicate the literature references at the end of this paper.

In this paper are presented the results obtained to date from the inspections of steel pilings. The in- vestigation wiU be continued by additional inspections of pilings in other parts of the country in order to cover a wider range of soil environments.

2. Literature Survey

Although many references pertaining to the

behavior of steel piling have been made in the

literature dm-ing the past years, no systematic

evaluation of the material after long service in soils has been made. Many of the reports make general

statements without giving much or any information

regarding the history of the structmre or actual

measurements relating to the condition of the piles

examined.

Statements regarding the undergroimd corrosion

of steel piles are made in two texts on substructure

design. Andersen [2] indicates that corrosion is not

a serious problem when steel piles are completely

below ground-water level but it must be guarded

against where sea water is present, where ground

water has a high salinity, or where the piles are subject to alternate wetting and drying. Hool and

Kinne [3] state that the amount of corrosion on steel pipe piles in the ground is negligible. Piles that

have been in the ground for over 25 at have shown

upon removal that corrosion did not penetrate more

than %4: in. into the metal. They also report that

corrosion is slight on sheet pile below ground-water

level. Mason and Ogle [4] inspected a large number of

steel pile foundations in bridge structures in Nebraska. They found little, if any, corrosion at depths

greater than 18 in. below the stream bed or ground

water level. It was estunated that the decrease in section due to corrosion had not been more than 1 percent in 20 yr, except in an area where the soils are saline to a marked degree. In that locality

1-1
several steel foundations showed a loss of section of

about 2 to 2.5 percent.

The Harbor Commissioners of Quebec City [5] concluded from examination of a 16-yr-old steel sheet pUe in the St. Charles River that steel buried

in sand or ground or submerged in water, is less exposed to damage by corrosion than when exposed

to the air. The examination in soil was limited to one sample of the pUe which was 2 ft below ground

surface. The sample was covered with a heavy

crust of rust and difBcult-to-remove corrosion products. After cleaning by sand blasting a good state

of preservation was evident.

The Los Angeles Department of Engineering [6] removed some 39-yr-old piers which consisted of concrete cast in 4-ft diam cylindrical shells made of

steel plates. Forty-one feet of the cylinders were below grovmd, the lower 11 ft below the groundwater level and the upper 30 ft in dry sand and

gravel, part of which was wet occasionally. Some

pits having a maximum depth of Ke in. were observed on the shell below ground water. Slightly more

{)itting was found in the zone above ground-water

evel; the average depth of the pits was again about

Ke in. It was found on examination of steel sheet piling

which was removed after exposm-e for 19 yr from

a bridge over the Monongahela River at Pittsburgh

[7] that the zone between the water line to 2 ft below showed a 15-percent reduction in weight.

The zone extending from 2 ft below the water line to and below the mud line was practically unaffected

by corrosion. It was pointed out that dm"ing most

of the year the river contained some free sulfuric

acid.

In a report concerned with a study of the expected

life of steel H -piling and thin wall cylinder piling

under highway structiures in the Texas Gulf Coast

area, Gallaway [8] concluded that, with the exclusion

of muck and peaty soils, steel piling driven in ordinary soil to a point below the water table should

suffer very little corrosion except in the zone ex- tending not more than 2 or 3 ft below the soil-water

interface. Gallaway does not provide actual data

to support the conclusion, nor does he indicate the

extent of corrosion encountered in soils of muck and

peaty materials.

Greulich [9] described the condition of a 12-in. 72-lb H-pUe after exposure for 12 yr to a depth of

Table 1. Thickness (percent of original) of

72 ft through various layers of sand and clay in the

Texas Harbor at Houston. Calculations based on

examination of a section of the pile between 1 and 2

ft below the mud line indicate that it would take a minimum of 85 yr for corrosion to reduce the thick- ness of the pile to the extent that it would not

permit a safe design load of 17,000 psi (65-ton

service load) when acting as a fully supported

column. Greulich also reported on the excellent

condition of a 122-ft length of H-pile which was

extracted 17 yr after installation at Bonnet Carre

Spillway in Louisiana. A discussion of the condition

of this pUe from data made available by the Lower

Mississippi Valley Division of the Corps of Engineers

wUl be given in a following section of this paper.

Steel piles which extended from 3 ft below the

mud line into the atmosphere above the tidal range were exposed at six naval harbors for periods ranging

from 13 to 27 yr [10]. At each of the sites the piles

corroded at a higher rate in a zone located above the

mud line than at the mud line level and below. The

greatest corrosion generally occmred in the area

of the splash zone above the high-water mark.

The averages of the original pile thicknesses and

the extent of maximum corrosion on the piles at and below the mud line are shown in table 1. The

corrosion rates at the 1- and 3-ft levels (below the

mud lines) varied only slightly from those which

occurred at the mud line, except at San Diego where

a high corrosion rate was found 3 ft below the mud

line. This was attributed to local conditions which

produced a lower pH in this level or to oxygenconcentration cells. Lipp [11] observed from a survey of sheet steel pUe bulkheads at Miami Beach that the steel below

the sand line was in practically the same condition

as the day it was installed, 8 yr previously. A 14

percent loss in piling thickness was observed in the

areas exposed above the sand line. The Beach Erosion Board of the Corps of Engineers

[12, 13] conducted extensive investigations on the

deterioration of sheet pilings in such shore structiires as jetties, groins, harbor, and beach bulkheads. In

a report [12] pertaining to the behavior of ^^-in. steel pile groins at Palm Beach, Fla., it was shown

that the average rates of loss in steel thickness of the

parts not exposed to sand abrasion are relatively

moderate, being about 0.011 in./yr for atmospheric

piling after exposure at naval harbors [10]

Level

Harbor location

Boston Puget Sound San Diego Norfolk Pearl Harbor » Coco Solo »

Avg b Min " Avg Min Avg Min Avg Min Avg Min Avg Min

ft Mud line 0. -3

78.

92.8

81.6

63.7

84.8

78.2

96.4

95.3

95.1

88.6

89.6

88.0

94.3

92.5 64.6

90.4

89.4

56.2

91.0

94.0

93.6

82.4

84.6 88.4

93.2 96.8

96.0

86.6

88.0 82.0

88.5

93.8

94.4

72.2 '81.6

80.6

Years in service 17 13 17 27 13 24

" Piling coated with bituminous material.

i> Avg—average based on weight loss.

« Min—minimum based on thickness measurements on the thinnest section of test sample. This represents the maximum corrosion in the specified 2-2
exposure, 0.005 in./yr for wetting and drying ex- posure, and 0.001 in./yr for subsand exposure. It was estimated that the time required for the perforation of /8-in. steel would be, respectively, 34 yr, 75

yr, and 375 yr. In the abrasion zone, the steel lost an average thickness of 0.117 in./yr.

Ra3mer and Ross [13] issued a comprehensive re- port on the durability of sheet steel pilings in 94

structures which have been in service for various

periods up to about 25 yr along the Atlantic Coast

and the Gulf Coast of Florida. Comparison of rates

of loss of thickness for steel piles used in the bulkheads

indicates that lack of backfill for all or part of the

time greatly increased the rate of loss. For beach

bulkheads the rate of loss rapidly decreased as the

sand cover increased. For groins and jetties the

rates of loss were uniformly high except for those

covered on both sides. It was concluded that sand

or earth cover materially decreased the loss of thick- ness of steel piles used in shore structures, the rates

of loss for all practical purposes being negligible for pilings covered on both sides. Four groups of piles were pulled from moderately polluted sea water lo- cations during the period of investigation, three of

the groups located at Miami, Fla., which have been

in service for 10 yr, and one group which had been

in service for 18 yr at Stamford, Conn. Approximately 10 ft of the piles were driven below the ground

line. The average annual rates of loss of thickness

of the piles varied between 0.0009 and 0.0022 in. at the four sites. The maximum rate, which generally

occurred within the zone 2 to 3 ft below the ground

line, was 0.003 in./yr.

Bjerrum [14] made measurements on steel piles

which were pulled from three locations in Norway.

Observations on a 17-ft length of pile which was

driven 17 yr prior to inspection in a silty clay having

a resistivity between 2,000 and 4,000 ohm-cm showed

an attack less than 0.003 in. Another 17-ft pile was

pulled after exposure for 18 yr in a clay soil of marine

origin. In spite of the low resistivity of this soil, 50 ohm-cm, the corrosion varied from 0.01 to 0.02 in. The third pile, exposed to a low resistivity marine

clay for 6.5 yr, showed maximum corrosion of 0.10

in. which corresponds to an average rate of more

than 0.01 in./yr in a 6-ft zone located between 11 and 17 ft below the ground line. Corrosion above or below this zone on the remaining pile areas did not

exceed 0.02 in., or a rate of 0.003 in./yr. No mention

is made of the water line elevation at any of the

locations where the Norwegian piles were pulled.

The writer, in view of his experiences in the examination of steel piles, suggests the possibility that the

accelerated attack, reported by Bjerrum on the third

pile, may have occurred in a water table zone.

3. Inspection Procedure

3.1. Piles Extracted From Location

Steel H -piles were pulled from two locations and

steel sheet piles were pulled from six locations. The

writer participated in all inspections on the pilings

with the exception of the H-pile extracted from the

Bonnet Carre Spillway. The data pertaining to the

latter inspection were obtained from the files of the

Corps of Engineers, U.S. Army Division, Lower

Mississippi Valley.

After the soil and corrosion products were cleaned

from the pile surface by utilizing wire brushes and

scrapers, the extent of corrosion was determined by

visual observation, pit depth measurements made

with micrometers, and thickness measurements made

with calipers.

Pile sections pulled from the Ouachita River Dam

and Lock No. 8, the Grenada Dam Spillway, the Sardis

Dam Spillway, and the Lumber River Cofferdam

structure were shipped to the National Bureau of

Standards. These were cleaned by sandblasting to permit a more comprehensive examination of the

pile surfaces in the laboratory.

The results of aU the inspections of the extracted

piles are given in section 4.1.

3.2. Piles Inspected in Excavated Test Holes

At locations where it was not possible to pull the

piles without disturbance to the existing structure,

test holes were excavated adjacent to the sheet steel pilings to expose a width of piling at each location.

At the start of the investigation it was planned to expose the pilings to a maximum depth of 15 ft from the surface, but at most locations the water

table did not permit excavating to this depth.

Two excavations were made at each of four Corps

of Engineers structures and one excavation at each

of three Corps of Engineers structures to examine

sheet steel pilings which have been in service in a variety of soil environments.

The soil and corrosion products were removed

from the exposed piling by wire brushing and

scraping. The condition from the top of the piles to the depth of excavation was determined by visual

observation and pit depths were measured.

A portion of the pile web, approximately 1 ft by

2 ft, was cut from the area that showed the maximimi

amount of corrosion at each location. The removed

portions were shipped to the Vicksburg District

Foundation and Materials Branch Laboratory of

the Corps of Engineers, and then to the National

Bureau of Standards for further examination.

The results, of examinations made on the piles in the excavated test holes are given in section 4.2.

3.3. Soil Characteristics and Properties

Determinations of the soil types for the different

horizons at the locations where piles were pulled were made from soil samples adhering to the walls

of the pilings. To serve as an additional check on the

soil types, engineers in charge of the structures provided soil boring data for the excavations at Bonnet

Carre Spillway, Grenada Dam Spillway, Wihnington

Marine Terminal, and Sparrows Point. Soil samples removed from the pUe surfaces were shipped to the National Bureau of Standards laboratory for measurements of soil resistivity and ^H; at some

locations, where shown in section 4, soil resistivity
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determinations were made at the site with Shepard

Canes or by the 4-pin method.

Determinations of the soil type at the sites where

test holes were excavated adjacent to the pilings were made by visual inspection from the surface to the floor of the pit. Soil resistivities were measured

at different levels by inserting Shepard Canes in the

walls and floor of the excavation. Additional soil resistivity measurements were made at each site by

the 4-pin method at 10-ft, 20-ft, and 30-ft pin

spacings to give the average resistivities of the

volume of soil from the surface to the depths corre- sponding to the respective spacings. The latter were made at the time of the pile inspection and at approximately 15 day intervals thereafter for a

period of 7 months. The 4-pin resistivity measure- ments tabulated in section 4 represent an average of

the many determinations.

During excavation of the test holes, samples of

undisturbed sod, each sample having a volume of not

less than % ft,^ were taken at different depths

chemical and physical properties of the samples were determined at the Waterways Experiment Station Laboratory. Additional samples of the same soils collected in tightly sealed pint jars were shipped to the National Bureau of Standards for laboratory

measurements of pH and resistivity, the latter cor- rected to 70 °F. Data pertaining to the soil t3rpe,

resistivity, and pH are given with the inspection

results for each location in a following section.

Other physical and chemical properties of the soils at the elevation from which portions of the pilings were removed are listed in table 2.

3.4. Thickness Measurements

The average thickness measurements reported for the extracted piles represent an average of many

measurements made by means of calipers in the pile zone indicated, and takes into account corrosion on

the two sides of the pile surface. Average thickness measurements on the piles in- spected in the test holes were confined to the 1 ft by 2 ft pile samples which were removed and shipped

to the laboratory. After cleaning by sandblasting,

the three most corroded 1-in.- areas were selected on

each sample showing significant corrosion. Each

area was divided into 25 sections on both sides of the

pile sample and the pit depths in each section were

determined. The sum of the average of the 25 pit

depths on the two surfaces of each area was used to

calculate the average reduction in pile thickness at the base of the pits.^ These values actually repre- sent the average reduction in pile thickness of the

most corroded areas, 1 in.^ in size, on the piles.

4. Results of Inspections

Historical facts pertaining to the steel pilings of

various structures, the characteristics of the soils, and the condition of the piles are presented herewith

for the piles inspected after extraction from the soil, and for those inspected in the test holes, respectively.

3 Hereafter the reduction in thickness refers to this limitation. 4-4
4. 1 . Extracted Piles

a. Bonnet Carre Spillway, New Orleans, Louisiana

History:

A 12-in., 65-lb, test H-pile was driven to a deptli

of about 122 ft below natural ground surface in a swamp near the river side toe of the west approach

ramp to the Airline Highway Bridge across Bonnet

Carre Spillway.

Date pile driven: 1933

Date pile fulled: 1950

Age oj piling: 17 years

Piling exposed: Elevation +2.0 to —120 ft msl.* Ground line at +2.5 ft; water line at 0 ft. Soil characteristics: +2.5 to —7 ft: Soft dark gray organic sUty clay. —7 to —40: Very soft dark gray highly organic

clay and silt layers with few thin layers of peat and

few thin layers of fine gray sand.

—40 to —62: Very soft dark gray clay and silt layers, slightly organic. —62 to —67: Dense yellowish brown silty sand

with hard clay layers at bottom.

—67 to —120: Light bluish gray plastic clay,

hard at top, very stiff at bottom.

Soil resistivity and pH

Elevation

+ 2.5 to -7.5.

+ 2.5 to -17.5—.

+ 2.5 to -27.5.__.

+2.5 -1.5

-22.

-45-

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Ohm-cm

920 (4-pin).

1,050 (4-pin).

960 (4-pin).

540 (4-pin).

840 (4-pin). 770 (4-pin).

460 (4-pin).

800 (4-pin).

680 (4-pin).

700 (Shepard Canes)

750 (Shepard Canes).

400 (Laboratory) 400 (Laboratory)

6. 7

7. 8

8. 1

Condition of pile:

The space between the flanges of the pile was

completely filled with soil and a layer of soil adhered

to the outer edges of the flanges. Examination

after cleaning showed no measurable corrosion.

Mill scale was intact over almost the entire surface

except for the 3-ft section in the area of the water

table between elevation +1.5 and —1.5 ft. In this zone a crust of light colored hard substance coated

the metal. Slight metal attack was found under

the crust.

<msl refers to mean sea level. All elevation values in the paper refer to msl,

nless otherwise noted.

b. H -Piles at Sparrows Point, Maryland

History: In 1942, several 14-in. H-piles liaving an average

flange thickness of 0.55 in. were driven at the Spar- rows Point Plant of the Bethlehem Steel Company

for test purposes. The American Iron and Steel Institute arranged with the Bethlehem Steel Company

to extract two of the piles and to permit the writer

to inspect and report on the condition of tlie piles as part of this investigation. The piles were 139 ft in length, 136 ft of which was driven below the ground

line. The two piles were separated by a distance

of 100 ft. Date piles driven: 1942

Date piles pulled: November 1960

Age of piling: 18 years

Piling exposed: Elevation +13 to —126 ft. Ground

line at +10 ft. Soil characteristics: This area was originally a peninsula surrounded by

shallow water and marsh which was filled to about

elevation +10 ft with slag and cinders.

+ 10 to 0 ft: Slag and cinder fill with some fine sand. Water line at +7.0 ft for pile No. I-S, and

at +6.4 ft for pile No. II-S.

0 to —10: Natural soil starts at 0 ft. Light gray

silty clay containing appreciable sand, underlain by

a stiff brown silty clay and marbled gray clay. — 10 to —25: Light brown sandy silt to a soft dark gray silty clay at —15 ft. —25 to —90: Transition from brownish to dark

gray silty clay mixed with peat and organic matter

at some levels. —90 to —95: Dark brown silt underlain by fine brown sand.

—95 to —110: Transition from sand of different textures to dark brown silt. — 110 to —120: Coarse brown sand and gravel

and some fine gray sand. — 120 to —126: Brownish and gray stiflp clay.

Soil resistivity and pH

Pile No. Elevation Resistivity pH

fl Ohm-cm

I-S -4 2, 500 3. 7 -24 5, 100 4. 8 *-24 1, 410 5. 6 *-51 1, 820 7. 3 -54 3, 000 5. 4 *-54 1, 500 6. 1 *-83 1, 700 6. 3 -83 1, 370 6. 3 *-92 2, 100 6. 4 -102 7, 200

-120 12, 400 6. 4

II-S -1 1, 130 6. 6 -4 4, 000 4. 7 -24 2, 500 4. 9 -51 1, 450 6. 8 -92 2, 500 6. 1

Laboratory measurements made on soil samples taken from extracted pile. All other measurements made on soil sample borings obtained 1 ft from pile.

5-5
Condition oJ piles:

The pattern and amount of corrosion on the two

piles were about the same. Corrosion was confined

to two areas. One area extended from the top of the

piles, which was above ground level, and extended

through the zone exposed to the cinder and slag fill in the water table zone. The other corroded area occurred between elevations —115 to —118 ft where

the piles passed through a sand and gravel bed.

Pile II-S was cleaned by sandblasting prior to examination, and pile I-S was cleaned with scrapers and wire brushes. Except as noted otherwise, the

corrosion measurements I'eported are the maximum

observed on the two piles.

+ 13 to +8 ft: Slight uniform corrosion and iso- lated pitting. Maximum depth of pitting, 35 mUs.

At least 50 percent of the mill scale was intact.

Maximum reduction in flange thickness, 3 percent.

+8 to +6: This is the zone showing the maximum

corrosion on both pUes. The water line was at +7 ft for pile I-S, and at +6.4 ft for pile II-S. The mill scale was practically entirely removed; uniform cor- rosion and many pits were present. Most of the

pitting occurred within the 1-f t area above and below

the water line. The two maximum pit depths measured on pile I-S were 112 and 90 mils, a few pits were found between 60 and 75 mils, and other pits less then 60 mUs in depth. On pile II-S, there were 10

pits between 55 and 72 mils in depth and other pits

less than 50 mils in depth. The flange surfaces were more severely attacked than the web surfaces. Measurements made on the flange within 1-ft of

the water line showed that the original cross section

of pile I-S was reduced by an average of 29 percent.

For pile II-S, the average reduction was 14 percent.

FiGUEE 1. Sections of the 139-ft H-piles pulled from Sparrows Point, Maryland, after exposure for 18 years.

Left, water table zone consistiDg of fill material; center, clay soil stratum at about elevation —30 ft; and right, coarse sand and gravel stratum underlain by clay between elevations —110 and —126 ft. The pile was cleaned by sandblasting. Note the excellent condition of the butt weld at the splice in the center photograph.

The reduction m pile thickness due to corrosion ] tapered off rapidly as the distance away from the

j water line was increased. The average reduction

j in flange cross section on the zone between 1 ft and

2 ft below and above the water line was 2 to 3

percent. No perceptible reduction in flange thick- ness was noted 4 ft above or below the water line. : +6 to —4: Mill scale intact over 90 percent of the : pile surfaces. Negligible metal attack and local- ! ized pits which were less than 20 mils in depth, { except for a few pits between 20 and 31 mils. ! —4 to —11: Slight metal attack in a 4-in.^ area ! with a maximum pit depth of 18 mils on pile II-S ' only. Mill scale intact over 95 percent of surface. j — 11 to —115: No measurable pit depths. Mill | scale intact over 95 percent of surface. i — 115 to —118: At this depth the piles passed I through a sand and gravel stratum. The steel surfaces were uniformly corroded and contained ! many localized pits which generally ranged in depth j up to 50 mils; 12 pits measured between 50 and 65 ! mils and 2 pits had depths of 80 and 95 mils. The 1 average reduction in flange thickness measured 9 ! and 4 percent, respectively, for pile I-S and for i pfle II-S. — 118 to —126: Practically unaffected by corrosion. Mill scale more than 95 percent intact.

Figure 1 shows the condition of pile II-S at three ; different levels. j

j

c. Corps of Engineers, Dam and Lock No. 8, Ouachita River,

j Arkansas j History: \ An end pile was pulled from the upstream abut- i ment wall of the Corps of Engineers, Dam and Lock ' No. 8 on the Ouachita Kiver near El Dorado, Ark.

6-6
The pile was a shallow-arch sheet pile having a 15-in. driving width, and a web thickness which varied

from 0.45 in. at the center to 0.67 in. near the edges.

The length of the pile was 15 ft, the top 2 ft of which was embedded in a concrete cap. Date pile driven: 1921

Date pile pulled: June 1961

Age oj piling: 40 years

Piling exposed: Elevation 67.5 to 52.5 ft. Ground

line at elevation 78.5 ft; water line at 76.5 ft. The

top of the pile was encased in concrete to elevation

65.5 ft. Soil characteristics: 78.5 to 76.5 ft: Silty clay fill with some organic

material.

76.5 to 64.5: Blue clay containing about 40 per- cent sand.

64.5 to 60.5: Stiff blue clay containing about 10

percent sand.

60.5 to 52.5: Very stiff blue clay containing about

2 to 3 percent sand.

Soil resistivity and pH

Elevation

ft 78.5 (Surface) . -

65.5.

60.0

55.0

Resistivity

Ohm-cm

2,900 (Sliepard Canes)

3,200 (Laboratory)

1,540 (Laboratory)

1,540 (Laboratory)

pH

4 3

6. 2

4. 6

Condition oj pile

The entire length of the pile was driven below the

water table. Corrosion was confined to a 2-ft sec- tion on the river side of the pile between elevation

59.8 to 61.8 ft. Pitting occurred in 11 places,

each about 1 in.^ in area, along the fingers of the pile.

The maximum pit depth was 26 mils and others

ranged up to 22 mils. Several pits having a maximum depth of 20 mils were found in a 3-in^. area in

the center of the web. Ninety percent of the mill

scale was intact in this moderately corroded zone. At least 95 percent of the original mill scale was

found to be intact on the remaining areas of the pile,

and no measm-able pits or corrosion beyond the mill

scale was observed. Based on the maximum pit

depth, the total loss of pile thickness in the cor- roded zone could not exceed 5 percent of the original

pile thickness.

The portion of the pile which contains the measurable pits is shown in figure 2.

d. Grenada Dam Spillway, Grenada, Mississippi

History:

A type A sheet pile was pulled for examination

from the end of the north upstream wingwaU of the

Grenada Dam Spillway at Grenada, Miss. The pile was 14 ft in length, had a driving width of 19^ in. and a thickness of % in. Date pile driven: October 1948

Date pile pulled: July 1960

Figure 2. Sandblasled 3-ft section from the 40-year-old piling extracted from an abutment wall in the Corps of Engineers Dam and Lock No. 8 on

the Ouachita River near El Dorado,

Arkansas.

The section was exposed about 18 ft below

the ground line and it is the only portion of the

pile which contained pits of measureable depth. The maximum pit was 26 mils in depth. Age of piling: 12 years

Piling exposed: Elevation 251.5 ft to 237.5 ft; ground

elevation at 256 ft, water table much below the

bottom of pile.

Soil characteristics: 256.0 to 250.5 ft: Fill soil, reddish brown sandy

loam.

Soil resistivity and pH

Elevation

fl 256 to 246

256 to 236

256 to 226

256

250

245.5 241

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Ohm-cm

11,700 (4-pin).

15,400 (4-pin).

13,900 (4-pin).

4,600 (4-pin)

9,600 (4-pin).

6,900 (4-pin).

4,300 (4-pin).

7,300 (4-pin).

6,200 (4-pin)

2,800 (Shepard Canes).

> 4,000 (Laboratory)

>4,000 (Laboratory)

3,800 (Laboratory)

pH

4. 9

4. 9

3. 6

657852—62 2 7-7
Figure 3. Sections {1.5 fl by 1 ft) cut from a piling which was pulled from the north upstream

wingwall of the Grenada Dam Spillway at Grenada, Mississippi, after exposure for 12 years.

Sections were cleaned by sandblasting. D103A, section of pile exposed to fill soil. D103B, section of pile exposed to natural soil.

250.5 to 246.6: Fill soil, tan silty sand.

246.5 to 244.5: Natural soil layer, grayish blue

fractured shale. 244.5 to 237.5: Transition from light brown to gray clay. Gravel and dark gray shale intermingled

throughout horizon. Many fine roots present.

Condition of pile:

251.5 to 246.0 ft: Many scattered pits up to 50

mils in depth. Seven pits measured between 68 and

80 mils, and two pits 88 and 122 mils in depth.

Pits were of similar depth on both sides of the pile,

but much less numerous on the side facing the

spillway. About 50 percent of the mill scale was

intact on the spillway side and 10 percent on the

other side. The reduction in cross section of the

three most corroded areas measured between 6 to 8

percent of the original wall thickness.

246.0 to 244.0: No measureable pits beyond the

thickness of the mill scale (8 mils) were found in this zone. About 50 percent of the mill scale was intact

in this area. 244.0 to 237.5: About 75 percent of the mill scale was present over the surfaces in this zone. No

measurable pits were found except two at elevation

241.0 ft which were 13 mils in depth. The average

wall thickness of a 17 X 22 in. section removed from

this zone was 0.37 in. after cleaning by sandblasting.

Sections of the pile which were exposed to the fill and natural soils are shown in figure 3.

e. Sardis Dam Outlet, Sardis, Mississippi

Hiatory:

A 3.5 ft length of steel sheet piling was cut from a length of pile pulled from the Sardis Dam Outlet

channel on the Little Tallahatchie River near Sardis,

Miss. The arch-type pile had a driving width of 19% in. and a wall thickness of % in. Date pile driven: Early 1939

Date pile pulled: October 1959

Age of piling: 20.5 years

Filing exposed: Elevation 190.5 to 187 ft Surface elevation: 194.5 ft Water table elevation: Above 194,5 ft. Soil characteristics: 194.5 to 190.5 ft: Riprap fill. 190.5 to 189.5: Gravel bed.

189.5 to 187: Black lignitic clay with layers of

sand.

Soil resistivity and pH

Elevation

190.

187.

ft

Resistivity

Ohm-cm

610 (Laboratory)

1,690 (Laboratory)...

pH

3. 0

2. 9

8-8
Condition of piles:

Metal attack occurred in the form of uniform

corrosion and general pitting over most of the surface. The section exposed to the gravel bed above

elevation 189.5 ft showed a 19 percent reduction in cross section, and maximum depth of pitting up to 60 mils. The average thickness of the pile section

exposed to lignitic clay below elevation 189.5 ft was

reduced by 11 percent; the pit depths ranged up to 30 mils.

f. Chef Menteur Pass, New Orleans, Louisiona

History: In connection with construction work on the

Simpson-Long Bridge across Chef Menteur Pass on

U.S. Highway 90, about 11 miles west of New

Orleans, it was necessary to pull about 60 tons of sheet steel pilings. The pilings formed a retaining

wall for the abutment of the bridge. The sheet pUes were 33 ft in length, arch type with a driving width

of 19% in., and a thickness of % in. at the center of

the web.

Date piles driven: 1929

Date piles pulled: 1961

Age of piling: 32 years

PUing exposed: +6 to —27 ft: Water side, +6 to 4-3 ± 1 ft in atmosphere; -|-3± 1 ft to 0 ft (mud line) in brackish salt water. SoU side, +6 to +4 ft in atmosphere; ground line at -|-4 ft. Soil characteristics:

-)-4 to —4 ft: Light gray loose sUty sand.

—4 to —27: Very tight gray clay.

Soil resistivity and pH

Elevation

ft -3—--.

-10

-24

Resistivity

Ohm-cm

440 (Laboratory)

300 (Laboratory)

330 (Laboratory)

pH

7. 8

6. 9

7. 4

Condition of piles:

Detailed examination of four lengths of pilings

showed that the degree and pattern of corrosion were similar. The condition of the pile exhibiting

the maximum amount of corrosion is reported herewith. Both sides of the top 4 ft sections of the piles were coated with a protective aluminum-type paint

and an undercoat of red lead. Water side: +6 to -1-4 ft: Paint was intact, unaffected by

corrosion.

-|-4 to -\-2: Rust and slight metal attack, two pits

measured 23 and 38 mils in depth, other pits about

10 mils.

-1-2 to 0: Thick crust of corrosion products on

the finger interlock edge between 25 and 40 mils

thick, localized pitting and metal attack beneath

the crust, some pits between 40 and 50 mils in depth.

Thin layer of corrosion products on flanges, web

and thumb interlock with pitting less than 10 mils

in depth, except for a few pits between 25 and 60 mils on one side of the flange at 1 ft. Mill scale almost

completely removed from this zone. 0 to —1: Metal attack and slight pitting (less than 10 mils) on interlock only. — 1 to —14: Mill scale intact over 95 percent

of surface. Flanges and webs unaffected by corrosion. Slight metal attack and three scattered pits

(maximum depth, 70 mils) on finger interlock at -11 to -12 ft. — 14 to —17: Metal attack and 6 pits ranging in depth between 60 to 145 mils along finger interlock.

Two pits (65 and 70 mils) on thumb interlock. No

measureable pits on web or flange. Mill scale intact over 80 percent of surface. — 17 to —19: Slight metal attack, mill scale intact over 80 percent of surface. — 19 to —20: Mill scale intact over 75 percent of

surface.. Four pits between 33 and 88 mils in depth on the thumb interlock and flange; two pits, 95 and

58 mils in depth, on other flange. —20 to —27: Mill scale intact over 90 percent of surface. Only two measurable pits, 80 and 104 mils

in depth, at —26 ft on finger interlock.

Soil side: +6 to +4 ft: Uniform thin layer of rust, no

measureable pits. -f 4 to 0: Uniform layer of rust and scale over

surface to a thickness of 40 mils. No measureable

pits.

0 to —27: Metal attack in many areas. About

75 percent of surface covered with mill scale. No

measurable pits greater than 10 mils except at elevation —24 ft where a few pits were found on the

finger interlock of one pile. Maximum pit depth,

25 mils.

g. Wilmington Marine Terminal, Christiana River, Delaware

History:

Four hundred and thirty two uncoated steel interlocking-arch-type piles, with a driving width

of 19% in. and an average web thickness of % ill- were pulled by the Wilmington Harbor Commission

from a pile jetty which was used as a shoring along

the banks of the Christiana River. The piles were

pulled in preparation for extension of the dock.

The piles were 60 and 100 ft in length. Each ninth

pile was driven 100 ft to serve as an anchor. The

100 ft piles consisted of a 60 ft section welded to a 40 ft section.

Date piles driven: 1937

Date piles pulled: 1960

Age of piling: 23 years

Piling exposed: Elevation +10 to -90 ft for 100 ft lengths; +10 to —50 ft for 60 ft lengths. River

side, top 10 ft of pile exposed to water or atmosphere.

Land side, top 4 ft of pile exposed to water or atmosphere.

9-9
Soil characteristics: +6 to 0 ft: Cinder fill. +2 to +1: Water table at low tide. River water

is nonbrackish fresh water. Mean low water at 0

ft. 0 to —48: Soft black organic silt. —48 to —86: Black organic silt with some fine sand and clay intermingled. — 86 to —88: Fine brown silty sand, trace of mica. — 88 to —91 : Clray to brown coarse sand and river

gravel. — 91 to — 1J4: Sand and silty sand underlain by

clay.

Condition oj piles:

Seven full lengths and the interlock edges of 70

piles were inspected. All the piles were in excellent

condition from the mud line (elevation 0 ft where the

natural soil starts) down to the bottom of the piles.

The piles are to be reused in the new dock structure

at the same site. + 10 to 0 ft: Moderate corrosion on surfaces

exposed to water and the atmosphere on the river

side, and to cinder fill, water and atmosphere on the

land side. Surfaces were imiformily corroded, the

original thickness of the piles being reduced by an

average not exceeding 10 percent. Widely scattered

pits present; most of the pits had depths less than

75 mils, but a few had depths between 75 to 150

mils.

0 to bottom of piles: Accumulation of slick clay over most of the surface. No measurable pits.

Mill scale intact over more than 90 percent of the

surfaces.

h. Lumber River Near Boardman, North Carolina

History:

The North Carolina State Highway Department

extracted 120 piles which formed a rectangularshaped cofferdam for a bridge support over the

Lumber River near Boardman, N.C. The structxu-e was removed in connection with road improvements

which required replacement of the old bridge.

The steel piles were 20-ft lengths of interlocking

I-beams having a driving width of 8 in. and a wall

thickness of 0.25 in. The corners of the cofferdam

consisted of steel angles to which interlock sections

of pilings were attached by steel rivets, spaced 9 in. apart.

Date piles driven: 1921

Date piles pulled: December 1958

Age qf piling: 37 years

Piling exposed: 2.5 ft above ground to 17.5 ft below

the ground line (+2.5 to —17.5 ft). The portion of

the piles above the ground line was subjected to

partial or total immersion from water of the Lumber

River about 50 percent of the year, and to the

atmosphere when the river was dry during the

remaining half year. The sides of the pilings which

were exposed to the excavated side of the cofferdam were in contact with concrete, except fort he bottom

3 ft which was entirely siu"rounded by soil.

Soil characteristics: 0 (ground line) to —8 ft: Gray fine sandy loam. —8 to —14: Bluish-gray plastic silty clay. — 14 to —17.5: Gray-black fine sandy loam containing appreciable gravel.

Soil resistivity and pH

Elevation

-3-10-

-16

Resistivity

Ohm-cm

1, 240

1, 100

4, 900

pH

.3. 4

2. 3

.5. 9

Condition of piles:

Visual inspection of the pilings revealed thati they

had all corroded to about the same extent. A

section of the cofferdam consisting of two full lengths of piles and a corner angle was shipped to the laboratory for further examination.

Practically no mill scale remained on the pile

surfaces in the zone extending from 3 ft below the

ground line to the top of the piles. In the lower zones, approximately 20 percent of the mill scale was

intact.

Thin concrete deposits were found on the surfaces

where the steel had been in contact with concrete on the excavated side of the cofferdam. There was

a thick scale of rusted corrosion products and soil over the entire surface exposed directly to the soil environments. The scale was flakey and easily

removed by scraping.

The following conditions were observed after the piles were cleaned by sandblasting:

+ 2.5 to 0 ft: Section exposed to total or partial

water immersion, or atmosphere. Uniform corrosion

of surface. Measm-ements of the cross section in the top 6 in. of the piles (elevation +2.5 to +2.0)

showed a minimum thickness of 0.06 in. in places.

This represents a loss of 76 percent in the original

pile thickness. The maximum thickness measured

on uncorroded sm'faces near the bottom of the piles was 0.26 in. Piles in the zone between +2.0 ft to the ground line showed a maximum reduction in thickness of 60 percent.

0 to —0.5: This area showed an amount of cor- rosion similar to that on the adjacent areas above.

The original pile thickness in this zone was reduced

by a maximum of 40 percent, and isolated pits ranged

in depth up to 60 mils. —0.5 to —1.0: The pattern of corrosion in this zone was similar to that noted above. Maximum

reduction in pile thickness was 36 percent. — 1.0 to —3.0: Uniform corrosion, general roughening of surface, numerous shallow pits and many

isolated pits up to 60 mils. Maximum reduction in cross section was 28 percent. —3 to —17.5: In this zone the condition of the

surface was similar to that described above, but was

less severely corroded. Many isolated pits measured

up to 30 mils in depth, and relatively few up to 60

10-10
mils. A maximum reduction in pile ciuss section of 12 percent was noted in this zone. The corner angle along the entire piling section

showed the same extent of corrosion as the I-beams.

All rivets were uniformly corroded. The original

contoiu" of the rivets was intact.

A 3-ft corner section of the piling exposed immo-

(liately below the soil line is shown in figure 4.

4.2. Pilings Exposed in Excavations

a. Memphis Floodwall, Memphis, Tennessee

History:

Excavations were made to expose pilings at two

locations on the river side of the Memphis Floodwall.

The walls consist of type Z 27 sheet pilings having

an 18-in. driving width, and a thickness of %-ixi. at

the web and flanges. The pilings at station 56+14

were given two coats of cold applied coal-tar-base

enamel before driving, and the piUngs at station

60+00 were uncoated.

Date piles driven: November 1953

Date oj inspection: March 1960

Age oj piling: 6.3 years

STATION 56+14

Piling exposed: An 8-ft width of the floodwall was

exposed between elevation 223.0 to 216.5 ft. Surface elevation: 228 ft Water table elevation: 217.5 ft Soil characteristics: 228 to 223 ft: Friable brown lean clay.

223 to 221.5: Plastic and friable gray silty clay.

221.5 to 217.5: Plastic light brown clayey silt. Excessive water below 219.5 ft. 217.5 to 216.5: Tight gray clay mixed with decomposed wood.

Soil resistivity and pH

Elevation

ft 228 to 218

228 to 208.

228 to 198

223 222

221

221

219.5 219

218

216.5

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Ohm-cm

1,220 (4-pin)

8,600 (4-pin)

4,400 (4-pin) _

960 (4-pin).

6,900 (4-pin).

2,600 (4-pin)

1,030 (4-pin) _ 3,400 (4-pin).

1,850 (4-pin) _

1,900 (Shepard Canes)

3,100 (Shepard Canes).

2,240 (Laboratory)

2,300 (Shepard Canes)

1,700 (Shepard Canes)

1,410 (Laboratory)

2,200 (Shepard Canes)

1,000 (Shepard Canes).

pH

7. 8

'7.'

Condition oj piles:

The coal tar coating was intact over the entire

surface except at elevation 220.5 to 219.5 ft where

the coating was damaged in an area 1-ft in vertical

direction by 1-in. in width. The maximum depth of

pitting of the steel exposed by the damaged coating was 35 mils (fig. 5). The steel beneath the rest of

the coating was unaffected by corrosion and the mill

scale was intact.

STATION 60+00

Piling exposed: An 8-ft width of the floodwall was

exposed between elevation 222.5 and 213.5 ft. Surface elevation: 226.5 ft Water table elevation: Below 213.5 ft Soil characteristics: 226.5 to 224 ft: Brown lean clay.

224 to 222.5: Gray silty clay.

222.5 to 218.5: Friable brown silty clay. Some

cinders mixed with the clay between 223 and 220 ft. 218.5 to 213.5: Friable and plastic reddish browm

silty clay. Very impervious to water.

Soil resistivity and pH

Elevation

ft 226.5 to 216.5

226.5 to 206.5

226.5 to 196.5

222

221

221

219.5 218.5 217 214

213.5

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Ohm-cm

2,180 (4-pin).

5,700 (4-pin).

4,100 (4-pin) _

1,920 (4-pin).

7,900 (4-pin).

4,200 (4-pin).

1,030 (4-pin).

2,300 (4-pin).

1,650 (4-pin).

3,200 (Shepard Canes)

2,500 (Shepard Canes).

2,200 (Laboratory)

2,600 (Shepard Canes).

2,100 (Shepard Canes).

1,690 (Laboratory)

1,630 (Laboratory)

1,500 (Shepard Canes).

pH

6. 8

7. 8

7. 5

Condition oj piles:

The entire surface of the pilings was in excellent

condition. More than 90 percent of the mill scale was intact. There was very slight uniform metal

attack in small localized areas. No measm-able pits were found on the entire surface. From elevation

218 to the bottom of the excavated pit, the clay

adhered very tightly to the piling. On removal,

the soil peeled off in layers leaving free water on the

steel surface.

A 2 ft by 1 ft section removed from the pile is shown in figure 5. 11-11
. rt-W-h

Figure 4. A S-ft section of steel sheet piling exposed below the soil line in a cofferdainlstructure in the Lumber

River near ^Boardman, North Carolina.

Exposure, 37 yeais.

b. Vicksburg Floodwall, Vicksburg, Mississippi

History:

Excavations were made to expose steel sheet

pilings at two locations on the riverside of the

Vicksburg Floodwall. The walls were constructed

of type Z 38 sheet piling which has a driving width

of 18 in., a thickness of ji in. at the web, and a thick- ness of H in. at the flanges.

Date piles driven: January 1953

Date of inspection: March 1960

Age of piling: 7.2 years

STATION 16+32

Piling exposed: A 38-in. width of the floodwall was

exposed between elevation 89 and 80.5 ft. Surface elevation: 93 ft Water table elevation: 80.5 ft Soil characteristics: 93 to 86 ft: Bluish black fat clay, sticky, plastic,

and very retentive of water. Small patches of red

and yellow sand dispersed throughout the profile.

86.0 to 85.5: Black silty plastic clay, containing more than 50 percent cinders.

85.5 to 84.5: Light brown sandy loam with cinders

and gravel dispersed throughout.

84.5 to 84.0: Layer of black cinders.

84.0 to 80.5: Gray sandy silt containing cinders.

Wet cinders on floor of excavation at 80.5 ft.

Figure 5. Steel sheet piling sections {2 ft by 1 ft) cut from two

locations on the Memphis Floodwall after exposure for 6.3

years. The sections were cleaned by sandblasting. AlOl, section of poated pilingshowing pits up to 35 mils in depth, occurring in area of damaged coating. A102, section of uncoated piling exposed to a silty clay containing cinders showing no measureable corrosion.

Soil resistivity and pH

Elevation

93 to 83_

ft

93 to 73

_

93 to 63.

88

88 to 87.

85

83

82.5

82 to 80.

80.5

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Min

Max

Min

Max

Min

Max

Min

Max

Ohm-cm

3,400

7,000

6,000

2,200

4,300

3,300

920

2,400

1,550

4-pin).

4-pin)

4-pin).

; 4-pin)

; 4-pin)

[4-pin)

4-pin)

'4-pin).

'4-pin)

1,190 (Laboratory)

850

1,300

1,700

2,500

2,500

1,750

1,550

4,000

850

1,400

(Shepard Canes)

(Shepard Canes)

Shepard Canes)

Shepard Canes)

Laboratory)

Laboratory)

(Shepard Canes)

(Shepard Canes)

(Shepard Canes)

(Shepard Canes)

pH

7. 4

7. 6

8. 2

12-12
Figure 6. Sandblasted sections of Z-type sheet piling cut from

two different locations in the Vicksburg Floodwall after exposure for 7 years. Although cinders were present in the soil at both locations, no significant cor- rosion occurred. BlOl, Section removed from floodwall at station 16+32.

B102, Section removed from floodwall at station 23+83.

Condition of piles:

Approximately 30 to 40 percent of the steel surfaces was covered with mill scale. Soil adhered in many

areas of about 1-in.^ like barnacles, beneath which

appeared uniform metal attack or shallow pitting.

Pitting up to 40 mils in depth was widely scattered

and confined to areas of less than 1 in.^ At elevation

83.5 to 81.5 ft, there were a few pits with depths

between 40 and 45 mils. Measurements made on

the three most corroded 1 in.^ areas showed an aver- age reduction in the cross section of the web of 4 to 6 percent. A section removed from the most corroded

area of the pile is shown in figure 6. STATION 23+83

Piling exposed: A 41 -in. width of the floodwall was

exposed between elevation 89 and 80.5 ft. Surface elevation: 93 ft Water table elevation: 80.5 ft

Soil characteristics: 93 to 84 ft: Bluish-gray clay with nodules of brown

clay dispersed throughout.

84 to 83.5: Plastic and sticky light brown to reddish brown clay containing some cinders.

83.5 to 80.5: Dark gray silty sand mixed with

appreciable quantities of cinders, gravel, stones, and

bricks. Tbis horizon appears to be a fill material.

Free water at bottom of trench.

Soil resistivity and p\i

Elevation

!>:i to 83.

fi

i)!} to 7:i__..

m to 6:i.._.

89 to 84___.

88.5

83.5 83

81

83.5 to 80.5

Resistivity

Mill Max

Avg

Mill Max

Avg

Mill Max

Avg

Min

Max

Avg

Ohm-cm

2,800 (4-pin).

9,200 (4-pin).

5,000 (4-i)in).

1,300 (4-pirO.

3,700 (4-pin).

2,800 (4-pin).

740 (4-pin).

2,000 (4-pin).

1,400 (4-pin).

625 (Shepard Canes)

825 (Shepard Canes) 725 (Shepard Canes)

910 (Laboratory)

1,700 (Shepard Canes).

3,900 (Laboratory)

1,050 (Laboratory).

Min

Max

Avg

1,100 (Shepard Canes).

1,400 (Shepard Canes).

1,300 (Shepard Canes).

pH

7. 1 a 6

Condition oj piles:

Mill scale was intact on about 70 percent of the

piling surfaces. There was no difference in the

appearance of the surface at the different horizons.

Where the mill scale had been removed, there was a

film of red rust which was brushed off with ease. Under the rust, the steel surfaces were smooth. No

measureable pits were found on the exposed pilings.

Measurements fail to show a perceptible reduction in wall thickness (fig. 6).

c. Sardis Dam Spillway, Saidis, Mississippi

History:

An excavation was made to expose a 7-ft width

of pilings from the upstream wingwall on the east

side of the Sardis Dam SpUlway. The structure

consisted of arch-type sheet piles with a 15-in. driving width and a wall thickness of % in. Date piles driven: Early 1940

Date oj inspection: March 1960

Age oj piling: 20 years

Piling exposed: A 7-ft width of the wingwall was

exposed from elevation 307 to 302 ft. Surface elevation: 312 ft Water table elevation: 305 ft Soil characteristics: 312 to 305 ft : Fill soil consisting of uniform reddish

sandy loam.

305 to 302: Natural soil, reddish brown tight

impervious plastic clay.

13-13
Soil resistivity and pH

Elevation

312 to 302

312 to 192

312 to 182

312

310

306

303

302

302

Resistivity

Ohm-cm

Min. 43,600 (4-pin).

_

Max. 50,200 (4-pin)

Avg. 46,500 (4-pin)

Min. 29,100 (4-pin) _ Max. 36,000 (4-pin) _ Avg. 32,800 (4-pin) _

Min. 23,800 (4-pin).

Max. 29,300 (4-pin).

Avg. 26,000 (4-pin).

> 10,000 (Shepard Canes)

> 10,000 (Shepard Canes)

15,400 (Laboratory)

>4,000 (Laboratory)

7,510 (Laboratory)

3,000 (Shepard Canes) .

pH

5. 7

6. 0

5. 4

Condition of piles:

Mill scale was intact over approximately 90 per- cent of the pile surfaces. In localized areas, which

were predominant in the top 8-in. section of the

pUes, there was slight metal attack and shallow

pitting, not exceeding 10 mUs in depth. In an

area covering a width of about 2 ft between elevation 304 and 302.5 ft, there were isolated pits which

measured between 10 and 20 mils in depth, and

three pits between 20 and 28 mils. The average

reduction in pile thickness measured in the three

most corroded areas in this zone was between 3 and

4 percent.

d. Grenada Dam Spillway, Grenada, Mississippi

History:

Two excavations were made to expose steel sheet

pilings for examination on the north side and the

south side of the upstream wingwalls of the Grenada

Dam Spillway on the Yalobusha River. The pilings

consisted of the arch-sheet type with a driving width

of 15 in. and a wall thickness of % in. Date piles driven: October 1948

Date of inspection: March 1960

Age of piling: 11.4 years

UPSTREAM WINGWALL—NORTH SIDE

Piling exposed: A 6.7 ft width of the wingwall was

exposed between elevation 251.5 and 246 ft. Surface elevation: 256 ft Water table elevation: Much below 246 ft Soil characteristics: 256 to 246 ft: Fill material consisting of friable

reddish brown clayey sand or silt loam with clods

of grayish sandy clay and patches of very fine yellowish brown sand throughout the pit. Gravel, stones,

pieces of dark gray shale, and fine roots present.

Soil resistivity and pH

Elevation

ft 256-246...

256-236...

256-226...

255

249

247

246

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Ohm-cm

12,500 (4-pin).

16,500 (4-pin).

13,900 (4-pin).

4,700 (4-pin)..

9,600 (4-pin).

6,900 (4-pin)..

4,300 (4-pin).

7,200 (4-pin).

6,200 (4-pin).

9,000 (Shepard Canes)

2,400 (Laboratory)

2,300 (Laboratory)

1,700 (Shepard Canes).

3,500 (Shepard Canes)

2,400 (Shepard Canes)

pH

4. 4

4. 0

Condition of piles:

Mill scale was intact on about 20 percent of the

pile surfaces. Approximately 60 percent of the sur- face was uniformly corroded to shallow depths and

contained many scattered pits which generally

ranged in depth between 40 and 90 mils. A few

pits between 90 and 108 mils in depth were present.

The. deepest pits were mainly concentrated between

elevation 248 and 247 ft. The deeper pits were

highly localized and were found under nodules of soil particles which appeared to be cemented to the steel and were difficult to scrape away. Measm-ements of

the three most corroded areas showed average re- ductions in the thickness of the piles of 16, 13, and 10

percent.

UPSTREAM WINGWALI^SOUTH SIDE

Piling exposed: A 7-ft width of the pilings in the

wingwall was exposed between elevation 251.5 and

246 ft. Surface elevation: 256 ft Water table elevation: Much below 246 ft Soil characteristics: 256 to 248 ft: Reddish brown fine sandy loam with

clods of light gray clay dispersed throughout the

profile. This is a fill soil containiag many fine roots. 248 to 246 : Mixture of fine rust colored very fine light yellow sUty sand intermingled with pieces of

light gray shale.

Soil resistivity and pH

Elevation

.n 256 to 246.

Resistivity

Min

Max

Avg

Ohm-cm

5,900 (4-pin).

8,000 (4-pin).

7,000 (4-pin).

pH

14-14
Soil resistivitj' and pH—Continued

Elevation

ft 256 to 236_

256 to 226_

250_-.

248.5.

247_..

246.

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Alax

Avg

Ohm-cm

3,400 (4-pin).

6,900 (4-pin).

4,300 (4-pin).

2,700 (4-pin).

3,800 (4-pin).

3,500 (4-pin).

2,400 (Laboratory).

4.000 (Laboratory).

4,300 (Laboratory).

5,000 (Shepard Canes)-.

11,000 (Shepard Canes).

7,900 (Shepard Canes) .

pH

4. 4

6. 4

6. 9

Condition of piles:

251.5 to 248 ft: Mill scale was present over 70

percent of the surface. Many highly localized pits

corroded about 15 percent of the surface, the re- maining 85 percent of the surface was unaffected by

corrosion. SLx pits were found between 100 and 172

mils in depth, eight pits between 50 and 95 mils, and

other pits measured less than 50 mils. The corrosion

products and soil particles adhering to the steel in

this zone were easily scraped off. 248 to 246 : About 30 percent of the piling surfaces were affected by scattered pits, the other areas being

unaffected by corrosion. SlSl scale was intact over more than 50 percent of the surface. The seven

deepest pits ranged between 105 and 160 mils in depth. Also present were 11 pits between 50 and 95

mils and other pits less than 50 mils in depth. The

average reduction in wall thickness measured in the

three most corroded areas was between 12 and 19

percent. In this zone, the soil particles were easily

scraped from the steel surfaces, but a black crust of

ferric o.vide which was embedded in the pits was

difficult to break away.

e. Berwick Lock, Berwick, Louisiana History:

Two excavations were made to expose steel pilings

in the cutoff walls on the west side and east side of

the north end of the Berwick Lock which is located

between the Lower Atchafalaya Eiver and Berwick

Bay near Ber^vick, La. The arch-type sheet steel pilings had a driving width of 19% in. and a ji in. wall thickness.

Date piles driven: March 1949

Date oj in^spection: April 1960

Age oj piling: 11.1 years

XOETH END OF LOCK—WEST SIDE

Piling exposed: A 5-ft ^ndth of pilings was exposed

between elevation +3.5 to —1.5 ft. One side of the

pilings which was uncoated, was totally exposed to the soil environment. The other side of the pilings

had a coal tar coating and was exposed to water. Surface elevation: + 5 f

Water table elevation: —0.5 ft Soil characteristics: + 5 to + 2 ft: Fill material consisting of a mixture

of gray and brown silty clay containing some gravel

and small shells. + 2 to — 1.5: Natural soU consisting of tight bluish

gray impervious plastic clay with patches of tight

brown clay dispersed throughout the profile.

Soil resistivity and pH

Elevation

-5 to

•5 to —15-

-f 5 to —25.

+4-

2__.

2__.

1...

0_..

-1.5.

Resistivity

Min

Max

Avg

Ohm-cm

860 (4^pin) .

960 (4-pin) . 900 (4-pin) _ Min 990 (4-pin)

Max 1, 260 (4-pin)

Avg 1, 190 (4:-pin) Min 1, 380 (4-pin)

Max 1, 550 (4-pin)

Avg 1, 440 (4-pin)

Min 680 (Shepard Canes).

Max 950 (Shepard Canes).

-\vg 820 (Shepard Canes).

1, 000 (Shepard Canes).

1. 400 (Laboratory)

1, 290 (Laboratory-)

850 (Shepard Canes).

800 (Shepard Canes).

850 (Shepard Canes).

8. 5

8. 1

Condition of jpiles: -r-3.5 to —1.5 ft: Mill scale was intact over 40

percent of the surface. The remaining surface was

uniformly attacked and had many shallow pits less than 25 mils in depth, and some deeper pits. A

few pits ranged between 55 and 61 mils in depth,

and many others ranged between 25 and 55 inils. The average reduction in wall thiclcness observed on

the three most corroded areas was between 6 and 8

percent.

-f 1.5 to —1.5 ft: Mill scale was intact over about

60 percent of the surface. Slight imiform corrosion was present on the remaining surface and there were many pits which did not exceed 25 mils in depth.

There was sHght general metal attack and pitting over the entire coated side of the pilings which was

exposed on the water side. The river water had a

resistivity of 2,500 ohm-cm, and a salt content of

40 ppm.

NORTH END OF LOCK—EAST SIDE

Piling exposed: A 5 ft width of the wall was exposed

between elevation +3.5 and 0 ft. Surface elevation: + 5 ft Water table elevation: + 1 ft Soil charad-eriMics:

+ 5 to + 3 ft: Fill consisting of a mixture of slightly

15-15
friable reddish brown and gray tight clay containing

gravel and many stones. + 3 to 0: Natural soil consisting of brown fat plastic clay.

Soil resistivity and pH

Elevation

ft + 5 to —5-

+ 5 to -15

+ 5 to —25

+ 4

+ 2.5 + 1.5 + 1

0

Resistivity

Min

Max

Avg

Ohm-cm

960 (4-pin)

1, 280 (4-pin)

1, 130 Min 1, 150. Max 1, 530. Avg 1, 370- Min 1,210.

Max 1, 610. Avg 1, 480. Min

Max

Min

Max

Min

Max

950 (Shepard Canes).

1, 300 (Shepard Canes)

1,050 (Laboratory).

1, 220 (Laboratory).

870 (Shepard Canes).

1, 000 (Shepard Canes).

750 (Shepard Canes).

1, 200 (Shepard Canes).

8. 1

7. 9

Condition of piles:

+3 to -fl ft: Mill scale was present on 40 percent

of pile- surfaces. There was uniform corrosion

and pitting where the mill scale was missing. The

tliree deepest pits were between 75 and 90 mils in depth. About 30 pits measured between 20 and

75 mils in depth, and many other pits were shallower

than 20 mils. The average reduction in pile thick- ness observed in the three most corroded areas was between 8 and 11 percent.

-fl to 0: About 75 percent of the mill scale was

intact in this zone. The pile surfaces were smooth,

had little metal attack, and all pits were less than 20 mils in depth.

The condition of the coated piles exposed to the

water side was similar to that described for the

piling on the west side of the lock.

f. Algiers Lock, New Orleans, Louisiana History:

An excavation was made to expose type Z 32 sheet

pilings in the cutoff wall on the east side of the

south end of Algiers Lock, which is located on the

Algiers Canal at the Mississippi River, New Orleans,

La. The piles have a driving width of 21 in. and

wall thicknesses of Ys in. at the web and in. at the

flanges.

Date piles driven: May 1948

Date of inspection: April 1960

Age of piling: 11.9 years

Piling exposed: A 5-ft width of the cutoff wall was

exposed between elevation -f 3.5 to +1 ft

Surface elevation: -f 5 ft Water table elevation: -f 2 ft Soil characteristics: +5 to 3.5 ft: Brown silty clay fill material.

+3.5 to -fl: Brown silty clay with pockets of

tight plastic grayish blue clay dispersed throughout

the profile with large quantities of organic matter,

rotted wood, gravel, and small stones.

Soil resistivity and pH

Elevation

ft + 5 to -5-.

+ 5 to -15

+ 5 to -25

+ 5

+ 3

+ 2

+ 1

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Min

Max

Min

Max

Ohm-cm

800 (4-pin).

840 (4-pin).

820 (4-pin).

575 (4-pin).

650 (4-pin)

600 (4-pin)

345 (4-pin)

460 (4-pin). 410 (4-pin).

700 (Shepard Canes).

1, 150 (Shepard Canes).

1, 300 (Shepard Canes).

1, 140 (Laboratory)

1, 290 (Laboratory)

650 (Shepard Canes).

1, 200 (Shepard Canes).

1, 300 (Shepard Canes).

8. 4

7. 7

Condition of piles:

Mill scale was present over approximately 85

percent of the surface. Nodules of clay adhered

to the steel surface in scattered small areas, generally not exceeding 1 in.^ in size, beneath which were

light metal attack or pitting. The deepest pit

measured 40 mils in depth. Nine pits measured

between 22 and 32 mils in depth, and other pits

measured less than 20 mils. The average reduction

in wall thickness measured on the three most cor- roded areas of the sample pile section cut from the

wall was between 3 and 4 percent.

g. Enid Dam Spillway, Enid, Mississippi

History:

An 8-ft width of steel sheet pilings was exposed on

the north side of the upstream wingvvall in the Enid

Dam Spillway. The piles consisted of interlocking

arch-type beams having a driving width of 18 in. Date piles driven: September 1949

Date of inspection: May 1961

Age of piling: 11.7 years

Pilmg exposed: An 8-ft width of the pilings was

e.xposed between elevation 288 and 282.5 ft. Surface elevation: 293 ft Water table elevation: Much below 282.5 ft Soil characteristics:

293 to 290.5 ft: Brown silty clay, somewhat

plastic.

16-16
290.5 to 282.5: Reddish brown coarse sand con- taining much silt and gravel.

Soil resistivity and pH

Elevation Resistivity

ft 293

290.5 288

284

282

282.5

Ohm-cm

8,500 (Shepard Qanes).

8,000 (Shepard Canes) _ 10,000 (Shepard Canes)

>4,000 (Laboratory)..

10,200 (Laboratory)...

9,500 (Shepard Canes)

pH

5. 1

5. 3

Condition of piles:

Mill scale was intact over more than 90 percent

of the surface. Slight metal attack was present in a few small areas, approximately 1 in. in diameter.

There were no measurable pits.

5. Discussion

Previous investigations on soil corrosion conducted

by the National Bureau of Standards have been

restricted to the behavior of metals in disturbed

soUs; trenches or excavations were dug and backfilled after installation of the specimens. Because no prior systematic investigation pertaining to the

behavior of metals in undisturbed soils had been

conducted, it became general practice because no

other data were available to apply the information

provided hy the NBS soil investigations as a guide

to estimate the corrosion of metals in all types of

underground iastallations, under both disturbed and

undisturbed soil conditions.

The findings of the National Bureau of Standards

with respect to the action of soils on metals have

been presented on numerous occasions in various

ways, and more recently assembled in the National

Bureau of Standards Circular 579 [1]. The following repetition of the pre\4ously obtained major conclusions pertaining to the corrosion of iron and steel

is not for the purpose of imparting new information,

but to establish a basis for discussion of the data

obtained from the piling inspections.

Briefly, the Bureau has found, first, that the

corrosion of the commonly used ferrous metals is of

the same type and order of magnitude when exposed

to a given soU environment; and second, that the

corrosion of ferrous metals in different soil environments varies widely. In general, in well-drained

high-resistivity soils, the rate of corrosion may be

high initially, but decreases after a few years to almost complete cessation of pitting. Conversely,

in poorly drained soils ha%"ing low resistivities, the

rate of corrosion is nearly constant with time after the initial period.

One of the most interesting characteristics of

underground corrosion is the irregular nature of the

attack. A section of pipe is often penetrated at only one or more points and practically no corrosion is found elsewhere on the section. Usually, the loss

of ferrous metal is too small to be of importance if

it were uniformly distributed over a metal surface.

The major cause of corrosion can be attributed to the nonuniformity in the distribution of oxygen and

moisture along the surface of a buried metallic

structure. Variations in the supply of oxygen can

set up oxygen-concentration cells in which the metal

surfaces which are least accessible to oxygen are anodic to the surfaces to which oxygen is more

readily accessible. The corrosion may be either general or localized depending upon the relative size of

the anodic and cathodic areas. For a given difference

in potential between the two areas, if the anode area

is relatively large compared to the cathode area, the

total current produced may be small or negligible and

the little damage to the anode area will be distributed over an appreciable area in the form of uniform cor- rosion. On the other hand, if the anodic area is relatively small compared to the cathodic area, the

corrosion is localized and severe damage may result

due to penetration of the metal by pitting.

The pitting type of corrosion is of major importance in pipe lines or other structures designed

to carry liquids or gas. On the other hand, for underground structures that are primarily loadbearing the depth of pitting is of less interest than

the overall loss in weight or strength. Hence, in relating corrosion damage to the useful life of piling

the most important measurement involves the

amoimt of uniform corrosion that will result in a reduction of the cross section.

The data from 19 installations listed in section 4

provide information on the behavior of steel pilings

to depths of 136 ft and for exposures of 7 to 40 yr in a wide variety of soil conditions. The data are summarized in table 3 to facilitate interpretation and

to bring out any relationship that may exist between

the corrosion observed on the pilings and the characteristics and properties of the soils. Fill material which varied in content from riprap,

cinders, slag, and combinations of sand, silt, loam,

and clay was present at nine locations above the

water table. The undisturbed natural soils covered

a range from well-drained sands to impervious tight

clays. The resistivities of the soils ranged from 300

ohm-cm (indicating the presence of large quantities

of soluble salts)" to 50,200 ohm-cm, (indicating the

absence of soluble salts). The jiH of the soil ranged

from 2.3 to 8.6. Any attempt to estimate the corrosiveness of the

soils to which the pilings were exposed by association of the soil properties and characteristics with

data obtained from similar soil environments from

either NBS field tests, or actual service history of structm-es in disturbed soils, could only lead to the

expectation of severe corrosion at most of the sites. Skipp [15] suggested that engineers make a thorough

site investigation in designing structures utiUzing

buried steel piles in order that due allowance may

be made for corrosion and its prevention. The in- vestigation procedures he recommended to determine the likelihood of corrosion and its possible

severity are essentially those used to predict corro17-17
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Figure 7.

Electrode

Electrode

Corrosiveness of soil samples from Bonnet Carre Spillway as indicated by electrode weight losses after 6 months in modified Denison corrosion cells.

sets A and C set up under aerated and unaerated conditions, respectively, with soil samples obtained at 22 ft depth from surface of ground,

sets B and D set up under aerated and unaerated conditions, respectively, with soil samples obtained at 45 ft depth.

Electrode Ixjss in weight

A

ozlft' 2.03

1.82

0. 064

0. 15

B

CD

sion of structures, such as pipelines, in disturbed

soils. Emphasis was placed on survey methods

involving measurements of pH, soil electrical resisti- vity, redox potential, and bacterial activity. It is evident from an evaluation of the data in

table 3 that the survey methods recommended by

Skipp, which presently are the methods widely used

by engineers, are misleading in that they over- estimate the corrosion of steel pilings driven in soils. For example, the 122-ft length of H-pile pulled from

the Bonnet Carre Spillway after exposure for 17 yr was subjected to varying soil types at different

horizons under poorly aerated conditions. At the

time the pile was inspected, soil samples collected

from the pile walls at depths of about 22 ft and 45 ft from the surface were shipped to the National Bureau of Standards. The soils consisted of clay having

a resistivity of 400 ohm-cm and a pH between 7.8 and 8.1. Chemical analysis detected the presence of

appreciable quantities of soluble salts in the form of

carbonates, bicarbonates, sulfates and chlorides, the

latter being predominant (table 3). The properties

of this soil are nearly similar to those of a Docas clay

soil found at Site 64, one of the most corrosive soils in the NBS corrosion field tests. At this site, carbon

steel pipe specimens with a wall thickness of 0.154

in. were perforated by corrosion within 5 yr and had

large weight losses.

The soil samples from the Bonnet Carre Site were

subjected to the modified Denison corrosion ceil test in the laboratory [1,16]; by means of this cell the

behavior of U'on or steel in different soils can be

investigated under controlled conditions of moisture

and aeration. In the aerated condition, the moisture

content is controlled to make the soil suflSciently per- meable for access of oxygen to the cathode. In the

unaerated condition, all the soil is puddled at the

time of setting up the cells, thus limiting access of oxygen to- the electrodes. The small amount of oxygen available in the uilaerated cell is rapidly depleted during the initial corrosion process and the

replenishment of oxygen at the cathode becomes

difficult because of the puddled soil. An estimate of the corrosiveness of a soil is determined in the Denison cell by a measurement of the

galvanic current between the electrodes or preferably

by the combined weight losses of the two electrodes.

Good correlations were obtained between the weight

losses of corrosion cells set up for six months under

aerated conditions using soils from NBS test sites and the weight losses occurring in the field at the

test sites on wTOught ferrous pipe specimens exposed

for 10 yi- [1,16].

The results obtained with the modified Denison

cell on the Bonnet Carre soil samples for six months'

19-19
exposure in the laboratory under aerated and unaerated conditions are shown in figure 7. It was previously pointed out that the soil samples

from the piling which was extracted from the Bonnet

Carre Spillway had properties similar to those of the

severely corrosive Docas clay soil in the NBS field tests. The laboratory corrosion cell set up under the

aerated conditions produced weight losses of the same order of magnitude for the Bonnet Carre (fig. 7, A and B) and Docas clay soils [1,16] indicating

that the Bonnet Carre soil is equally as corrosive as the

Docas clay soil under aerated conditions. The

weight losses of ferrous pipe specimens which were

exposed in the disturbed soil at the Docas clay site are in relatively good agreement with the results

obtained in the laboratory under aerated conditions.

On the other hand, the piling extracted from the

Bonnet Carre Spillway after exposure for 17 yr was unaffected by corrosion at all depths below the

water table zone, and showed but a negligible amount

of corrosion in the water table zone. This is in

complete accord with the results from the laboratory

cell test which showed a relatively negligible amount

of corrosion for the cell electrodes set up under unaerated conditions as compared with that of the cell electrodes set up under aerated conditions.

The data presented in section 4 and summarized

in table 3 show that, in general, the amount of corrosion of the pilings exposed below the water

table zone at any of the sites was not sufficient to have an appreciable effect on the strength of the

pilings for the periods of exposure. The water table zone is defined as the zone lying between ±2 ft of

the water table. At Sparrows Point, a 3-ft section of each of the two

H -piles contained some moderate corrosion below

the water table at elevation of about —116 ft. These sections of the piles passed through a coarse sand and gravel bed through which ground water

flowed more freely than in the other strata. The

corrosion can possibly be attributed to the action of

dissolved carbon dioxide. The sections of the piles

above the sand and gravel stratum to the water

line zone and below the sand and gravel stratum to the bottom of the piles were almost entirely coated

with mill scale. The condition of three sections of one of the H -piles pulled from Sparrows Point is shown in figure 1. Corrosion was found on steel piles exposed below

the water table at the Sardis Dam, Chef Menteur

Pass Bridge, and the Lumber River structures. The pits were highly localized as indicated by the

large amount of mill scale intact on the pile surfaces.

Only small or neghgible reductions in wall thick- nesses were observed.

The portions of pilings which appeared to be the

most vulnerable to corrosion were the sections

exposed in fill soil located above the water table

level or in the water table zone. In the water table zone, corrosion was found on the pilings extracted

from the Sparrows Point and Lumber River locations, reductions of 29 and 40 percent were observed

in the cross sections of the piles after 18 and 37 yr.

respectively. Corrosion tapered oft" rapidly and was not appreciable below the water table zone.

Significant corrosion occurred above the water

table only in fill soils at Grenada Dam, Berwick

Lock, and at the Wilmington Marine Terminal

(table 3). The corrosion at these locations was

highly localized as shown by the reductions in waU

thickness of the piles.

Inspections of the pilings in the test holes at Grenada Dam were made early in the investigation.

The pitting type of corrosion found on the piles

exposed to the fill soil were of concern to personnel

of the Corps of Engineers. As a result, a pile

section was pulled from the north wingwall structure

to observe the condition of the pile at greater depths.

No corrosion of any significance was found in the

natural soil below the fill layer.

The data indicate that the depths of maximum

pitting give no indication of the extent of corrosion on pilings. A review of each case history in section

4 shows that the number of deep pits are relatively

few for the large areas of pile surface involved, and

that most of the measured pit depths are considerably less than the maximum reported in table 3. Furthermore, corrosion by pitting covers a rela- tively small area of the pilings, especially below the

water table zone. Significant pitting was not observed on many of the piles below the water line. An example of this is illustrated in figure 2 for the

piling pulled from the Ouachita River Lock after 40

yr of exposure.

It should also be noted that there is generally a marked difference between the maximum depth of

pitting and the reduction in cross section area. For example, maximum pit depths of the order of

145 mils found on the pihngs from the Chef Menteur

Pass Bridge might cause considerable concern for a

fluid-carrying structure regardless of the condition

of other portions of the structure. On the other

hand, because of the localized and isolated nature

of attack, pit depths of this magnitude do not have

aQ appreciable effect on the strength or useful life of pifing structures because the reduction in pile cross section after exposure for 32 yr is not significant.

At the time of driving the H -piles at Sparrows

Point and the 100-ft lengths of the sheet piles at the Wilmington Marine Terminal, sections forming

the full pile length were joined by butt welds. The

welds showed no evidence of corrosion at the time

of inspection after the piles were pulled. A welded

joint on the Sparrows Point pile is shown in figure 1. Stray currents have been detected and measured

throughout the entire area where the two piles were extracted at Sparrows Point. Several months

after the piles were pulled, an engineer of the Bethlehem Steel Company and the writer conducted

measurements on a 9-ft section of 36-in. cast iron

water pipe which was located about 600 ft from the

piles. A maximum current of 40.5 amp with an

average of 13.5 amp was measured over a 20-hr

period. On another pipe of similar dimensions

located approximately 100 ft from the site of pile

I-S, stray-current measurements averaged 3 amp

20-20
with a maximum of 4 amp over the 20-hr period.

The absence of highly locahzed corrosion on the

pilings indicated that they were not acting as con- ductors for the stray currents in the area.

It is also of interest to mention the excellent

condition of a group of identification numbers which was stamped in the steel with }4-in. dies on the 40-yr

pile from the Ouachita River Lock. Although the

mill scale was broken by the dies, the numbers and

the surrounding area were unaffected by corrosion,

as were the roll marks on the pile indicating the

manufacturers identification and patent number.

At all locations, roll marks on the piles where

detected were legible and were in the same condition

as the surrounding surfaces (figs. 4, 5, and 6).

In general the data obtained from the piling

inspections do not show any correlation between

soil properties and the condition of the pile surfaces

in the different soil environments, with the possible

exception of pH. Maximum corrosion was observed on the pilings exposed to extremely acid soils in the

water table zone at Lumber River {pTl 2.3) and

Sparrows Point (^H 3.7), and below the water table zone at Sardis Dam (pH 2.9). The soils in the

piling investigation cover as wide a range of properties as the soils included in the early NBS field tests. The results of the earlier tests showed that

there is at least a rough correlation between the

corrosion of iron or steel and certain soil properties,

such as resistivity, ^'H and chemical composition.

The major difference between the soils at the

NBS test sites and the soils into which the pilings were driven appears to be the oxygen content. The data from the early soil-corrosion tests and most

corrosion data reported previously on service struc- tures were obtained on specimens or structures located in backfilled soil. The backfilling causes a

drastic disturbance in the oxygen content of the

soil and promotes corrosion of iron and steel by

differential aeration. On the other hand, the

oxygen concentration of undisturbed soils is not

sufficient to cause appreciable corrosion of pilings

that are driven into the ground.

It would seem that the soil types which range

from pervious sands to tight impermeable clays at

different horizons at the same locations, would

differ sufficiently in oxygen content to promote

corrosion by differential aeration. Accelerated cor- rosion on pilings could also be expected to occur due to galvanic effects resulting from the presence

of mill scale and exposed bare metal in adjacent

areas. However, the data from the piling inspections indicate that there is not enough oxygen

available a short distance below the ground line,

and especially below water table zones, to promote

corrosion by differential aeration or other causes. Obviously, regardless of the soil properties, sufficient

circulation of oxygen is essential for corrosion to occur. Evidently some corrosion of steel piles takes place

initially after the piles are driven as indicated by the

removal of miU scale in small areas and localized

pitting at some of the locations. The corrosion is evidently arrested after the limited amount of

21-

oxygen has been depleted by the initial corrosion

process and corrosion ceases thereafter because of the

inability of the soil to replenish the oxygen.

The importance of oxygen as a factor in the cor- rosion process was previously indicated, by the

behavior of steel in the modified Denison corrosion

cell set up under aerated and unaerated conditions

in the laboratory on soil samples from the Bonnet

Carre Spillway (fig. 7). The data obtained from the inspections of steel pihngs indicate that there is not sufficient oxygen

available in xmdisturbed soils to cause appreciable

corrosion on driven pilings regardless of the soil properties. Even wet cinders which were present

in the water table zone adjacent to the floodwalls

excavated at Vicksburg and Memphis had no

corrosive effect on the steel pile surfaces.

Appreciable quantities of soluble salts in the form

of sulfates and other ions were present in the soil to which the pilings from the Memphis FloodwaU

and Berwick Lock were exposed. The internal

drainage at the sites, soil pH, and the presence of

organic matter constituted conditions imder which

sulfate-reducing bacteria would be expected to

thrive. However, no evidence of accelerated cor- rosion by the anaerobic bacteria were detected on

the piles at these sites. In fact, at none of the locations where pilings were examined were sulfides

detected in the corrosion products.

Examination of the data in table 3 and section 4

shows that in general soil type, drainage, soil resistivity, ^H, or chemical composition of soils are

of no importance in determining the corrosion of

steel pilings driven in undisturbed soils. This is contrary to everything published pertaining to the

behavior of iron and steel under disturbed or backfilled soil conditions. Hence, soil corrosion data

published in NBS Circular 579 [1] are not applicable

and should not be used for estimating the behavior

of steel pilings driven in undistiu-bed soils. Likewise,

survey methods, as recommended by Skipp [15]

and others, are of no practical value in predicting

the extent of corrosion of steel pilings underground.

6. Summary

Steel pilings which have been in service in various

underground structures for periods ranging between

7 and 40 yr were inspected by pulling piles at 8

locations and making excavations to expose pile

sections at 11 locations. The conditions at the

sites varied widely, as indicated by the soil types

which ranged from well-drained sands to impervious

clays, soil resistivities which ranged from 300 ohmcm to 50,200 ohm-cm, and soil ^H which ranged

from 2.3 to 8.6. The data indicate that the type and amount of

corrosion observed on the steel pilings driven into

undisturbed natural soil, regardless of the soil characteristics and properties, is not sufficient to significantly affect the strength or useful life of

pflings as load-bearing structures. Moderate corrosion occurred on several piles

exposed to fill soils which were above the water table
level or in the water table zone. At these levels the

pile sections are accessible if the need for protection

should be deemed necessary.

It was observed that soil environments which are severely corrosive to iron and steel buried under

disturbed conditions in excavated trenches were not

corrosive to steel pilings driven in the undisturbed

soil. The difference in corrosion is attributed to the differences in oxygen concentration. The data

indicate that undistm-bed soils are so deficient in

oxygen at levels a few feet below the ground line or below the water table zone, that steel pilings are not appreciably affected by corrosion, regardless of

the soil types or the soil properties. Properties of

soils such as type, drainage, resistivity, pH or chemical composition are of no practical value in determining the corrosiveness of soils toward steel pilings

driven undergromid. This is contrary to everything

previously published pertaining to the behavior of

steel under distiu-bed soil conditions. Hence, it can be concluded that National Bureau of Standards

data previously published on specimens exposed in

disturbed soils do not apply to steel pilings which

are driven in undistm-bed soils.

The author acknowledges the support in this program of the American Iron and Steel Institute,

the U.S. Corps of Engineers, and the Waterways

Experiment Station of the Corps of Engineers.

The author is especially grateful to the following

individuals who rendered assistance by participating

in various phases of the investigation: Harold

Ardahl, Corps of Engineers, Lower Mississippi

Valley Division; Walter B. Farrar, Corps of Engineers, Office of Chief Engineer; F. E. Fahy, Chairman

of the Piling Subcommittee of the A.I. S.I. Committee on Building Research and Technology;

C. P. Larrabee, United States Steel Company;

T. D. Dismuke, Bethlehem Steel Company; and

W. D. Tryon, Williams-McWilliams Industries, Inc.

7. References |

[1] Melvin RomanofiF, Underground corrosion, National ] Bureau of Standards Circular 579. U.S. Government \ Printing Office, Washington 25, D.C., (1957). j [2] Paul Anderson, Substructure Analysis and Design, p. , 139, 2d Ed., The Ronald Press, New York, New York j (1956). I [3] G. A. Hool and W. S. Kinne, Foundations, Abutments 1 and Footings, p. 204, 2d Ed., McGraw-Hill Book ! Company, Inc., New York, N.Y., (1943). ! [4] J. G. Mason and A. L. Ogle, Steel pile foundations in I Nebraska, Civil Eng. 3, No. 9, 533 (1932). ; [5] Louis Beaudry, Quay wall design and construction. Eng. i J. (Canada) 14, 394 (1931). >

[6] Steel shells in service 39 years still sound and serviceable, i Eng. News-Record 100, No. 15, 590 (Apr. 12, 1928). 1 [7] Life of steel sheet piling, Iron Age 129, No. 23, 1247

(June 9, 1932).

[8] B. M. Gallaway, A report on some factors affecting the j life of steel pilings in the Texas Gulf Coast area, | Texas Transportation Institute, College Station, i Texas (Oct. 1955). ! [9] G. G. Greulich, Extracted steel H -piles found in good | condition, Eng. News-Record, 145, No. 8, 41 (Aug. ] 24, 1950). \ [10] C. V. Brouillette and A. E. Hanna, Corrosion survey of

steel sheet piling. Tech. Report 097, U.S. Naval Civil ! Engineering Laboratory, Port Hueneme, California ' (Dec. 27, 1960).

j [11] M. N. Lipp, Some data on beach protection works. Civil i Eng. 6, No. 5, 291 (1936). j [12] C. W. Ross, Deterioration of steel sheet pile groins at I Palm Beach, Fla., Corrosion 5, No. 10, 339 (1949).

j [13] A. C. Rayner and C. W. Ross, Durability of steel sheet • pilings in shore structures, Tech. Memo. No. 12, ] Beach Erosion Board, Corps of Engineers, U.S. Army | (Feb. 1952).

\ [14] Laurits Bjerrum, Norwegian experience with steel pile I foundations to rock, J. Boston Soc. Civil Eng. 44, I No. 3, 155 (1957). | [15] B. O. Skipp, Corrosion and site investigation. Corrosion

Technol. 8, No. 9, 269 (Sept. 1961). , [16] W. J. Schwerdtfeger, Laboratory measurement of the j corrosion of ferrous metals in soils, J. Research NBS j 50, 329 (1953). j

Washington, D.C.

22-22

U.S. GOVERNUENT PRINTING 0rFICE:l?62
CORROSION EVALUATION OF STEEL TEST PILES

EXPOSED TO PERMAFROST SOILS

Melvin Romanoff

Institute for Materials Research

National Bureau of Standards

Washington, D. C.

Reprinted from PROCEEDINGS 25th CONFERENCE, National Association of Corrosion Engineers, March, 1969, pp. 6-13 Copyright 1970 by the National Association of Corrosion Engineers
CORROSION EVALUATION OF STEEL TEST PILES

EXPOSED TO PERMAFROST SOILS

Melvin Romanoff

Institute for Materials Research

National Bureau of Standards

Washington, D. C.

Introduction

The performance of steel pilings in soils is being

investigated by the National Bureau of Standards (NBS)

with the cooperation of the American Iron and Steel

Institute and the U. S. Army Office of Chief of Engineers

(OCE).

The purpose of the investigation was to obtain more

accurate estimates of the useful life of steel pilings by

determining the extent of corrosion on pilings after many

years of service in different underground environments. The

results of the first stage of the investigation have been

published.'

The U. S. Army Cold Regions Research and Engineering Laboratory (CRREL) installed test piles at their Alaska

Field Station (AFS) between 1952 and 1957. The purpose

of the investigation was to determine the time for failure of

the soil-to-pipe bond resulting from load-settlement tests conducted by CRREL; and, also, to investigate the corrosion of steel pilings in permanently frozen soils. This paper

is concerned with only the corrosion aspect. As part of the joint investigation being conducted by

NBS and OCE on the corrosion of steel piles in under- ground environments, CRREL arranged for representatives of NBS and the U. S. Army Engineers Division, Lower

Mississippi Valley, Corps of Engineers, to extract 9 steel test piles from the AFS sites. The pile specimens ranged in age from 6 to 1 1 years. Personnel and equipment to remove

the piles and assist in the inspection were provided by the AFS.

Geologic and Climatic Conditions at AFS

The CRREL Alaska Field Station is located about 2

1/2 miles (4.0 km) northeast of Fairbanks, Alaska. The mean annual temperature is about +26 F (-3 C) with a mean

normal high temperature of 70 F (21 C) and yearly normal

low temperature of -20 F (-29 C). The freezing season

usually begins in early October and the thawing season about the middle of April. The annual rain is about 1 1 in (0.3 m). The annual snowfall is about 60 in (L5 m).

The terrain is gently sloping. Geologically, the area is located on the colluvial slopes above the valley fill. The soil

at the AFS is mainly silt with some peat, fine sand and

clayey silt of low plasticity. Under natural surface conditions the maximum depth

of seasonal thaw varies from 2 to 6 ft (0.6 to 1.8 m). The

permafrost layer in the area ranges from 100 to 150 ft (30

to 45 m) in thickness. Permafrost temperatures in the upper 30 ft (9.1 m) may vary from 29 F to 31.5 F (-2 C to OC)

depending on surface cover. Test piles have been installed in 3 sites at AFS which

are designated as Sites A, B and C.

Test Sites

Test Sites A and B were constructed between April and

August 1952. Each site consists of an area approximately 100 by 200 ft (30 x 61 m). Site A was cleared of trees and

brush and the surface organic layer left essentially un- disturbed during and after the installation of the test piles. Site B was cleared and stripped of the surface organic

material about 2 years prior to selection of the area for the

test site. The elevations at the ground surface and at the top of the permafrost layer at Site A are about 476 ft (145.1

m) and 472 ft (143.8 m), respectively. The active layer, which freezes and thaws annually, is between the ground

hne and the top of permanently frozen soil. At Site B, the elevations at the ground surface and the top of the permafrost layer are about 474 ft (144.5 m) and 468 ft (142.6 m), respectively. Typical soil borings at Sites A and B are given in Table 1

Test Site C consists of an area approximately 200 ft (61 m) square. The site was initially undisturbed and

clearing of trees and brush was accomplished prior to

installing the test piles. The surface layer of organic

material was preserved during the pile installation period

and during the subsequent years. The elevations at the ground surface and the top of the permafrost layer at this

site are about 497 ft (151.4 m) and 493 ft (150.3 m),

respectively. A typical soil boring at Site C is given in Table

2.

23-6
TABLE 1 - Typical Soil Borings at Test Sites A and B

Group

Symbols^" Soil DeKription

Depth

Ground

ft

Below

Une<'>m

ML

Gray-brown silt with organic matter 0 to S 0 to 1.5

ML

Gray silt with high organic content S to 14 1.5 to 4.3

Pt Brown organic layer . . . .14.0 to 14.5 4.3 to 4.4

ML

Gray silt with little organic matter US to 20 4.4 to 6.1

ML,CL Clayey silt 20 to 21 6.1 to 6.4

Classified according to: Unified Soil Classification System for Roads,

Airfields, Embankments and Foundations. Military Standard MIL-STD 6I9A (March 20, 1962), Department of Defense, Washington, D. C. 'cround line elevations at Sites A and B are about 476 and 474 ft (I4S and 144 m) mean sea level, respectively.

Installation of Test Specimens

A total of 32 test piles was installed to depths of 13 to 23 ft (4.0 to 7.0 m) below the ground surface, in each of

Sites A and B between April and August 1952. During April

1957, 93 test piles were installed from 8 to 22 ft (2.4 to 6.7 m) below ground surface in Site C. The steel piles^'^ consisted of pipe and H-piles. The H-piles consisted of the following sections; 8B15 (light beam), 6WF25 (wide flange)

and 10BP42. Timber and pre-cast reinforced concrete-piles

also were included among test piles at sites for load- settlement and other tests conducted by CRREL.

The piles were installed by different methods, as follows: (1) in holes formed by steam thawing;

(2) in holes formed by dry augering; and

(3) driving with a pile hammer powered by compressed

air. In the steam-thawed holes, the piles were installed directly

in the silt-water slurry resulting from the steaming process and little or no additional backfill was required. In the dry-augered holes, the pile backfills consisted of silt-water

slurry or clay -water slurry, manually or machine mixed.

The slurry was rodded and vibrated during placement. Soil for the silt-water slurry consisted of the cuttings removed

from the particular pile hole during the augering operation.

Soil for the clay-water slurry was procured from the coal mining area near Healy, Alaska. The water used for slurry was obtained from a local well located near the Chena

River, Fairbanks. During subsequent years after installation, load-settle- ment tests were performed on some piles to determine

possible failures in the bond between the soil and pile.

The steel piles conform to the requirements of ASTM Standard

Specifications for Steel for Bridges and Buildings, ASTM Designation A7.

TABLE 2 - Typical Soil Boring at Site C

Group

Symbols*') Soil Deictiption

Depth Below Ground Line* '

ft m

Pi 0 to 0.5 Oto 0.15 OL Organic silt 0 5 to 4.0 0.15 to 1.2 ML Silt with high organic content .4.0 to 4.5 1.2 to 1.4

Pt 4 5 to 4.8 1.4 to 1.5 ML Gray silt 4 8 to 7.5 1.5 to 2.3 OL Organic silt 2.3 to 2.4

ML, OL, Pt Layers of silt with varying amounts of organic matter .8 0 to 11 2.4 to 3.3 ML Gray silt with clayey silt . . . II to 21 3.3 to 6.4 OH Organic clay 21 to 22 6.4 to 6.7

Classified according lo: Unified Soil Classification System for Rosds,

Airfields. Embankments and Foundations. Military Standard MIL-STD

6 1 9A (March 20. 1 962), Department of Defense, Washington, D. C. Ground line elevation about 497 ft (151 m) mean sea level.

Piles Removed for Corrosion Studies

Nine steel test piles were extracted during July 1963.

Five piles were removed from Site A, one from Site B and

three from Site C. The piles were extracted from the sites by a thawing operation. A steam point, 90 psi (63

kgf/mm^) steam pressure was advanced adjacent to and down to the depth of the pile until the pile heaved up. The

pile was then lifted out of the thawed soil with a crane (Figure 1). After removal of the piles from the 3 sites, they were

assembled in one area where they were steam cleaned

(Figure 2). The piles were then examined for corrosion. After the examination was completed, 6-ft (1.8 m) sections were cut from pile specimens A17, A25, A32, B7D, C9 andC81 and

shipped to the Corrosion Laboratory at the National Bureau of Standards for further study. The samples cut from the pile specimens were from zones exposed about 6

in (0.2 m) above ground surface to below the top of the permafrost, that is, in the active layer which thaws and

freezes annually.

Soil and slurry samples collected at the time of pulling each test pile also were forwarded to the NBS Corrosion

Laboratory. Soil resistivities and pH of the samples are given in Table 3. The types of piles, methods of installation, exposure

times, condition of the piles and other pertinent information follow:

Site A

Pile No. A 17 Date pile driven: April 21, 1952

Date pile pulled: July 22, 1963 Age of piling: 1 1 yeais Type of piling: Steel pipe pile, 8-in (0.20 m) diameter. 0.272 in (6.9 mm) wall thickness, 25 lb/ft (37 kg/m).

24-7
Method of installation: A cone-shaped steel plate was welded over one end of the pipe and the pile installed with closed end down.

Pile installed in 12 in (0.3 m) diameter dry-augered hole and

backfilled with silt-water slurry. The slurry was mixed manually

using soil cuttings removed from the hole.

Exposure Data ft m

Overall pile length 23.8 7.2 Total embedment below ground surface . . 21.0 6.4 Embedment in permafrost 16.4 5.0 Above ground line 2.8 0.8

Condition of Pile:

Above ground - 2.8 ft (0.8 mj: light film of rust, no metal attack or

pitting visible. Active Region - Ground line to 4.6 ft (1.4 m) below: Slight metal

attack and pitting in localized areas. No pits measured greater than 20 mils (0.5 mm) in depth, except 2 pits at 4 ft (1.2 m)

depth which measured 22 and 28 mils (0.6 and 0.7 mm). About

60 percent mill scale intact. Permafrost Region - 4.6 ft (1.4 m) to bottom ofpile: Mill scale 100

percent intact. No metal attack or pitting. Welds on the pipe at

3 ft (0.9 m) from the bottom and at the bottom of the pile were unaffected by corrosion. Photographs of pile A17 are shown in Figures 3 and 4.

Pile No. A23

Date pile driven: July 1, 1952 Date pile pulled: July 23, 1963 Age of piling: 1 1 years Type of piling: Steel pipe, 8 in (0.20 m) diameter, 0.272 in (6.9 mm) wall thickness, 25 lb/ft (37 kg/m).

Method of installation: Installed in 12 in (0.30 m) diameter steam thawed hole formed by advancing a steam point to full specific^

pile depth and continuing the steaming until a hole of adequate

FIGURE 1 — Extraction of steel pile in permafrost at Fairbanks, Alaska. Soil was thawed by advaitcing a steam jet adjacent to and down to the depth of the pile until the pile heaved up.

FIGURE 2 - Test piles prepared for inqiection after cleaning. Left to ri^t: Specimen A25. A17,

A23, A31, A32. B7D and C9.

25-8
TABLE 3 — Data on Soil Samples Removed from Specimens During Extraction

Site

Test PUe Location of Soil Sample

Soil Group

Symbol^ Soa Type pH

Resistivity at60F

ohm-cm

A A17 17 ft (5.2 m) below ground

surface ML Brown, silty clay

6.1 3,000

A A23 Surface ML Dark-brown,

silty clay with

organic matter

7.0 4,200

3 ft (0.9 m) below ground

surface ML Gray silt 6.8 3,850

Slurry ML Gray silt 6.9 1,350 A A25 Surface ML Brown, silty clay 5.4 5,210

3 ft (0.9 m) below ground

surface CL Brown, silty clay 6.1 4,500

Slurry CL Tan, silty clay 6.9 2,410 A A31 11 ft (3.3 m) below ground

surface ML Brown, silty clay with organic matter

6.7 1,420

A A32 20 ft (6. 1 m) below ground

surface ML Gray silt 6.1 11,500

B B7D 15 ft (4.6 m) below ground

surface ML, Ft Gray, silty clay with high peat content

5.6 7,700

C C9 Surface OL Black organic

silt

5.8 3,510

Slurry ML Tan, silty clay 6.5 1,440

C C61 3 ft (0.9 m) below ground

surface OL Black organic

silt

5.6 4,700

C C81 1 ft (0.3 m) below ground

surface OL Black organic

silt

7.6 2,540

5 ft (1.5 m) below ground

surface ML Silt with high

organic content

7.2 3,850

Slurry ML Gray silt 6.9 1,970

Slurry CL Gray clay 6.7 1,890

^Classified according to: Unified Soil Classification System for Roads, Airfields, Embankments and

Foundations. Military Standard MIL-STD 619A (March 20, 1962), Department of Defense, Washington,

D. C.

diameter was formed. A cone-shaped steel plate was welded

over one end of the pipe and the pile installed closed end down. The pile was installed in the existing silt-water slurry in the pipe

hole resulting from the steaming process. Additional slurry backfill was added near the top of the pile hole as needed.

Exposure Data ft m

Overall pile length 24.6 7.5 Total embedment below ground surface . . 21.0 6.4 Embedment in permafrost 17.0 5.2 Above ground line 3.6 1.1

Condition of Pile:

Above ground - 3.6 ft (J. J mj: Thin uniform film of rust, no

measurable pits.- Active region - ground line to 4.0 ft fl.2 m) below: Mill scale about 70 percent intact. Slight metal attack and pitting in isolated

areas. No measurable pits beyond the thickness of mill scale (maximum scale thickness 20 mils).

Permafrost region - 4.0 ft (1.2 m) to bottom of pile: Mill scale 100

percent intact. No visible metal attack or pitting.

26-9
FIGURE 3 — Pips pile specimen No. A17 prepared for inspection in the field after steam cleaning.

FIGURE 4 — Conditions of sections of pipe pile A17

exposed above the ground line and in the active (thaw)

region. Final inspections of these sections were made in the

laboratory.

Pile No. A25 Date pile driven: April 22, 1952

Date pile pulled: July 23, 1963 Age ofpile: 11 years Type of pUing: Light beam, 8B15, 8 in (0.20 m) x 4 in (0.10 m), 15

lb/ft (22 kg/m).

Method of installation: Installed in 12 in (0.30 m) diameter hole dry-augered and backfilled with silt-water shiny, mixed

manually using soil cuttings removed from the hole.

Exposure Data ft Overall pile length 23.4 Total embedment below ground surface . . 20.8 Embedment in permafrost 16.0 Above ground line 2.6

m

7.1 6.3

4.9

0.8

Condition of Pile:

Above ground - 2.6 ft (0.8 mj: Thin uniform film of rust over

entire surface. No pitting. Active region - 4.8 ft (1.5 mj below surface: Mill scale about 75

percent intact. Metal attack with some pits up to 18 mils (0.4 mm) in the area between 3 to 5 ft (0.9 to 1.5 m) below the ground line. Other pits measured less than 10 mils (0.2 mm) in depth. Permafrost region - 4.8 ft (1.5 mj to bottom of pile: Mill scale 100

percent intact. No evidence of pitting or metal attack.

Photographs of pile specimen A25 are shown in Figure 5

Pile No. A31

Date pile driven: August 3, 1952

Date pile pulled: July 23, 1963 Age ofpile: 1 1 years Type of piling: Light beam, 8B15, 8 in (0.20 m) x 4 in (0.10 m), 15

lb/ft (22 kg/m).

Method of installation: Installed in 12 in (0.3 m) diameter steam thawed hole formed by advancing a steam point to full specified

pile depth and continuing the steaming until adequate diameter

hole was formed. The pile was installed in the existing silt-water slurry in the pile hole resulting from the steaming process. Additional silt-water slurry backfiU added near the top of the

pile hole as needed.

Exposure Data ft m

OveraU pile length 23.5 7.2 Total embedment below ground surface . . 20.4 6.2 Embedment in permafrost 16.0 4.9 Above ground line 3.1 0.9

27-10
Above ground - 3.1 ft (0.9 m): Surface completely covered with

thin film of rust. Numerous pits not exceeding 20 mils (0.5 mm) in depth. Active region - 4.4 ft (1.3 mj below ground: MiQ scale about 50

percent intact. Slight metal attack in areas where mill scale was

removed. No measurable pits greater than 10 mils (0.2 mm) in depth. Permafrost regions - 4.4 ft (1.3 mj to bottom ofpile: This section was unaffected by corrosion. Mill scale 100 percent intact.

Above ground -3.8 ft (1.2 mj: The entire surface was covered with

a thin uniform layer of rust. Isolated shallow pits had a maximum depth of 20 mils (0.5 mm).

There was a weld in the beam at the ground line. Although

the weld was rusted, there were no measurable pits. Active region - 4.4 ft (1.3 mj below ground: Mill scale about 60

percent intact. Metal attack and shallow pits present. Pits were

less than 20 mils (0.5 mm) in depth. Permafrost region - 4.4 ft (1.3 mj to' bottom of pile: Mill scale intact over the entire surface. No evidence of corrosion.

Pile No. A32

Date pile driven: July 3, 1952

Date pile pulled: July 23, 1963 Age ofpile: 11 years Type of piling: Light beam, 8B15, 8 in (0.20 m) x 4 in (0.10 m), 15

lb/ft (22 kg/m). Method of installation: Installed in 12 in (0.3 m) diameter steam thawed hole and backfilled exactly as Pile A31.

Site B

Pile No. B7D

Date pile driven: October 27, 1955 Date pile pulled: July 24, 1963 Age of pile: 8 years jype ofpiling: Steel pile, 8 in (0.20 m) diameter, 0.272 in (6.9 mm)

wall thickness, 25 lb/ft (37 kg/m). Method of installation: Installed by driving with a No. 7 pile hammer powered by compressed air. The bottom of the pipe

pile was open.

Exposure Data ft m

OveraU pUe length 23.9 7.3 Total embedment below ground surface . . 20.1 6.1 Embedment in permafrost 15.7 4.8 Above ground line , 3.8 1.2

Exposure Data ft m

Overall pile length 22.5 6.8 Total embedment below ground surface . . 19.5 5.9 Embedment in permafrost 13.0 4.0 Above ground line 3.0 0.9

28-11
Condition of Pile:

Above ground -3.0 ft (0.9 m): Surface covered with thin uniform

film of rust. There were no measurable pits. Active region - 6.5 ft (2.0 m) below ground: Mill scale about 50

percent intact on the surface. Metal attack and isolated pitting present. Four pits measured between 22 and 27 mils (0.6 and

0.7 mm) in depth. Many pits measured up to 20 mils (0.5 mm)

in depth. Permafrost region - 6.5 ft (2.0 m) to bottom of pile: Mill scale intact over entire surface. Surface of pile unaffected by

corrosion.

SiteC

Pile No. C9

Date pile driven: April 23, 1957 Date pile pulled: July 24, 1963 Age ofpile: 6 years Type of piling: Steel H-pile, 10BP42, 10 in x 10 in (0.25 m x 0.25 m), 42 lb/ft (62 kg/m). Method of installation: Installed in 18 in (0.5 m) diameter hole, augered dry and backfilled with machine mixed silt-water slurry using soil cuttings removed from the hole during augering.

Exposure Data ft m

Overall pile length 13.8 4.2 Total embedment below ground surface . . 12.3 3.7 Embedment in permafrost 7.3 2.2 Above ground line 1.5 0.5

Condition of Pile:

Above ground - 1.5 ft (0.5 m): Mill scale about 25 percent intact over surface. Rust present on the rest of the surface. No

measurable pits visible. Active region - 5.0 ft (1.5 m) below ground: Mill scale about 70

percent intact on the surface. Pit depth, maximum 12 mils (0.3 mm), did not exceed the thickness of the mill scale. Permafrost region - 5.0 ft (1.5 mj to bottom of pile: Surface unaffected by corrosion. Mill scale intact over entire surface. Markings in white paint made on the pile prior to installation were still present and legible.

Pile No. Cei

Date pile driven: April 17, 1957

Date pile pulled: July 24, 1963 Age of pUe: 6 years Type ofpiling: Steel pile, 8 in (0.20 m) diameter, 0.375 in (9.5 mm)

wall thickness, 36 lb/ft (54 kg/m). Method of installation: Installed in 14 in (0.36 m) diameter hole, augered dry and backfilled with machine mixed silt-water slurry using soil cuttings removed from the hole during augering. A

flat steel plate was welded over one end of the pipe and the pile installed closed end down.

Exposure Data ft m

Overall pile length 21.0 6.4 Total embedment below ground surface . . 20.1 6.1 Embedment in permafrost 15.6 4.8 Above ground line 0.9 0.3

Condition of Pile:

Above ground - 0.9 ft (0.3 m): Mill scale present over 25 percent of

surface. No measurable pit depths present. Active region - 4.5 ft (0.3 mj below ground: Mill scale, which was

broken in localized area was intact over 75 percent of the

surface. No measurable pit depths greater than 10 mils (0.2 mm).

Permafrost region - 4.5 ft (1.3 mj to bottom of pile: Mill scale about 90 percent intact over surface. The steel was bright in the

areas where the mill scale was broken. No evidence of metal

attack or pitting was visible.

Pile No. CSl

Date pile driven: April 26, 1957

Date pile pulled: July 24, 1963 Age of pile: 6 years Type ofpUing: Steel H-pUe, 6WF25, 6 x 6 in (0.15 m x 0.15 m), 25

lb/ft (37 kg/m).

Method of installation: Installed in 14 in (0.36 m) diameter hole, augered dry. Backfilled to 5.5 ft (1.7 m) from ground surface with machine mixed clay-water slurry. Considerable vibrating and rodding was required for placement of the clay-water

slurry. Upper 5.5 ft (1.7 m) of pile backfill consisted of

silt-water slurry.

Exposure Data ft m

Overall pile length 16.9 5.1 Total embedment below ground surface . . 15.5 4.7 Embedment in permafrost 11.5 3.5 Above ground line 1.4 0.4

Condition of Pile:

Above ground - 1.4 ft (0.4 mj: Uniform rust over 50 percent of the

surface. MiU scale intact over the remaining half of the surface. No measurable pits present.

FIGURE 6 - Condition of flange (left) and ¥veb (right) sections from H-pile specimen C81 exposed in the thaw and

permafrost regions.

29-12
Active region - 4.0 ft (1.2 m) below ground: With the exception of

a few pits about 2 ft (0.6 m) below the ground line, which

measured up to 18 mils (0.5 mm) in depth, there were no

measurable pits greater than 10 mils (0.2 mm) in depth. Mill

scale intact over 90 percent of the surface. Permafrost region - 4.0 ft (1.2 mj to bottom of pile: Pile surface unaffected by corrosion. Mill scale intact over entire surface.

Figure 6 shows web and flange views of sections of H-pUe C81 exposed in the thaw and permafrost regions.

Summary

Nine steel test piles exposed in 3 soil sites at the Alaska

Field Station of the U. S. Army Regions Research and

Engineering Laboratory at Fairbanks, Alaska, were

extracted to investigate the extent of corrosion on the piles. Each of the pipe and H-pile specimens was exposed

underground for 6, 8 or 11 years in an active horizon in which the soil thaws and freezes annually to a depth of approximately 5 ft (1.5 m) and in permanently frozen soil beneath the active layer. Test piles were installed to depths of 21 ft (6.4 m)

below ground surface by several different methods in soils which varied in texture from silt to clay. The pH of the

soils ranged from 5.4 to 7.6. The soil resistivities ranged

from 1 ,350 to 1 1 ,500 ohm-cm (Table 3). Inspections showed that the steel piles were unaffected by corrosion in the permafrost regions. The original mill

scale on the test piles was intact over the entire surface in this region.

Although mill scale was removed from as much as 50

percent and as little as 10 percent of test pile surfaces in the

active or thaw regions, the extent of corrosion as indicated by metal attack and pitting was insignificant. Except for a few maximum pit depths which ranged up to 28 mils deep

(0.7 mm) on two pile specimens (A 17 and B7D), pit depths on test piles in the active region did not exceed 20 mils (0.5 mm). This is about the thickness of the original mill scale on the steel surfaces. There was no evidence of significant corrosion on the

test piles at the ground line or at the boundary between the thaw and permafrost regions. Data from these inspections on the performance of steel pilings in permafrost soils are in agreement with those previously published on steel pilings which have been exposed up to 40 years in various underground structures under a wide variety of soil conditions.' In the earlier investigation, it was observed in general, that no appreciable corrosion of steel pilings occurred in undisturbed soils below the water table regardless of the soil types or soil properties encountered. Above the water table and in fill soils, corrosion was found

to be variable, but not serious.

Acknowledgments

The author is especially grateful to E. Harold Ardahl, U. S. Army Corps of Engineers, Lower Mississippi Valley

Division, who participated in various phases of the investi- gation. Acknowledgment is made also to the following

cooperators in the program: U. S. Army Office of Chief

Engineers; U. S. Army Cold Regions Research and Engineering Laboratory (CRREL), Hanover, N. J.; CRREL

Alaska Field Station, Fairbanks, Alaska; Piling Subcommittee of the Committee on Building Research and Technology, American Iron and Steel Institute.

References

1. Melvin Romanoff. Corrosion of Steel Pilings in Soils. / of Res. NBS. 66C, No. 3, 223 (1962) July-September; also NBS

Monograph 58, U. S. Government Printing Office, Washington,

D. C.

30-13

PERFORMANCE OF STEEL PILINGS IN SOILS

Melvin Romanoff

Institute for Materials Research

National Bureau of Standards

Washington, D. C.

Reprinted from PROCEEDINGS 2Sth CONFERENCE, National Association of Corrosion Engineers, March, 1969, pp. 14-22 Copyright 1970 by the National Association of Corrosion Engineers
PERFORMANCE OF STEEL PILINGS IN SOILS

Melvin Romanoff

Institute for Materials Research

National Bureau of Standards

Washington, D. C.

Introduction

The magnitude of corrosion that occurs on steel piling

exposed underground is being investigated at the National Bureau of Standards (NBS) with the cooperation of the U.

S. Corps of Engineers and the American Iron and Steel

Institute. The results of the first phase of the investigation were

published in NBS Monograph 58.' Since then, additional data have been obtained from inspections of steel piles after exposure from 6 to 50 years in a wider variety of soil environments in different geographic locations. This paper

gives a summary of the results of the inspections made since publication of Monograph 58. It is intended to publish more detaOed information on the inspections in the near

future to supplement the data in Monograph 58.

Background on Investigation

Data obtained by the National Bureau of Standards on

the corrosion performance of steel piles driven into the ground in a wide variety of soil environments show that the strength and useful life of steel piles are not significantly affected by corrosion.^ These findings are in sharp contrast

to those of earlier corrosion studies in which iron and steel specimens, such as pipe; that are buried under "disturbed"

soil conditions exhibit varying amounts of corrosion.^

Previous studies of the corrosivity of soils toward

metals have been restricted to the behavior of specimens in "disturbed" soils, that is, in trenches or excavations which

were dug and backfilled after installation. These studies^ revealed that the corrosion of ferrous metals varied from

negligible to severe in different soil environments. In such

instances, the major cause of corrosion was attributed to a nonuniform distribution of oxygen and moisture along the

surfaces of the buried metallic structures, which resulted in the formation of oxygen-concentration cells that initiated an electrochemical corrosion process. The earlier investigations conducted in "disturbed"

soils also revealed at least a rough correlation between

corrosion and soil properties, such as pH, resistivity and

chemical composition. The investigation on steel piles in soils was initiated to determine whether these soil properties also affected the corrosion behavior of steel piling. Steel piles are frequently driven in soils to resist lateral pressures from earth and water, or to transmit loads to lower levels. To permit examination of entire lengths of piling, some

of which had been exposed from 32 to 40 years, H-piiing used as load-bearing foundations and sheet piling used as structural members of dams, floodwalls and bulkheads were

extracted from eight locations (Table 1). At seven floodwall

TABLE 1 - Steel Piles Extracted from Structures in Prior Inspections

Length of Piling Age of Exposed Below

Piling Type of Ground Line

Structure Location yr PUing ft m

Bonnet Carre Spillway New Orleans, La. 17 H 122 37.2 Test piling Sparrows Point, Md. 18 H 135 41.4 Corps of Engineers Lock and Dam No. 8 . .Ouachita River, Ark. 40 Sheet 15 4.6 Grenada Dam Spillway Grenada, Miss. 12 Sheet 14 4.3

Sardis Dam Outlet Sardis, Miss. 20 Sheet 3.5 1.1 Simpson-Long Bridge, retaining wall . .New Orleans, La. 32 Sheet 33 10.1 Wilmington Marine Terminal, pile jetty . . .Wilmington, Del. 23 Sheet 100 30.5 Lumber River Bridge, Cofferdam . . . .Boardman, N. C. 37 Sheet 17.5 5.3

31-14
and dam installations where existing structures could not be

disturbed, test holes were excavated adjacent to the sheet

steel pilings, to expose about an 8-ft (2.4 m) width of

piling, for inspection of piling in service in various environments (Table 2). Small pile sections and samples of

the soils collected at different levels during the excavations were forwarded to the laboratory for further study.

The inspections listed in Tables 1 and 2 provided

information on the behavior of steel piling over a wide

range of conditions. For example, backfill material varied in content from riprap, cinders and slag to combinations of

sand, silt, loam and clay. Undisturbed natural soils varied from well-drained sands to impervious clays. Soil resis- tivities ranged from 300 ohm-cm (indicating the presence of

large quantities of soluble salts, normally corrosive under

"disturbed" soil conditions) to over 50,000 ohm-cm

(indicating the absence of soluble salts). The pH of the soils ranged from 2.3 to 8.6. Results of the inspections' disclosed that limited corrosion in the form of highly localized pitting occurred on a few occasions below the water table zone. Laboratory measurements revealed only small or negligible reductions

in wall thickness of the pile specimens. The pitting type of

corrosion is, of course, of major importance in pipelines or other metal structures designed to carry fluids. But, in piling structures, the depth of scattered pitting is not

particularly significant; a uniform reduction in thickness from corrosion of a considerable area of structural surface

is much more serious. Sections of piling exposed to fill soil alone or in the

water-table zone appeared to be the most vulnerable to corrosion. However, only localized pitting was generally

found and these sections were readily accessible for protection, if necessary. The survey showed that soil environments which are normally corrosive toward steel specimens buried in "disturbed" soils are not corrosive to steel piling driven into "undisturbed" soils. The difference in corrosion was

attributed to differences in oxygen concentration. Apparently, "undisturbed" soils are so deficient in oxygen

a few feet below the ground line or below the water-table zone that steel piling is not appreciably affected by

conosion, regardless of soil properties.

It was, therefore, concluded that information on the type, drainage, resistivity, pH, or chemical composition of

soils is of no practical value in determining the corrosive- ness of soils toward steel piling driven into the ground.

Hence, such data should not be used to estimate the corrosion of piling installed in this manner. New Inspections Provide More Data

Since publication of NBS Monograph 58,' additional data have been obtained from inspections of steel piles exposed underground in a wide variety of soil environ- ments. The inspections were conducted by the same

procedures as described elsewhere. At 18 locations the piles were pulled from the soil for inspection. Data pertaining to 8 of these piles are given in Table 3. Nine piles were pulled from permanently frozen

TABLE 2 - Steel Sheet Piles Exposed in Excavated Test Holes

in Prior Inspections'

Length of Piling Age of Exposed Below

Piling Ground Line

Structure Location yr ft m

Memphis Kloodwall .Memphis. Tenn. 7 9.0 2.7 Vicksburg Kloodwall Virk chi 1 ro M ice 7 8.5 2.6 Saidis Dam Spillway . .Saidis. Miss. 20 5.0 15

Grenada Dam Spillway .Grenada, Miss. 1

5.5 1.7 Berwick Lock . . Berwick, La. 1

5.0 1.5 Algiers Lock . . . New Orleans, La. 12 2.5 0.8 Enid Dam .... .Enid, Miss. 12 5.5 1,7

soils, the data for which are presented in another paper.'' Results of an inspection of a test pile extracted by the Philadelphia Electric Company, in which the writer partici- pated, has been previously published. At 17 locations, where it was not possible to pull the

piles without disturbance to the existing structures, test holes were excavated adjacent to the sheet steel piles to expose a width of piling at each location to a depth below

the ground surface which was usually determined by the water table. The soil and corrosion products were removed

from the exposed pilings by wire brushing and scraping and

the condition of the pile surfaces was determined by visual examination and pit depth measurements. A portion of the pile web, approximately 1 ft by 2 ft (0.3 m X 0.6 m), was cut from one or more areas of the exposed pile at each location. During excavation of the test holes, soil samples were collected at different depths. The

pile specimens and soil samples were shipped to the laboratory for further examination. Data pertaining to the soil type, resistivity and pH are given with the inspection results for each location in Tables 4 and 5

Results of the inspections made on bare steel pilings in 13 excavated test holes are given in Table 4, and the results of inspections which were made on steel piles coated with a

coal-tar enamel in 4 test holes are given in Table 5.

Results of Inspections

Tables 3, 4 and 5 show wide variations in the

characteristics and properties of the soils at the locations where the steel piles were exposed. The soil types ranged

from porous sands to silts and impervious clays and

combinations of these types. The soil resistivities ranged

from 78 to 45,000 ohm-cm and the pH from 4.1 to 8.8. At many locations the natural "undisturbed" soils were

covered by an overlay of fill material which consisted of combinations of materials, such as sand, silt, clay, gravel, cinders, oyster shells and various riprap and rubble. At most sites the piles were subjected to different soil types in the different horizons which varied in resistivity and pH. Such differences in soil properties at the same

location can be expected to promote galvanic-type corrosion by differential aeration or the formation of oxygen

concentration cells.

32-15
A summary of the condition of the steel piles is given

in Tables 3, 4 and 5. Table 3 gives data for 8 piles which

were extracted from different structures after exposures from 21 to 50 years. It is interesting to note the absence of

significant corrosion on the steel piles, especially on the pile sections exposed in the low -resistivity soils. For example, a maximum pit of only 50 mils (1.3 mm) was measured on

the 31 -ft (9.4 m) length of pile exposed for 21 years in the

stoplog dam structure at Freeport, Texas, in silty clay and

clay soils which had a maximum soil resistivity of 350

ohm-cm.

The three 27- to 29-year-old piles pulled from the

Mississippi River Lock and Dams Nos. 5, 5 A and 7 were exposed to depths of 30 to 40 ft (9.1 to 12.2 m) in soils which varied from sands to clays and ranged in pH from 4.7

to 7.7 and in soil resistivity from 1750 to over 40,000

ohm-cm. Water tables at the 3 sites were located from 2 to 6 ft (0.6 to 1 .8 m) below the ground line. Inspection results show that only minor corrosion in the form of shght metal

attack and isolated pitting occurred on the sections of the

piles exposed in and above the water table zone.^'^ The

maximum pit depth measured on the three piles was 55

mils (1.4 mm) and the average reductions in wall thickness of the piles were neghgible. Below the water table zone the

piles were practically unaffected by corrosion, the original

mill scale being almost entirely intact over the steel surfaces. Figure 1 shows the condition of pile sections cut from

areas at the water table zone and near the bottom of the

pile that was pulled from the Mississippi Lock and Dam No.

5. The data from the inspections of the remaining four

piles which were extracted from structures at Olcott, N. Y., Buffalo, N. Y., Erie, Pa. and Fairport, Ohio (Table 3) show

performance similar to that noted for the above piles. The

The water table zone includes 2 ft above and below the mean

water table.

TABLE 3 — Steel Piles Extracted from Structures for Inspection

Length of Piling Soil Characteristic t and Properties (Zooditian of Piling SInictuie and

Location

of

Piling yr Type of

Piling

B«low Ground

Inspected

ft m

Depth Below Ground Line

ft m SoBType'" pH

Soil Reaistrvity ohm-cmMaximum

Pit D«plh'^'

mils mm Remajks

Stoplog Dam

I feepoft, Tex.

21 Sheet 315 96 0« 5 0-2.0 Silty clay (CL) - water table 7.5 150-350 SO 13 Isolated pitting at ground line and

water table.

6 5-24 5 2.0-7 5 Cby (CH) and silty clay (CL). 7.2-7,3 10^160 U Unaffected by corrosion.

24.5-280 7.5-8.5 Clay (CH) and silty clay (CL). 7.3-7,5 78-130 U - Shallow metal attack.

28.0-31.5 8.5-96 Silty clay (CL). U Unaffected by corrosion.

CulofT wall -

Mississippi Rrver Lock and Dam No, 5. MtniKsouCity. Minn

29 Sheet 35 3 108 1-13

13-36

O3-4.0

4.0-11 0

Fine to medium sand (SP) -

water table at 2 ft

Silty sand (SM), fine to medium

sand (SP)

7,2-7.3

4.7-5.4

36.000

1860-3400

10

u

02 i-ew isolated pits and slight metal

attack at water table.

Unaffected by corrosion.

CutofTwall -

Mississippi Rnei

Lock and Dam

No SA. Winona.

Minn.

28 Sheet 40 12.2 0-14

14-20

20-42 42-44

0-4 3

4.3-6 1 6.1-12.8 12.813.4

Sand, fme to medium (SP) -

water table at 6 ft

Silty sand (SC). Sand, fine to medium (SP). Sandy silt mixed with clay (ML).

7.5-7.7

6.8-7.2

4.8-5.6 6.2-7 3

41.000

2.660 14.700

1.880

55

U

u

u

1.4 Some pitting in water table zone. I-ew pit depths measured 28 to SS

mils. Other pits were less than 20 mils. Unaffected by conosion

Unaffected by conosion. Unaffected by conosion

CutofTwall

Mississippi River Lock and Dam

No 7. Diesbaek. Minn

27 Sheet 303 9.2 0-2

2-10 10-22

0-0.6

06-3.0

3 0-6 7

Sand, fine to medium (SP) -

water table at 2 ft Sand. cinder-Uke (SP) Sandy silt (ML).

7.5-7.6

5.4-6.9 6.8-74

44,000

1750-8700 31004000

30

V

10

08

02

Scattered metal attack and few

isobted pits. Unaffected by corrosion. Many small pits not exceeding 10

mils in depth at l&12ftand 19-22 ft

22- 23

23- 30

6.7-7 0

7 0-9.1 Gray gumbo clay (CH). Sandy silt and silty clay (CL). 6.7 - 3400-5000 V

V

UnalTected by corrosion. Unaffected by conosion.

Piei-Lake

Onlajio.

Oltolt. N Y

50 I'Beam 4(3) 12 0-05

0.5-4.0 00 2 02-1.2

Soil sample not available

Soil sample not available

45U

11 Isolated pits at mud line. Slight metal attack, no measurable

pits.

kngineeis Slip - Niagaia Rivei. Buffalo. N Y

36 Sheet 5,5<'> 17 0-6

6-8 5

0-18

1 8-2.6

Silty sand (SC)

Silty sand (SC) with himps of

silty clay (CL) - water ubie

at 8 5 ft

7.7- 7.8

7.8- 8 1

1540-2820

161»1920

U

SC 13

Top of pile exposed 3 ft below ground

line. No measurable pits. Uniform metal attack; one pit, 50

mils in depth; other pits did not exceed mill scale thickness.

Stale Groin

No. 8 - Presquc

Isle. trie. Pa

32 Sheet 3j(s) 10 a3 2 0-10 Sand, fine to medium - water

table at 3 2 ft

7.9 - 23.000 65 1.6 Many pits between 30 and 6S mils in depth near ground line. Kew pits up

to 45 mils at water table. Uniform

rust and metal attack over rest of

surface.

Coast Guajd

Slip - Grand

River, l-aiiport. Ohio

30 Sheet 22 3 6 8 0-5

5-8

0-15

15-24

I'ill soil - silty sand with boulders and gnvel(SC)

Clay loam (CL) - water table

at 8 ft

1- ine silt with sand and gravel (SC). blue cUy (CH). sUty cliy with giavel (CD

8.0 -

76 -

4,200

3,500

<20

<20

<a5

<0.5

Metal attack over most of wrfacc

with isolated pit depths.

Same as above.

8-22 3 2.4-6.8 7.2-7.7 1 120*000 U Unaffected by corronon. MiO scale almost 100% intact.

Lcltcri in p^renrhcKi are ihr proup >ymtM>lt for crauifyinf luil lypej according lu the Unified Soil Clauification SyUem for koadt, Airrterdt. V mbanhmenti and houndsiioni. Military Standard MIL STI) 619 A (March 20. 1962). Dcpariment of Defense. WaUtinKton. 1> C

U. indicaici that there were no piti uf meauirahic depth.

A ion (3 0 m) length of tb< *«• extracted The top 2 ft (0 6 m) wai eapoaed to (he atmosphere. 4 fi (i 2 m) exposed in water tnd 4 ft { I 2 m) eiposed below the mud line The section

in the atmosphere had uniform metal attack and isolated pits up

to 40 mils ( 10 mm) m depth The section in water was severely corroded, causini perforation of the wall thickness of the pile

Attempts to pull this pile were unsuccessful. An cicivatlon was made down to the water table and the upper 5.5 fl (1.7 n)

^ ^section of the pile was removed by cutlin|. Attempts to pull this pile were unsuccessful. An eicavtllon was made down to the water tabte and the upper 6.7 fl <2.0 m)

section of the pile wss removed by cutting. The upper 3. J f* m) of the pile wis exposed lo the atmosphere.

33-16
/

TABLE U - Bare Sheet Plies Inspected In Excavated Test Holes

Structure

and Location

Age of Piling

Length of Piling

Exposed Below Ground

ft m

Depth Below

Ground Line

Soil Type CD

Soil iesletivlt

ohni-cni ty?ltMaximum

DepthC2)

rolls Floodwall - Harrlsburg, 111.

5 1.5 0-1.5F111 soll-silty clay mixed

i^lth gray silt (CL)

5-10 1.5-3. OS ilty clay (CL)-wate

5 ft.

Piling In concrete cap.

Scattered pits did not exceed the thickness of the mill scale which

was about 90% Intact. Floodwall - Louisville, Ky. rown firm clay and organic

silty clay (CL.OH).

7-11 2.1-3.33 tiff clay (CH) below 11 ft. water table .1-6.4

Top 5-ft of piling encased in concrete. No pits beyond thickness of

nlll scale which was about 80% Intact.

Same as above.

Floodwall - Jef f ersonville

,

Ind.

0-3 0-0.9Fill soil-clay, cinders

and gravel.

3-11.50.9-3. 5Brown firm clay with tan Drganic matter CCH) ; tan fi 3ilty clay (CL)

Piling capped with concrete from 0

to 7 ft.

^Jo pits beyond thickness of mill

scale which was about 70% Intact.

Guldewall, Colorado River

Locks - Matagorda, Tex.

0-1 0-0.3^111, top soll-silty clay

(CL).

1-12 0.3-3.7?ill consisting entirely of 3roken oyster shells.

L2-16 3.7-4.9^atural soil-silty clay

(CL) with considerable linerfater table at 16 ft.

Slight metal attack; depth of pits penetrated slightly beyond mill

scale thickness.

Jniform corrosion with roany pits up

to 70 mils in depth.

Few pits not exceeding the thickness

of mill scale.

Guldewall

,

Brazos River Floodgates - Freeport, Tex.

0- 1 0-0.3>ilty clay (CL) and organic

silt clay (OL)

1- 8 0.3-2.4?ill consisting of clay (CH) nixed with broken shells-

^ater table at 8 ft.

14 2.4-4.33ame as above.

General metal attack with isolated

pits.

yietal attack over most of surface

with scattered pitting. Deepest

pits (90 mils max.) occur about

2 ft from surface.

Slight metal attack and shallow

pitting. Drain outlet, Clinton River

Flood Control

Project - McComb County,

Mich.

ilty clay (CL) with organic

latter and clayey sand (ML)

5-10 1.5-3.0^ tiff clay (CH)-water table elow 10 ft.

yiill scale intact over 90% of surface. Few isolated pits not exceeding mill scale thickness.

Mill scale intact over entire pile

surface. No corrosion. Floodwall - North Little

Rock, Ark..

ill-very fine silty sand (SO with beads of clay (CH) dispersed throughout

4-5 1.2-1.5:iay(CH).

5-12 1.5-3.7/erv fine siltv sand Cr!C)- -^ater table below 12 ft.

180a-i6y0

9800-11,000

1.3

Top 2 ft of pile capped with concrete. Isolated pitting. Mill scale 90% intact.

Isolated pitting; miUL scale 70% intact

5 [Mill scale about 90% intact. Scattared pits not exceeding 20 mils in depth. Seawall - Charleston, S. C Fill-sand (SP) with

Lumps

ilay 750-2500

-15 2.4-4.6 :iay (CH)-water table at

L2 ft.

Scattered pitting most prevalent

between 2 to 4 ft from surface. Many

pits between 40-75 mils. Few pits between 75-95 mils in depth.

Mill scale practically entirely

intact. No corrosion. Diversion Dam, Jemez River - San Ysidro, N.

11-fine to coarse sand

(SP) with gravel-water table

7 ft.

-10 2.4-3. 0kandy silt (ML)

1855-40,000 Limelike crust over entire surface

of steel. Slight metal attack in some areas. No measurable pits.

No corrosion.

Bridge abutment

retaining wall - Lamar, Colo.

clayey silt (ML) with

*ravel and lime concretions.

ilty sand (SM) and gravelly

3and CSP) -water table

tuates seasonly between

2 to 11 ft.

6-9.5 1.8-2.9:;ravelly sand (SP)

Metal attack over most of surface

and scattered pitting.

Shallow metal attack over most of surface. Many pits up to 30 mils

in depth. Three pits between 90 and 110 mils.

No pit beyond thickness of mill

scale which was about 75% intact. Gate structure

Hartford Dike, Hartford , Conn

0-10 0-3.

LO-14 3.0-4.

ill soil.

ill-clayey silt (ML).

L4-16 4.3-4.9Fill-sandy silt (ML) with

:lay (CL) and cinders

L6-20 4.9-6.l[Fill-sand and sandy silt (SP) uch cinders. Water

table-varies with river stage

jp to top of pile

220

Piling capped with concrete.

Shallow metal attack. Few pits up

to 40 mils in depth.

Scattered pitting up to 170 mils over

15% of surface.

Scattered deep pits up to 220 mils

over 10% of surface.

Seawall jettySnake River -

iNome, Alaska

0-5 0-1.5Fill

silt :inde

5 ft.

lay silt (ML) , sandy

(ML), sand (SP) and rs-water table below

Shallow isolated pits less than 20 mils over about 30% of surface. Many pits between 22 and 80 mils in depth

FloodwallOraaha, Neb

L5-18 4.6-5.5:1,aye

clay

20 ft

silt (ML) and silty

(CL)-water table at Many shallow pits did not exceed

the thickness of the mill scale which was 40% intact. Few pits between 20 to 50 mils in depth.

(1) Letters in parentheses are the group symbols for classifying soil types according to the Unified Soil Classification System for Roads, Airfields, Embankments and Foundations, Military

Standard MIL-STD 619 A (March 20, 1962), Department of Defense, Washington, D. C. (2)u, indicates that there were no pits of measurable depth.

34-17
TABLE 5 - Coated Steel Sheet Piles^ ' Inspected in Excavated Test Holes

Structure and

Location

Age of

Piling y

Length of Piling Inapected Below Ground

tt m

Depth Below Ground Line

ft m SoUType'" pH

Sou

Reattivily ohm-cm

Msdmum

Pit Depth'''

mill mm Remarks

Floodwall - 8 15 4 6 012.5 0-3.8 Fill soil - clayey jill (ML)

With cinders, ^Idss, brick, decomposed wood and metallic waste - water table at 12.S ft.

6.8-7 5 850-1470 60 1.5 Mill scale on steel surface was

about 90% intact. Scattered areas of metal attack and pitting. Many

pits between 4O60 mils in depth.

12.5-15 3.8-4.6 Similar to above. 7.3-7.6 780-1440 U _ Unaffected by corrosion.

ChaiTiber wall, Peail River Lock

No. 1 - Peail River, La.

16 20 6 1 0-17

1 7-20

0-5.2

5.2-6.

Sand with ^avel (SP) — water

table fluctuates between 0-17

ft.

Sand with gravel (SP).

5.1-7.2

5.1-6.6

3n(l(¥l-45(Wi

30000-40000

40 1.0 Scattered small pits between 15

to 40 mils in depth.

Unaffected by corrosion.

Floodwall - 24 6 1.8 0-5 0-1.5 Fill - silt and friable clay (ML CL) with organic matter and cinders.5000-9000 - - Top 6 ft of pile capped with

concrete.

5-11 1.5-3.3 Friable clay (CL) - water table

at 9 ft.

5.9-6.1 2800-3870 U - Mill scale practically 100% intact. No corrosion.

11-12 3 3-3.6 Stiff clay (CH). 6.9-7.1 1650-2040 V No corrosion.

Wingwall.

St. Lucie Canal -

Stualt Fla

24 12.5 38 0-5.5 0-1.7 Fill - sand (SP) and sUty sand (SC) with shells and lumps of clay7.8-8.1 10700-19000 72 1.8 Isolated pits up to 72 mib in depth. Mill scale about 80%

intact.

5.5-8.0 1.7-2.4 Silty sand (SC) and sandy clay (CL).

7.4-7.9 1550-3860 10 0.2 Mill scale about 95% intact. Coating peeled in many areas. No

pits greater than 10 mils in depth.

8,0-12.5 2.4-3.8 Silty sand (SC) and clay (CH) -

water table at 12.5 ft

7.2-7.7 480-3600 10 0.2 Same as above.

'steel piles cuaied with coal-tar enamel befure installiition. Letters in parentheses are the group symbols fur classifying soil types according (o the Unified Soil Classification System for Kuads. Airfields, tmbankments and houndations. Military Standard MIL STD 619 A (March 20, 1962). Department of Defense. Washington. D. C

U. indicates that there were no pits of measurable depth.

maximum pit found on all the piles listed in Table 3 was 65

mils (1 .7 mm) in depth.

Figure 2 shows a section of a 50-year-old I-beam that was extracted from a pier in Lake Ontario at Olcott, N. Y. The photograph shows part of the 4-ft (1.2 m) section of

the pile which was exposed below the mud line. No

measurable pits were found in this section, except for the few isolated pits (maximum depth 45 mils) which occurred

at the mud line. The 4-ft (1.2 m) section of the same pile exposed in the water above the mud line was severely corroded. The condition of sections cut from piles which were

pulled from a 36-year-old structure at Buffalo, N. Y. and a 30-year-old structure at Fairport, Ohio, are shown in Figures 3 and 4, respectively. DeMarco" reported the results of an inspection in which the author participated of a test H-pile pulled at the Eddystone Generating Station in Philadelphia, after exposure for 5 1/2 years in a location where acid leachings

from a coal pile caused severe contamination of the subsoil. The 45 -ft (12.7 m) H-pile was exposed in a porous river sand to a depth of 37 ft (11.3 m) below the ground line, which was underlain by silt. The pH of the soils from the ground Une to the bottom of the pile ranged between 4.6 and 6.4; the soil resistivity ranged between 1600 and

17,500 ohm-cm. The water table was at approximately 15

ft (4.6 m) below the ground line.

DeMarco concluded that, generally, the pile was only

mildly corroded with minor pitting in the water table area. The maximum pit measured was 55 mils (1.4 mm), while the average reduction in wall thickness was estimated at less than 10 mils (0.2 mm). From the examination of the test pile removed and other measurements made throughout the

station, it is anticipated that the service life of the

structural piles will not be impaired by corrosion in the

existing soil environments, even in contaminated material below the coal pile. In another paper, ^ the writer reported the results of

inspections to investigate the corrosion of steel pilings in permanently frozen soils. Nine steel test piles exposed in 3

soil sites at the Alaska Field Station of the U. S. Army Cold

Regions Research and Engineering Laboratory at Fairbanks,

Alaska, were extracted to investigate the extent of corrosion on the piles. The pipe and H-pile specimens were exposed underground for 6, 8 or 11 years in an active horizon in which the soil thaws and freezes annually to a depth of approximately 5 ft (1.4 m) and in permanently

frozen soil beneath the active layer. Test piles were installed to depths of 21 ft (6.4 m) below ground surface by several different methods. Inspections show that the steel piles are unaffected by corrosion in the permafrost regions and that there was no evidence of significant corrosion at the ground

line either in the active or thaw region or at the boundary

between the thaw and permafrost regions.

35-18
FIGURE 1 — Sections from the 29-year-old sheet piling pulled from a cut off wall in the Mississippi River Lock and Dam No. 5 near Winona, Minn. Top—Section exposed about 2 to 4 ft below the ground line in the water table zone. Bottom—Section exposed about 33 ft below the ground line.

Results of Other Tests

Tables 4 and 5 give the results of inspections performed on 13 bare steel piles and 4 coated steel piles exposed in excavated test holes after exposures up to 30 years. Here

again it will be noted that there are large differences in the sou types and properties at the different locations and at different horizons at the same location. At all but three locations (Louisville Floodwall, McComb County Drain

Outlet and Omaha Floodwall), where the bare steel piles were examined in excavations, the "undisturbed" natural

soil was overlain by fill material (Table 4). At three locations (Freeport Guidewall, Hartford Dike

and the Nome Seawall), the bare pile specimens inspected were completely embedded in fill material.

FIGURE 2 — Section of steel I-beam pulled from a pier on

Lake Ontario at Olcott, N. Y., after exposure for 50 years. The section was exposed about 2 ft below the mud line artd was practically unaffected by corrosion.

FIGURE 3 — Section of steel sheet-pile pulled from an

engineer's slip on the Niagara River at Buffalo, N. Y., after exposure for 36 years. The section was exposed about 8 ft below the ground line in the water table zone.

The data from the examinations of the bare pile specimens show, with one exception, that corrosion was

limited to shallow metal attack and isolated pitting on

36-19
FIGURE 4 - Sections from the 30-year-old sheet pile extracted from a Coast Guard slip on Grand River at F airport, Ohio. Top—Section exposed between 4 to 7 ft below the ground line in fill soil and in the water table zone, showing slight metal attack over most of the surface. Bottom—Section cut from bottom of pile about 22 ft below

the ground line, unaffected by corrosion.

surfaces of the pile sections that were exposed in fill material, above the water table, or in the water table zone. The corrosion was generally confined in the upper portions of the piles. At 5 locations, the pits on the bare piles did not exceed the thickness of the mill scale on the steel surfaces. Although pits between 70 and 1 10 mils (1.8 and

2.8 mm) in depth were found on five of the piles, the extent of corrosion cannot be considered appreciable with

respect to the useful life of the structures. The isolated or

localized pits resulted in only negligible or small reductions

in wall thickness of the pile specimens.

The exception occurred on the 23-year-old sheet piling

exposed in the Hartford Dike in connection with construc- tion of a gate structure at the South Meadows Power

Station. The structure was embedded entirely in fill soil

37-

FIGURE 5 — Section of steel-sheet pile cut from an underground gate structure of the Hartford Dike at Hartford, Conn., after exposure for 23 years. There were deep pits over

the entire steel structure which was exposed in fill nil, containing a considerable amount of cinders. The water table

at this location fluctuated from the bottom to the top of the

pile with the river stage.

which contained up to 90 percent cinders. Severe metal

attack and deep pitting up to 220 mils (5 .6 mm) in depth

occurred over large areas of the pile surfaces. The deepest

pits were observed below the 14 ft (4.3 m) level. During the period of one year, the 10-ft (3.0 m) length of piling

examined was subjected to a water table at all levels because the water table at this location fluctuates considerably with the river stage. Figure 5 shows the extent of corrosion on a section cut from the piling in the Hartford Dike. A section of bare steel piling removed from the

Jeffersonville Floodwall after exposure for 20 years is shown in Figure 6. The pit depths did not exceed 10 mils

(0.2 mm) on this structure. Figure 7 shows the corrosion on a section of pile cut from the 27-year-old floodwall at North Little Rock, which

occurred in the transition layer between the fill and natural

soils. The maximum depth of pitting was 50 mils (1.3 nun) on this structure.

20
Figure 8 fJiows a section of piling aft "r exposure in fill

soil containing cinders for 30 years in ilie seawall jetty at the mouth of ihe Snake River at Nome, Alaska. The only corrosion observed on the 4 coated piles which were inspected in the excavated holes (Table 5) occuned in the upper sections of the structures exposed in

fill soil and in water table areas. The corrosion was limited

to localized pits and shallow metal attack.

Discussion and Conclusions

The observations reported in this paper are in agree- ment and substantiate the observations and conclusions based on the results of the previous examinations on steel

pile structures which are pubhshed in NBS Monograph 58.' The data show that, in general, steel pilings are not

significantly affected by corrosion in undisturbed natural

soils, regardless of the soU types and soil properties. Only

minor or moderate corrosion in the form of shallow metal

attack or localized pitting occurred on the upper portions of the pile structures which were exposed in fill or in soils above or in the water table zone. The average reduction in wall thickness on any of the piles examined was not of

sufficient significance to impair the useful life of the

structures.

FIGURE 6 - Section cut from a steel dieet pile about 10 ft below the ground in a floodwall at Jeffertonville, Ind., after •xpowra for 20 years.

Corrosion of any consequence which may possibly have

an effect on a longer Ufe of the structure was observed at only one location where the piling was exposed in a fill contaminated with cinders. Even at this site, despite the deep pitting observed, the structure was still serving its useful purpose after exposure in the environment for 23

years.

It will be observed from the data in Tables 3, 4 and 5 that soil environments which can be predicted to be

severely corrosive to iron and steel under disturbed conditions in excavated trenches^ were not corrosive to steel pihngs driven in undisturbed soils. This observation was also made in the previous report' concerned with the earlier pile investigations. The difference in corrosion was attributed to the differences in oxygen concentration. It was indicated

that undisturbed soils are so deficient in oxygen at levels a few feet below the ground line, or in and below the water

table zone, that steel pilings are not appreciably affected by

corrosion, regardless of the soil types or the soil properties.

FIGURE 7 - Steel dieet pile section cut from a floodwall at North Little Rock, Ark., after exposure for 24 years. The

section was exposed between 3 to 5 ft below the ground line

in fill soil underlain by natural clay soil. The depth of pitting did not exceed 50 mHs.

38-21
FIGURE 8 — Underground section of sheet pile cut from a

seawall jetty at the mouth of the Snake River at Nome,

Alaska, after exposure for 30 years. The section was exposed

in fill and cinder soil just above the water table.

This reasoning does not seem to fully explain the presence of only minor or moderate corrosion or the absence of high corrosion rates on the upper portions of

steel piling exposed in low resistivity fill or natural soils near the surface, in or above the water table zones. It is possible that the little corrosion observed on these portions of the piles occurred during the early exposure periods due

to the corrosive environment. In time, a large galvanic corrosion cell is created between the upper portion of the

pile structure, which lies in the fill or above the water table, and the lower portion of the pile structure. It can be

assumed that the oxygen concentration of the soO decreases with depth, especially below the water table. In such a galvanic cell, the upper portion of the pile which is, in general, a much smaller part of the entire pile length will be cathodic to the much larger portion of the

pile driven into the natural soil which is more deficient in oxygen. The resulting galvanic cell, therefore, consists of a small cathode (upper portion of pile) and a huge anode

(lower portion of pile). The area relation between the anode and cathode would, of course, depend on the total length of the pile; the longer the pile, the greater the anode

area. Because of the large differences in area between the cathode and anode, the amount of iron sacrificed by the anode in protecting the relatively small cathode is negligible. To investigate this hypothesis, an installation of test piles was made during September 1966 in Montreal,

Quebec. Steel H-pile specimens were driven about 35 ft (10.7 m) to bedrock through 8 ft (2.4 m) of a sand-silt- cinder fill which is underlain by natural soil layers

consisting of sand, peat, marl, clay, silt and gravel. The soil resistivities at the sites range from 400 to 5000 ohm-cm. It

is expected that the data to be obtained from periodic

inspections will provide valuable information to supplement

the data obtained on the performance of steel piles in soils.

Acknowledgment

The author acknowledges the cooperation and support

in this program of the American Iron and Steel Institute. The author is especially grateful to E. Harold Ardahl, U. S. Army Corps of Engineers, Lower Mississippi Valley

Division, for his participation in the piling inspections.

References

1. Melvin Romanoff. Corrosion of Steel Pilings in Soils. /. of Res. NBS, 66C, No. 3, 223 (1962) July-September; also NBS

Monograph 58, U. S. Government Printing Office, Washington,

D. C. ($0.20).

2. Melvin Romanoff. Underground Corrosion. National Bureau of

Standards Circular 579, U. S. Government Printing Office, Washington, D. C. (1957). A reproduction copy is available from

the Clearinghouse, U. S. Department of (Commerce, Springfield, Virginia 22151. Order as PB-168350 Underground Corrosion

($3.00).

3. Melvin Romanoff. Corrosion Evaluation of Steel Test Piles Exposed to Permafrost Soils. Proceedings, NACE 25th Conference, 1969. National Association of Corrosion Engineers, Houston, Tejias.

4. R. C. DeMarco. Protection of Underground Steel in a Highly

Corrosive Area. Materials Protection, 3, No. 2, 42 (1964)

February.

39-22
JOURNAL OF RESEARCH of the National Bureau of Standards— C. Engineering and Instrumentation

Vol. 75C, No. 2, April-June 1971

Polarization Measurements as Related to Corrosion

of Underground Steel Piling

W. J. Schwerdtfeger

Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234

(April 14, 1971)

Most of this paper is devoted to the author's evaluation of polarization measurements made by the Corps of Engineers (Lower Mississippi Valley Division) on steel pipe specimens exposed to the soil at four dam sites as related to the corrosion of steel piling (underground) observed at the sites. As the polarization measurements were made periodically on weighed specimens for periods as long

as seven years, the Corps' data offered an excellent opportunity for evaluating the accuracy and

practicability of a polarization technique for measuring corrosion rates. Reasonable agreement between calculated and actual corrosion on the specimens made it possible to estimate maximum

anticipated corrosion on the piling after 50 years of exposure. Confidence gained in the value of polarization measurements made on short length pipe specimens

led the author to make measurements on actual piling. Instantaneous corrosion rates were measured

on two driven pipe piles, 72 ft (22 m) and 19 ft (5.8 m) in length, both of which had been

exposed for 12 years. One month later, the short pile was extracted and examined. Relatively low

corrosion rates calculated from the polarization data were verified by the appearance of the pile and by the limited extent of the pitting. Keywords: Corrosion; corrosion rate; disturbed soil; instantaneous rate; pit depth; pitting factor; polarization; steel piling; undisturbed soil; weight loss.

1 . Introduction

Corrosion observed on structural steel piling exposed to underground environments based on visual inspection and

measurements of pit depth has been described by Romanoff [1].^ His inspections were made in cooperation with

the Corps of Engineers (Lower Mississippi Valley Divi- sion) and the American Iron and Steel Institute. During

the course of an investigation at four dam sites, where

piling had been examined, Romanoff decided to expose

steel pipe specimens, arranged in groups of four, to the same underground environments nearby. One specimen

of each group was wired to enable periodic monitoring of instantaneous rates of corrosion by polarization measurements. The groups of specimens were removed from

each site at intervals of 1, 2, 4, and 7 years. The buried specimens, exposed to back-filled trenches, served a two-fold purpose. Romanoff [1] reported that

steel exposed to excavated soils was subject to more severe corrosion than that which he observed on driven piling for a given environment. Thus, the steel specimens would

provide the opportunity for comparing corrosion under

the two conditions of exposure (driven or buried). Sec- ondly, they offered an excellent chance for evaluating the accuracy and practicability of a polarization technique for measuring corrosion. The method was evaluated by comparing the cumulative metal losses (based on Faraday's

law) of the wired specimens with their actual weight losses.

^ Figures in brackets indicate the literature references at the end of this paper.

Past work has demonstrated that instantaneous rates of corrosion on pipe specimens in situ can be measured by a

polarization technique and averaged for periodic intervals in calculating metal losses resulting from corrosion for a given period of exposure [2] . As exposure time for some

of the Corps of Engineers' specimens extended over a period of 7 years, an excellent opportunity prevailed for

a further evaluation of the technique as applied to underground corrosion. Furthermore, it became possible to monitor corrosion rates at each of the four sites over a period of 7 years. By thus monitoring corrosion rates, the length of exposure time required to obtain reliable performance data of metals exposed to a given environment can be estimated.

Romanoff [1] concluded, based primarily on visual observation and experience, that iron exposed to soil in backfilled trenches is more severely corroded than when

exposed to the same soil (undisturbed). Romanoff re- ferred to undisturbed soil as that soil adjacent to driven

piling below the backfilled soil. In order to further

substantiate this conclusion, Romanoff exposed iron pipe

specimens to excavated trenches in the same areas where

driven piling had previously been visually examined. The

Corps of Engineers, responsible for making the polarization measurements, also exposed iron rods, limited in number, by driving some of them into the soil and by exposing

other identical rods to excavated soil nearby. The National Bureau of Standards prepared weighed pipe speci- mens for the burial program. The rod specimens were 40-107
prepared by the Corps of Engineers. The Corps furnished

the Bureau with copies of the polarization curves obtained

at the periodic intervals. During the period of 7 years, all specimens involved in four removals were sent to the Bureau for cleaning and determination of metal losses. In a recent report [3] by the Corps of Engineers on the corrosion of underground steel piling, the results of measurements made on the pipe and rod specimens are in- cluded. Included in that report are the weight losses and

maximum pit depths on all specimens, pipe and rod, un- wired and wired. Estimated weight losses based on elec- trical measurements are summarized and discussed in relation to what was observed on nearby piling. In this paper, the polarization curves submitted to NBS

by the Corps of Engineers are evaluated by the Bureau. This accounts for any differences (averaging 9% ) between

the Corps estimated weight losses and the calculated weight

losses tabulated herein. Stabilized corrosion rates, based on polarization measurements made on the wired seven- year pipe specimens in back-filled trenches, are expressed

as average penetration and compared with the maximum

corrosion observed on piling at the same sites exposed

from 11 to 20 years. Recently, the writer became aware of some isolated steel pipe piles located on the grounds of a sewage disposal

plant. It was suggested that it might be of interest to make polarization measurements on one or more of the driven piles which were exposed to the soil for 12 years. The results of measurements and calculated rates of cor- rosion for two 12.75 in (32.5 cm) diam piles 72 ft (22 m)

and 19 ft (5.8 m) long are described.

2. Experimental Procedure

2.1. Preparation of Pipe and Rod Specimens

Sixteen pipe specimens were prepared for burial at each

of four sites. The specimens were cut from standard black

iron pipe 1.5 in (3.8 cm) diam to lengths of 14 in (35.5

cm). Loose mill scale was removed and the specimens were deburred, degreased and weighed to the nearest 50

mg. The inside of the pipe was coated with heavy grease and rubber caps were placed over the open ends so as to confine corrosion to the outer surface area 0.5 ft" (4.6

dm-) approx. One of each set of four specimens, consti- tuting a set for removal, was equipped with an insulated copper wire soldered to the inside of the pipe and brought

through a hole in the center of one of the rubber caps. The pipes were placed laterally in the trench about 12 in (30.5 cm) apart and buried horizontally about 3 ft (0.92

m) below the earth's surface. The wires to specimens ter- minated above ground in boxes mounted on wooden posts. The number of rod specimens was limited to two at each of the four sites. One of the rods was exposed vertically positioned in back-filled soil and the other rod was

driven off to the side about 18 in (46 cm) away. The rods were cut from hot-rolled steel 0.75 in (1.9 cm) diam to 3

ft. (0.92 m) lengths. They were cleaned and weighed as previously mentioned for the pipe specimens. Both rods were equipped with insulated copper wires terminating

above ground. The top 5 in (12.7 cm) of each rod. in- cluding the wire connection, was coated with coal tar.

This again left about 0.5 ft^ (4.6 dm^) of bare surface for ] exposure to the soil, the same as for the pipe specimens.

2.2. Polarization Measurements —

Pipe and Rod Specimens

A galvanized steel pipe 1 in (2.54 cm) diam and five

ft (1.5 m) long was driven at each site for use as an

auxiliary electrode. Polarization measurements were made by the Corps of Engineers [3] at intervals of from

3 to 7 months approximately. When making polarization ' measurements in soil environments, it is usually necessary

to use a bridge circuit because changes in measured poten- '

tial caused by the IR drop through the soil may be sufiij cient to obscure changes due to actual polarization. The j Holler bridge circuit, originally described by Holler [4] { and more recently by Schwerdtfeger [5], was used by the i Corps of Engineers at the test sites. For running the | polarization curves, equal increments of current were j applied at one minute intervals.

2.3. Removal of Corrosion Products

from the Specimens

The pipe and rod specimens were returned to the Bureau

j for cleaning after exposure to the soils. They were i scrubbed under hot running water to remove soil and loose j corrosion products. The rubber caps were removed from ; the pipe specimens and grease inside the pipes was melted ! out by applying heat from a torch flame. Following dej greasing, the specimens were immersed in a hot solution i (150 °F) of 10 percent ammonium citrate neutralized with

' ammonium hydroxide. Length of immersion time varied i with the degree of corrosion, being usually not over five hours. Ammonium hydroxide was added as required to

j keep the solution on the neutral to alkaline side. Speci- I mens were intermittently scrubbed with a steel-bristle brush '

to remove corrosion products down to bare metal. The rod i specimens were freed of corrosion products in the same j way. Solder was melted and scraped from those speci- mens which had wire leads. Finally, all specimens were i again weighed to the nearest 50 mg. i

1 2.4. Polarization Measurements on i Pipe Piling in Situ | Polarization curves were obtained on bare pipe piling

driven 12 years previously on property of the Hiawatha

Treatment Plant at Syracuse. N. Y. Measurements were I made on two 12 in diam (30.5 cm) pipe piles, 72 ft j (22 m) and 19 ft (5.8 m) in length. The auxiliary anode | was a third pipe pile driven to a depth of 122 ft (37 m).

The piles were separated by a distance of about 5 ft i (1.5 m). The reference electrode was copper-copper | sulfate placed on the earth's surface at a distance of about

50 ft (15.2 m) from the top of the pile being measured. | An adaptation of the Holler bridge (fig. 1) was used ; by the Bureau to obtain the polarization curves. It will 1 be noted that terminals are provided for inserting other ! control resistors. Rs and Rx, should specimen size or environmental conditions make that necessary. For run- ning the curves on the piling, the 0.5 n balancing resistor i was used and the other balancing resistors were set at

j zero. A 12-volt storage battery supplied the polarizing

,

i 41-108
Rs 7.5A 75A I250A

4-4 A 1-4 A 0.34A

PB(NC)

Figure 1. Circuit used for obtaining polarization curves on piling.

current. A potentiometer was used in the bridge circuit for measuring potential*. The polarization curves were

obtained by applying equal increments of current at one

minute intervals. The increments were previously deter- mined by the applied current necessary to change the potential from 2 to 10 mV.

In addition to polarization, soil resistivity in the vicinity of the piling was measured at depths of 3, 12, and 30

ft (0.91, 3.7, 9.1 m) using the 4-pin Wenner method.

The 19 ft (5.8 m) pile was extracted for examination

and measurement of depth of pits.

3.1.

3. Results and Discussion

Corrosion Rates of Pipe Specimens

in Back-Filled Trenches

In figure 2 are shown typical polarization curves obtained at periodic intervals on the seven-year pipe speci- men at Sardis Dam. Corrosion rates at Sardis Dam were

the lowest of the 4 sites. The cathodic curves are those having breaks indicated by Ip, while breaks in the anodic

curves are shown by the currents Iq. Anodic curves are omitted for data obtained 8-10-60 and 5-1-61 because

there was relatively little or no polarization, indicating a value for the current Iq several times that of the current

Ip. Typical polarization curves obtained on four-year

pipe specimens at the 4 test sites are shown in figure 3. The curves were obtained a few months prior to removal

of the specimens.

All electrical data obtained on the pipe specimens at the 4 sites are shown in tables 1 through 4. The method

used in calculating corrosion currents and metal losses is described in the footnotes of the table. Actual weight

losses, after chemical removal of corrosion products, are

also shown for comparison. Agreement between actual and calculated values is reasonably good. The calculated values are based on the electrochemical equivalent for ferrous iron. With the exception of the Sardis site which

is poorly aerated, where corrosion probably continues in

-OS

- 1.0

-OB

- 1.0

, -03 o

-I.G

-0.6

-0.8 O

ti- -1.0

-0.6

-0.8

- 1.0

I I I 1 1 I I I mill—

4-18-62 -

4-21-64

7-12-67 _

J—I I 1 1 1 III \ i I I mil I I I I I I I I 1

1

.001 .01 .1 I APPLIED CURRENT, mA

Figure 2. Typical polarization curves of underground steel speci- men (C8) during seven years of exposure at Sardis Dam site. # Cathodic O Anodic

-0.6

-Q8

- 1.0

-0.6

-OB

o

> -U2

<

UJ2 -0.6

-04

-OJS

-08

1

1—I I I I lllj 1—I I I I I llj 1—I I I I lll|

SARDIS DAM, SPECIMEN C9(ll-26-63)

BONNET CARRE, SPECIMEN E9(l-l5-64)

In

GRENADA DAM, SPECIMEN 09(11-27-631

BERWICK LOCK, SPECIMEN F9(l-l<l-64)

In

=8 8 8 Bl

'p

J \ I I I I ml I I I I I I ml

.01 .1 I APPiJtD CURRENT. mA10

Figure 3. Polarization curves of underground specimens Nos. 9

after 45 months of exposure at four soil sites. # Cathodic O Anodic

43-109
Table 1. Total corrosion (weight loss) calculated from polarization curves of ferrous pipe specimens

exposed up to 7 years in back-filled trenches at Berwick Lock

Polarizing Currents Exposure Corrosion at break in curv** Corrosion Weight loss time potential current cumulative rlel-Lu-L.uS5U4 Latnodic Anodic Calculated c Actual Date io^ cumulative

days V mA mA mA g g Specimen F4

4-05-60 0

8-23-60 140 -0.780 4.2 21/ 2.8 10

11-16-60 225 .735 2.7 4.2 1.6 15

2-07-61 308 .772 2.8 2.8 1.4 18

5-10-61 400 .762 2.9 4.1 1.7 21 19 Specimen F13

4-05-60 0

8-23-60 140 -0.630 6.0 2Ipd 4.0 14

11-16-60 225 .640 3.0 3.6 1.6 20

2-07-61 308 .657 3.6 4.5 2.0 24

5-10-61 400 .580 5.4 7.4 3.1 30

9-19-61 532 .655 9.0 11.0 4.9 43

1-17-62 652 .625 10.0 14.0 5.8 59

4-25-62 750 .580 6.5 7.6 3.5 70 49 Specimen F9 j 4-05-60 0

8-23-60 140 -0.718 5.6 2/pd 3.7 13 11-16-60 225 .630 3.6 3.6 1.8 19

2-07-61 308 .700 3.1 4.4 1.8 23

5-10-61 400 .645 7.0 8.0 3.7 29

9-19-61 532 .665 6.8 7.5 3.6 40

1-17-62 652 .642 8.0 11.0 4.6 53

4-25-62 750 .577 8.0 9.4 4.3 64

8-29-62 876 .564 7.6 9.6 4.2 78

1-16-63 1016 .620 9.0 9.0 4.5 93

5-15-63 1135 .415 6.0 4.5 2.6 103

9-18-63 1261 .552 3.5 3.5 1.7 110

1-14-64 1379 .575 2.7 3.2 1.5 115

4-28-64 1483 .533 4.0 4.0 2.0 119 67

Specimen F8

4-05-60 0

8-23-60 140 -0.628 7.4 21pd 4.9 17 11-16-60 225 .638 3.0 3.7 1.7 24

2-07-61 308 .635 5.2 4.3 2.3 28

5-10-61 400 .635 11.5 10.0 5.3 37

9-19-61 532 .660 7.5 6.5 3.5 51

1-17-62 652 .553 10.0 10.0 5.0 64

4-25-62 751 .578 6.8 6.6 3.3 74

8-29-62 877 .587 13.0 13.0 6.5 90

1-16-63 1017 .613 13.0 12.0 6.2 112

5-15-63 1136 .417 4.5 4.0 2.1 124

9-18-63 1262 .560 4.5 5.2 2.4 131

1-14-64 1380 .553 3.7 5.0 2.1 138

4-28-64 1484 .500 4.5 4.5 2.2 143

9-09-64 1618 .337 3.4 3.4 1.7 150

12-17-64 1717 .556 2.0 2.0 1.0 153

5-04-65 1856 .450 1.2 2.4 0.8 156

1-11-66 2180 .531 1.2 1.4 0.6 161

5-17-66 2235 .530 0.6 1.0 0.4 162

10-25-66 2396 .545 0.7 1.4 0.5 164

7-25-67 2669 .328 0.9 0.7 0.4 167 125

a See figure 2.

cFrom Faraday's law. Weight loss (grams) = A^tio, where /C = electrochemical equivalent 2.8938 X 10" g/c, t = time (s) for the period between successive readings, Jo= average current (amperes) for a period. Approximately, weight loss (mg)=25 t io, where t = days between successive measurements, £o = average current (mA) between successive measurements. The values of io at the beginning and

at the end of exposure are taken as the initial and final values, respectively, as calculated. d Breaks are indefinite. Values are based on relative cathodic and anodic polarization and/or values of before or after. 43-110
Table 2. Total corrosion (weight loss) calculated from polarization curves of ferrous pipe specimens

exposed up to 7 years in hack-filled trenches at Bonnet Carre Spillway

Date

time

/Nil i^UIllUlallVC miiIqIii^^ potential

Polarizing Currenta

at break in curve Corrosion

current

tob

Weight loss

Cathodic h

Anodic

!<,

Calculatedc cumulative

Actual

days V mA mA mA g g Specimen E4

4-06-60

8-24-60 11-17-60

2-08-61

5- 11-61

0 140 225 308

400

-0.800

.780

.770

.780

3.0 2.9

2.6

3.0

7.0

7.3 2.5 /y

2.5 7^

2.0

2.1

1.9 2.1

7

111520 12 Specimen E13

4-06-60 0

8-24-60 140 -0.822 2.7 2 IpA 1.8 6

11-17-60 225 .786 2.3 2.5 /yl 1.7 10

2-08-61 308 .775 2.8 2.5 fp 2.0 14

5-11-61 400 .790 2.8 2.5 U 2.0 s

9-20-61 532 .790 2.8 2.5 fj, 2.0 25

1-18-62 652 .777 2.7 6.7 1.9 31

4-26-62 750 .770 3.0 8.5 2.2 36 21 Specimen E9

4-06-60 0

8-24-60 140 -0.806 2.8 2 /pd 1.9 7

11-17-60 225 .790 3.2 2.5 Tpd 2.3 11

2-08-61 308 .780 2.9 2.5 /; 2.1 16

5-11-61 400 .800 3.5 2.5 Tp 2.5 21

9-20-61 532 .799 3.1 2.5 4 2.2 29

1-18-62 652 .790 3.1 7.8 2.2 35

4-26-62 750 .800 3.0 8.4 2.2 41

8-30-62 876 .771 6.4 7.2 3.4 50

1-17-63 1016 .750 4.4 5.7 2.5 60

5-16-63 1135 .545 3.0 3.0 1.5 66

9-17-63 1259 .650 2.4 2.5 1.2 70

1-15-64 1379 .710 1.7 2.0 0.92 73

4-29-64 1483 .690 2.1 2.8 1.2 76 41 Specimen E8

4-06-60 0

8-24-60 140 -0.812 2.8 2 Tpd 1.9 7

11-17-60 225 .790 3.2 2/p 2.1 11

2-08-61 308 .775 3.6 9.0 2.6 10

5-11-61 400 .795 4.6 2 Zpd 3.1 22

9-20-61 532 .790 3.5 9.0 2.5 32

1-18-62 652 .787 3.4 8.0 2.4 39

4-26-62 751 .780 4.2 12.0 3.1 45

8-30-62 877 .684 8.6 9.0 4.4 57

1-17-63 1016 .680 4.9 5.6 2.6 69

5-16-63 1135 .565 1.7 3.5 1.1 74

9-17-63 1259 .628 1.5 3.1 1.0 77

1-15-64 1379 .640 1.6 1.9 0.9 80

4-29-64 1483 .620 2.0 2.0 1.0 83

9-10-64 1617 .600 1.9 2.1 1.0 86

12-18-64 1716 .559 1.4 1.9 0.8 88

5-05-65 1855. .488 1.3 1.9 0.8 91

1-12-66 2107 .638 1.1 0.8 0.5 95

5-18-66 2234 .600 0.8 1.4 0.5 96

10-26-66 2395 .563 0.9 1.2 0.5 98

7-26-67 2668 .530 1.1 1.1 0.6 102 71

a See figure 2.

cFrom Faraday's law, Weight loss (grams) < io, where K= electrochemical equivalent 2.8938 X 10"" g/c, i =time (s) for the period between successive readings, to= average current (amperes) for a period. Approximately, weight loss (mg) =25 i io, here i = days between

successive measurements, io= average current (mA) between successive measurements. The values of I'o at the beginning and at the end of exposure are taken as the initial and final values, respectively, as calculated. dBreaks are indefinite. Values are based on relative cathodic and anodic polarization and/or values of /g before or after.

A4-111
Table 3. Total corrosion (weight loss) calculated from polarization curves of ferrous pipe specimens

exposed up to 7 years in back-filled trenches at Grenada Dam

Date

Exposure

time cumulative

Corrosion

potential

Ket-Lu-LubU4

Polarizing Current^

at break in curve Corrosion

current

b

Weight loss

Cathodic Anodic

I,

Calculatedc cumulative

Actual

days V mA mA mA g g Specimen D4

3-30-60 8-11-60

11-02-60

2-16-61

5-03-61

0

134 217

323 399

-0.408

.403 .444

.437

1.9 2.0 3.3 4.02.9

2.2

4.1 8.3

1.1 1.0 1.8 2.7

3.7 5.9 9.6 14 17

Specimen D13

3-30-60 0

8-11-60 134 -0.452 4.0 4.5 2.1 7 11-02-60 217 .483 2.2 4.0 1.4 11 2-16-61 323 .588 7.0 13.0 4.5 18

5-03-61 399 .560 7.5 9.7 4.2 27

9-07-61 526 .457 4.5 5.6 2.5 37

1-26-62 667 .473 5.0 6.4 2.8 47

4-19-62 750 .500 6.0 6.6 3.1 53 40

Specimen D9

3-30-60 0

8-11-60 134 -0.467 2.6 2.7 1.3 4

11-02-60 217 .433 2.7 3.9 1.6 7 2-16-61 323 .630 4.3 6.0 2.5 13 5-03-61 399 .662 4.3 4.3 2.2 17

9-07-61 526 .495 4.8 5.6 2.6 25

1-26-62 667 .725 3.1 3.5 1.6 32

4-19-62 750 .725 2.4 2.6 1.2 35

9-06-62 890 .265 4.2 5.9 2.4 42

12-12-62 987 .169 2.4 2.5 1.2 46

4-04-63 1100 .501 4.2 4.2 2.1 51

8-29-63 1247 .550 11-27-63 1337 .425 2.5 2.1 1.1 60

4-22-64 1483 .610 2.0 2.0 1.0 64 63

Specimen D8

3-30-60 0

8-11-60 134 -0.388 1.9 3.0 1.2 4

11-02-60 217 .390 2.2 2.5 1.2 6

2-16-61 323 .447 3.5 3.9 1.8 10

5-03-61 400 .457 4.6 5.2 2.4 14

9-07-61 528 .387 3.0 8.0 2.2 22

1-26-62 669 .437 3.8 5.5 2.2 30

4-19-62 752 .465 2.7 5.2 1.8 34

9-06-62 892 .230 3.0 4.0 1.7 40

12-12-62 989 .132 1.7 2.6 1.0 43

4-04-63 1102 .358 3.0 4.3 1.8 47

8-29-63 1249 .384 2.0 2.2 1.0 53

11-27-63 1339 .403 1.3 1.9 0.8 55

4-22-64 1485 .379 1.2 1.1 0.6 57

8-26-64 1611 .382 0.8 1.2 0.5 59

1-13-65 1751 .366 0.5 0.8 0.3 60

4-29-65 1858 .359 0.5 0.7 0.3 61

12-08-65 2081 .390 0.3 0.4 0.2 62

5-11-66 2235 .373 0.3 0.5 0.2 63

10-12-66 2389 .127 0.2 0.3 0.1 63

7-13-67 2663 .406 0.4 0.4 0.2 64 55

a See figure 2.

c From Faraday's law, Weight loss (grams) = K t io, where A" = electrochemical equivalent 2.8938 X 10"^ g/c, « = time (s) for the period between successive readings, io = average current (amperes) for a period. Approximately, weight loss (mg) = 25 t io, where i = days between

successive measurements, io = average current (mA) between successive measurements. The values of io at the beginning and at the end

of exposure are taken as the initial and final values, respectively, as calculated.

45-112
Table 4. Total corrosion (weight loss) calculated from polarization curves of ferrous pipe specimens

exposed up to 7 years in back-filled trenches at Sardis Dam

Liate

Exposure

time cumulative

Corrosion

potential Ref-Cu-CuS04

Polarizing Current a

at break in curve Corrosion

current

Weight loss

Cathodic

//> Anodic Calculated c cumulative

Actual

days V mA mA mA 6 g Specimen C4

3-29-60

8-10-60 11-01-60

2-15-61 5-01-61

0 134 217

323 398

-0.821

.802

.800

.795

0.54

.16

.11 .09

9/^d

9fp

0.54

.14

.10

.08

1.8

2.5 2.8

3.0 4.3 Specimen C13

3-29-60 0

8-10-60 134 -0.815 0.86 > V 0.86 2.9 11-01-60 217 .806 .35 .31 4.1 2-15-61 323 .800 .25 9fp .22 4.8

5-01-61 398 .795 .22 9Ip .20 5.2 9-06-61 526 .799 .32 9i; .29 6.0

1-25-62 667 .803 .16 9i; .14 6.7 4-18-62 750 .800 .20 9/; .18 7.1 6.0 Specimen C9

3-29-60 0

8-10-60 134 -0.815 0.58 > V 0.58 1.9 11-01-60 217 .808 .28 .25 2.8 2-15-61 323 .805 .11 9i; .1 3.3 5-01-61 398 .800 .11 9Ip .1 3.5 9-06-61 526 .800 .09 9fp .08 3.7 1-25-62 667 .806 .10 9Ip .09 4.0 4-18-62 750 .812 .10 9Ip .09 4.2 9-05-62 890 .800 .08 9fp .08 4.5 12-11-62 987 .770 .13 9lp .12 4.8 4-03-63 1100 .804 .09 9Ip .08 5.0 8-28-63 1247 .830 .06 9fp .06 5.3 11-26-63 1337 .797 .06 9Ip .05 5.4 4-21-64 1483 .800 .04 9i; .03 5.6 4.6

Specimen C8

3-29-60 0

8-10-60 133 -0.828 0.68 0.68 2.3 11-01-60 216 .810 .27 9/pd .24 3.2 2-15-61 322 .810 .14 9Ip .13 3.7 5-01-61 397 .802 .14 9Ip .13 3.9 9-06-61 525 .805 .13 O.i .10 4.3 1-25-62 666 .808 .12 .8 .11 4.6 4-18-62 749 .808 .11 1.2 .10 4.8 9-05-62 889 .799 .10 1.0 .09 5.2 12-11-62 986 .782 .08 0.8 .07 5.4 4-03-63 1099 .790 .05 0.3 .04 5.6 8-28-63 1246 .830 .04 '•^^

.04 5.7 11-26-63 1336 .792 .04 .03 5.8 4-21-64 1481 .790 .03 .1 .02 5.9 8-25-64 1607 .799 .03 .02 5.9 1-12-65 1747 .790 .02 OU .02 6.0 4-28-65 1854 .800 .02 .6 .02 6.1 12-07-65 2078 .787 .01 .4 .01 6.1 5-10-66 2232 .790 .02 .5 .01 6.2 11-11-66 2417 .790 .02 .5 .01 6.2 7-12-67 2660 .797 .02 .6 .02 6.3 4.8

a See figure 2.

c From Faraday's law, Weight loss (grams) =Kt io, where electrochemical equivalent 2.8938 X 10~* g/c, f = time (s) for the period between successive readings, io = average current (amperes) for a period. Approximately, weight loss (mg) =25 t to, where t = days between

successive measurements, io = average current (mA) between successive measurements. The values of to at the beginning and at the end

of exposure are taken as the initial and final values, respectively, as calculated. d Breaks are indefinite. Values are based on relative cathodic and anodic polarization and/or values of Ig before or after.

46-113
the ferrous state, the use of the ferric equivalent might

be more valid. The use of the ferric equivalent would

reduce the calculated weight losses by one-third. The corrosion potentials at Sardis (table 4) were con- tinuously around 0.8 V, while at other sites the potentials

fluctuated and were generally more positive. The high water table at Sardis probably accounted for the relatively

high electronegative potentials indicative of a deficiency

in oxygen. Poor aeration could also account for the low

corrosion rates at the Sardis site.

3.2. Comparison of Corrosion on Pipe Specimens

and on Piling in the Same Soils Cumulative weight losses based on polarization curves obtained on the seven-year specimens at the 4 sites are

plotted against time in figure 4. These losses after 3.7 years of exposure are converted to corrosion rates ex- pressed as weight loss and average penetration (reduction

in cross section ) for each site. Corrosion rates are tabulated in table 5 for comparison with corrosion observed on piling at the sites. The maximum reduction in thick- ness shown for the piling is not an overall average based on weight loss but is based on the average depth of the 25

deepest pits measured in the most corroded spots over an

area 1 in" (6.5 cm") on the piles and includes both sides of the piling wall. Had the maximum reduction in thick- ness been based on metal loss for a larger area, such as

that of the pipe specimen 72 in" (4.6 dm^) , the percentages

shown in table 5 would be considerably lower. The corrosion data (table 5) pertaining to the pipe

specimens, under conditions conducive to maximum rates

140

E

D& 120

:oo

5 80

60

40

500 1000 1500 2u00 EXPOSURE TIME, days

250C ^000

Figure 4. Weight loss-time curves, based on polarization curves, obtained on iron specimens (Nos. 8) buried at four back-filled trench sites.

of corrosion, show that corrosion is not a serious problem on piling in these particular locations. Pitting is not a

limiting factor as it is on pipe lines. Thus, for example,

at Berwick Lock (the most corrosive site) the average

penetration on the pipe specimens after 3.7 years of exposure was at a rate of about 0.00078 in/yr (20 micrometers/yr). This means that on the piling of 0.375 in (0.95 cm) metal thickness, if corrosion were to occur on

both sides in the same area at this rate only 10 percent of the metal thickness would be gone in 24 years. This cor- rosion would be in the area subject to the severest corrosion, that is, at the water table or in the excavated soil. In these areas on piling, the Corps of Engineers [3] considers a 35 percent reduction in cross section over a 50- year period as an acceptable maximum. At Berwick Lock, even taking into consideration the higher corrosion rate on

specimens during the first 3.7 years, the average reduction

in wall thickness over a 50-year period would still be

under 30 percent, assuming that piling corroded at the same rate.

3.3. Polarization Measurements on Driven and

on Buried Steel Rods

Electrical measurements on the rods are tabulated in tables 6 through 9. During early exposure, corrosion cur- rents on the buried rods were larger than on the driven

rods. As time went on, corrosion currents tended to equalize, except perhaps at Bonnet Carre and at Berwick

Lock where corrosion rates on the buried rods appear to be significantly greater than those on the driven rods. The potentials of the driven rods are apparently less affected by oxygen than are the potentials of the buried

rods. A deficiency of oxygen tends to make the corrosion

potentials more electronegative. It is interesting to correlate potential changes with pitting on the rods. As re- ported by the Corps of Engineers [3], except at Sardis

Dam, it was observed that the pits were several times

deeper on the buried rods than on the driven rods. Such

differences were greatest at Bonnet Carre and at Berwick

Lock where the differences in corrosion potentials between

buried and driven rods was also greatest, the buried rods

having potentials which fluctuated to more positive values. The data [3] indicate that the pitting factor (ratio of maximum pit-depth to average penetration) is greater on

buried structures than on driven structures. At Sardis

Dam this difference was negligible because of the high

water table. The data suggest that future experiments

along similar lines should be carried out with longer rods.

3.4. Corrosion Rates of Pipe Piles as Calculated from Polarization Curves

The Hiawatha Treatment Plant processes sewage for the area of metropolitan Syracuse, N. Y., where the water

table is said to be about 10 ft (3 m) from the ground

surface. Soil resistivities in the vicinity of the test piles as measured by the 4-pin method at pin spacings of 3 ft (0.91 m), 12 ft (3.7 m), and 30 ft (9.1 m) were respectively, 10,300, 3450 and 800 n-cm.

Preliminary polarization indicated that current incre- ments of 40 mA would be satisfactory for obtaining the cathodic polarization curve on the 72 ft (22 m) pile (fig.
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Figure 5. Polarization curves of a bare pipe pile, 12.75 in O.D. X 72 jt. long (32.5 cm X 22m) after underground exposure for 12 years at the Hiawatha treatment plant, Syracuse, N. Y.

5) . The following day, the anodic curve was also obtained

by using the same increments of applied current. Both

curves are shown plotted on rectangular coordinates in order to verify changes-in-slope (breaks). Based on the Pearson equation [2J, the total corrosion current on the bare metallic piling surface was calculated to be 215 mA,

or a corrosion rate of 0.9 mA/ft" (0.097 mA/dm^).

Upon learning that one of the other piles in the vicinity

(about 5 ft or 1.5 m away) was of the same diameter but only 19 ft (5.8 m) long, the thought occurred that the average corrosion rate of the shorter pile ought to be

greater than that cf the long pile because a larger percent- age of the short one was probably exposed to excavated

soil during installation. Time permitted running a ca- thodic curve on the 19 ft (5.8 m) pile, applied current in- crements (10 mA) being estimated in the same manner as previously (fig. 6). Time did not permit obtaining the anodic polarization curve; however, it seemed reasonable

to assume that the Ip/Iq ratio would be similar to what was previously observed for the long pile. Based on this assumption, the average corrosion current was calculated

to be 79 mA and the corrosion rate 1.3 mA/ft^ (0.14

mA/dm^) . Because of the limited data, it could be argued

that the corrosion rates of the two piles might not be

significantly different, and rightly so. Nevertheless, the second pile measurements add validity to the corrosion

rate calculated for the long pile. Validation of the corrosion rate was further emphasized when the continuous

application of 400 mA to the long pile for one hour caused

a change in potential of 50 mV, confined strictly to polarization. This indicated that the pile (fig. 5) was being

cathodically protected and that the current at the break,

about 300 mA, was in excess of the corrosion current

(calculated to be 215 mA).

On the basis of soil resistivity as measured in the area where the piles are located, it appears that the greater

portion of the 72 ft (22 m) pile is driven into soil having

a resistivity of 800 fi-cm or less. To further validate the corrosion rate measurements made on the piling other information can be mentioned. The corrosion rates of plain ferrous pipe specimens, based on actual weight loss- time curves involving hundreds of specimens after five years of exposure in 28 soil sites having resistivities be- tween 500 and 3000 fi-cm, averaged 1.6 mA/ft^ [6] (0.17 mA/dm^). The specimens had been buried in

back-filled trenches (disturbed soils)

.

One month after making the polarization measurements,

the 19 ft (5.8 m) pile was extracted and cleaned for the measurement of pit depths. It was found that 40 to 50

percent of the pile surface was still covered by mill scale

after 12 years of exposure. Pitting on the remaining sur- face was scattered. By far, most of the pitting was in the upper 9 ft (2.75 m). Thirty-four pits ranging in depth from 50 to 100 mils (1.3 to 2.6 mm) were found in the upper 9 ft (2.75 m), most of the other pits being less than 30 mils (0.77 mm). In the lower 10 ft (3.05 m) of the pile, ten pits ranging from 30 to 90 mils (0.77 to 2.3 mm) were observed. Pits less than 30 mils (0.77 mm)

were not recorded. Assuming that piling at the Syracuse Plant corrodes at the rate of 1.3 mA/ft^ (0.14 mA/dm^) for 50 years, the average reduction in metal thickness is of interest. A

current density of 1.0 mA/ft^ (0.11 mA/dm^) is approximately equivalent to an overall reduction in wall thickness

of 0.5 mils/yr (13 micrometers/yr ) . Thus, the corrosion

current density of 1.3 mA/ft^ (0.14 mA/dm^) for 50

years would cause a reduction in pipe wall thickness of about 33 mils (0.85 mm). As the wall thickness of the pipe under discussion is 0.375 in (9.5 mm), the overall reduction in thickness for 50 years would be less than 9

percent. As previously mentioned, the Corps of Engineers |3j considered a 35 percent loss in cross section as

the acceptable maximum for 50 years. Were a similar

rate of corrosion taking place on two surfaces (for example on H piling), the reduction in wall thickness would

still be within the acceptable maximum.

08 .12 ,16 .20 .24 APPLIED CURRENT, A

Figure 6. Polarization curve of a bare pipe pile, 12.75 in O.D. X 19 ft. long (32.5 cm X 5.8 m), after exposure underground for 12 years at Hiawatha treatment

plant, Syracuse, N. Y. 53-120
4. Conclusions

Polarization curves obtained by the Corps of Engineers

(Lower Mississippi Valley Division) on four wired pipe

specimens at each of four underground test sites were

evaluated by the National Bureau of Standards for accuracy in the calculation of metal loss attributable to corrosion and as a means of estimating corrosion on piling

which had been previously examined and exposed to the same environments. At each test site one specimen

(wired) along with three identical steel unwired speci- mens were removed after 1, 2, 4 and 7 years of exposure. The Corps of Engineers periodically had made cathodic

and anodic polarization measurements on the wired

specimens at intervals varying from 2 to 7 months. Using

the changes-in-slope (breaks) in the curves plotted on

semi-logarithmic coordinates, the calculated instantaneous

rates of corrosion were converted to total metal losses by

averaging rates for the intervals. The calculated metal

losses were in reasonable agreement with the actual weight

losses of the wired specimens and also with the weight

losses of the unwired specimens.

The relatively stable rates of corrosion which were ob- served after about four years of exposure of the wired

7-year pipe specimens are expressed as average penetration (reduction in metal thickness) and compared with

the corrosion visually observed on piling in the same area

or soil environment. On the basis of a criterion mentioned

by the Corps of Engineers and using average penetration

rates at the most corrosive of the four sites it was con- cluded that the corrosion taking place on the bare piling was not a serious problem from the standpoint of loss in structural strength.

Corrosion which had taken place in five years on driven

steel rods was compared with the corrosion on identical rods exposed concurrently in nearby excavated soil. The

corrosion potentials, measured periodically on the rods in connection with polarization runs, seem to bear some

relation to the maximum pit depths reported by the Corps

of Engineers. Pits were several times deeper on the buried

rods than on the driven rods at the two most corrosive

sites where the buried rods fluctuated in corrosion potential

to values more electropositive than those of the driven

rods. While rod specimens were limited in number, one

driven and one buried at each of the four sites, the data

do indicate that pitting is deepest on the metal in contact with excavated soil above the water table. The differ- ences in weight losses of driven and buried rods were not always significant; however, the metal losses on the driven

rods were generally less. Cathodic and anodic polarization curves were obtained on two 12 in (32.5 cm) diam pipe piles, 72 ft (22 m) and

19 ft (5.8 m) in length, driven 12 years previously at a sewage disposal plant. The 72 ft (22 m) pile was ex- posed to soil varying in resistivity from 800 O-cm for the greater part to 10,300 fZ-cm near the surface. Instan- taneous corrosion rates were calculated from the curves. Based on the pipe wall thickness 0.375 in (0.95 cm) the

average reduction in wall thickness of the short pile over a period of 50 years would be less than 9 percent. The

polarization curves indicated that the long pile was corroding at a lower rate than the short one; however, as only two piles were involved, the difference may be insignifi- cant. About one month later, the short pile was extracted and examined for general corrosion and pitting. It was

found that about 40-50 percent of the surface was still covered with mill scale. Most of the pits under 30 mils

(0.77 mm) in depth were in the upper 9 ft (2.75 m) of

the pile with 34 pits ranging in depth from 50 to 100 mils

(1.3 to 2.6 mm). Only two pits were 100 mils (2.6 mm)

deep.

The author is deeply indebted to his former associate Melvin Romanoff (deceased) who made the arrangements

with the Corps of Engineers to carry out the visual inspec- tion of piling at the dam sites and the electrical measure- ments on pipe specimens at the sites. The financial support of the American Iron and Steel

Institute is gratefully acknowledged.

Deserving special recognition is E. Harold Ardahl,

U.S. Army Engineer District, Lower Mississippi Valley

Division, Vicksburg, Miss., who carried out all electrical measurements on the pipe and rod specimens and together

with Mr. Romanoff made physical inspections on exca- vated and extracted piles at the dam sites. The author extends his thanks to 0. W. Wade, ConsuUant, who instigated making polarization measurements on

isolated piling at the Hiawatha Treatment Plant, Syracuse, N. Y. and for his assistance in performing the measurements. Mr. Wade later evaluated the corrosion on one of the extracted piles.

5. References

[1] Romanoff, Melvin, Corrosion of steel pilings in Soils, Nat. Bur.

Stand. (U.S.), Monogr. 58, 23 pages (Oct. 1962).

[2] Schwerdtfeger, W. J., A study by polarization techniques of the corrosion rates of aluminum and steel underground for sixteen months, J. Res. Nat. Bur. Stand. (U.S.), 65C (Eng. and Instr.), No. 4, 271-276 (Oct.-Dec. 1961).

[3] Corps of Engineers-Lower Mississippi Valley Division, Vicks- burg, Miss., Report on Corrosion of Underground Steel

Piling, December 1969.

[4] Holler. H. D., Studies on galvanic couples 1. Measurement

of electromotive force and internal resistance of cells dur- ing current flow, J. Electrochem. Soc. 97, 271 (Sept. 1950) ; Corrosion 7, 52 (Feb. 1951).

[5] Schwerdtfeger, W. J., Current and potential relations for the cathodic protection of steel in a high resistivity environment,

J. Res. Nat. Bur. Stand. (U.S.) 63C (Eng. and Instr.). No. 1, 37-45 (July-Sept. 1959).

[6] Schwerdtfeger, W. J., Soil resistivity as related to under- ground corrosion and cathodic protection, J. Res. Nat. Bur.

Stand. (U.S.), 69C (Eng. and Instr.). No. 1, 71-77 (Jan.- Mar. 1965).

(Paper 75C2-320)

54-121

NBS~114A (i--/-!) 2. Gov't Accession

No.

U.S. DEPT. OF COMM. BIBLIOGRAPHJC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS-MN-127

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

*ISelected MBS Papers on

Underground Corrosion of Steel Piling

5. Publication Date March 1972

6. Performing Organization Code

7. AUTHOR(S) 8. Performing Organization W. J. Schwerdtfeger., & _ Romanoff

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 3120143

11. contract/Grant No.

12. Sponsoring Organization Name and Address Steel Pile Subcommittee

American Iron and Steel Institute

150 East Forty Second Street

New York, New York 10017

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

Supersedes NBS Monograph 5S

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) TMs monograph is a collection of published papers on underground corrosion of steel

piling. The papers are as follows:

(1) Romanoff, Melvin, Corrosion of Steel Pilings in Soils, Nat. Bur. Stand. (U.S.)

Monogr. 58, (Oct. 1962).

(2) Romanoff, Melvin, Corrosion Evaluation of Steel Test Piles Exposed to Permafrost

Soils, Proceedings 25th Conference, National Association of Corrosion Engineers,

page 6 (March 1969).

(3) Romanoff, Melvin, Performance of Steel Pilings in Soils, Proceedings 25th Conference,

National Association of Corrosion Engineers, page 14 (March 1969).

(4) Schwerdtfeger , W. J. , Polarization Measurements as Related to Corrosion of Underground Steel Piling, J. Res. Nat. Bur. Stand. (U.S.), 75C (Eng. and Instr.) No. 2,

107-121 (April-June 1971).

The papers describe corrosion of various types of steel piling exposed underground in

the United States under climatic conditions ranging from semi-tropical to frigid. Cortrosion is described on driven piling above and below the water table after many years of

2xposure in soils having resistivities between 78 and 50,000 ohm-cm and ranging in pH

Erom 2.3 to 8.8.

One of the papers demonstrates the value of a polarization technique in measuring

corrosion. Polarization data were obtained on weighed steel pipe specimens exposed underground for seven years in backfilled soil trenches in the vicinity of driven sheet piling

rhe technique was evaluated by comparing calculated cumulative weight losses of specimens

ffith their actual weight losses. The technique was also shoxm to be applicable to under-

?roimd pipe piling.

17. KEY WORDS (Alphabetical order, separated by semicolons) Active region; aerated soil; corrosion;

disturbed soilj excavated; extracted: H-piling; instantaneous corrosion rate; mill scale;

jermafrost regron; pipe piling; pit depth; polarization; sheet piling; undisturbed soil;

jeight loss.

18. AVAILABILITY STATEMENT

PCl UNLIMITED.

I I FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

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21. NO. OF PAGES

63

22. Price

;.65

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