"0V5 1962

NBS MONOGRAPH 58

Corrosion of

Steel Pilings in Soils

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
1

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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

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. - Price 20 cento
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. SoU characteristics and properties 3

3.4. Thickness measurements 4

4. Results of inspections 4

4.1. Extracted pUes 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,

Ai'kansas 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 J

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 piUngs which have been in service in various underground 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, bulldieads, 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 structures along the

Mississippi River to expose sheet steel pilings which

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

and sections of the piles were retiu-ned to the laboratory for fiu-ther 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, 1962.

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 investigation will 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 dming 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 structure or actual

measurements relating to the condition of the pUes

examined.

Statements regarding the underground 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 yr have shown

upon removal that corrosion did not penetrate more

than %i 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 foimdations in bridge structm'es in Nebraska. They found little, if any, corrosion at depths

greater than 18 in. below the stream bed or ground

water level. It was estimated 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
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 pile 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 ground, 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 maxunum depth of Kb in. were observed

on the shell below ground water. Slightly more

pitting was found in the zone above ground-water

level; the average depth of the pits was again about

Ke in.

It was found on examination of steel sheet piling

which was removed after exposiue 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 during most

of the year the river contained some free siilfuric

acid.

In a report concerned with a study of the expected

life of steel H -piling and thin wall cylinder piling

under highway structiues in the Texas Gulf Coast

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

of muck and peaty soUs, 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-pile 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 pUe 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-pUe which was

extracted 17 yr after installation at Bonnet Carre

Spillway in Louisiana. A discussion of the condition

of this pile 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 occurred in the area

of the splash zone above the high-water mark.

The averages of the original pile thicknesses and

the extent of maximiun corrosion on the piles at

and below the mud line arc 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 ceUs.

Lipp [11] observed from a survey of sheet steel

pile 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 structures

as jetties, groins, harbor, and beach bulkheads. In

a report [12] pertaining to the behavior of %-in.

steel pile groins at Pahn 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 !> Min « Avg Min Avg Min Avg Min Avg Min Avg Min

ft Mud line 0 -1

-3

78.1 92.8 81.663.7 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

a 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 m the specihed
exposvire, 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 %-m. 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.

Rayner 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 aU practical purposes being negligible for

piJiQgs covered on both sides. Four groups of piles were puUed from moderately polluted sea water locations 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 pUes 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 puUed 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 ohin-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 soU,

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 hne. Corrosion above or below this zone on the remaiaing 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 existuig 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 piliags which have been in service in a variety of soil environments.

The soil and corrosion products were removed

from the exposed pUing 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, approxunately 1 ft by

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

amount of corrosion at each location. The removed

portions were shipped to the Vicksburg District

Foundation and Materials Branch Laboratory of

the Corps of Enguieers, 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 pidled

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 boriag data for the excavations at Bonnet

Carre Spillway, Grenada Dam Spillway, Wihnington

Marine Terminal, and Sparrows Point. Soil samples removed from the pile surfaces were shipped to the National Bureau of Standards laboratory for

measurements of soil resistivity and pH; 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-pm 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 soU

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 tune of the pile inspection and at

approximately 15 day intervals thereafter for a

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

the many determinations.

During excavation of the test holes, samples of

undisturbed soil, each sample having a voliune 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 type,

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

measiurements made by means of calipers in the pUe

zone indicated, and takes into account corrosion on

the two sides of the pile siu-face.

Average thickness measurements on the piles inspected 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 represent the average reduction in pile tliickness of the

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

4. Results of Inspections

Historical facts pertaining to the steel pilings of j various structures, the characteristics of the soUs,

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 tliickness refers to this limitation.
4.1. Extracted Piles

a. Bonnet Carre Spillway, New Orleans, Louisiana

History:

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

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 silty 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

ft + 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 oj 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, nless otherwise noted.

All elevation values in the paper refer to msl,

b. H -Piles at Sparrows Point, Maryland

History:

In 1942, several 14-in. H -piles having an average

flange thiclmess of 0.55 in. were driven at the Sparrows 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 OTiter

to inspect and report on the condition of the 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 oj 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 stiff clay.

Soil resistivity and pH

Pile No. Elevation Resistivity

ft 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 G. 3

-83 1, 370 6. 3

* -92 2, 100 6. 4

102 7, 200

120 12, 400 6. 4

II-S -1 1, 130 G. 6

-4 4, 000 4. 7

-24 2, 500 4. 9

-51 1, 4.50 6. 8

-92 2, 500 G. 1

•Laboratory measurements made on soil samples taken from extracted pile.

.4.11 other measurements made on soil sample borings obtained 1 ft from pile.
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 reported are the maximum

observed on the two piles.

+ 13 to +8 ft: Slight uniform corrosion and isolated pitting. Maximum depth of pitting, 35 mils.

At least 50 percent of the mill scale was intact.

Maximimi reduction in flange thickness, 3 percent.

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

corrosion on both piles. 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-ft 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 mils 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 mthin 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.

The reduction in pile thickness due to corrosion

tapered off rapidly as the distance away from the

water fine was increased. The average reduction

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 siu-faces. Neghgible metal attack and localized 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. —11 to —115: No measm-able pit depths. Mill

scale intact over 95 percent of surface. — 115 to —118: At this depth the piles passed

through a sand and gravel stratum. The steel

sm'faces were uniformly corroded and contained

many localized pits which generally ranged in depth

up to 50 mils; 12 pits measured between 50 and 65

mils and 2 pits had depths of 80 and 95 mils. The

average reduction in flange thickness measm'ed 9

and 4 percent, respectively, for pile I-S and for

pile II-S. — 118 to —126: Practically unaffected by cor- rosion. Mill scale more than 95 percent intact.

Figure 1 shows the condition of pile II-S at three

different levels.

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

Arkansas

History:

An end pile was pulled from the upstream abutment wall of the Corps of Engineers, Dam and Lock

No. 8 on the Ouachita River near El Dorado, Ark.

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

Left, vatcr table zone consisting 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.

j'
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 of 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 percent 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

Ohtti—c 7/z 2,900 (Shepard Canes).

3,200 (Laboratory)

1,540 (Laboratory)

1,540 (Laboratory)

4. 3

6. 2

4. 6

Condition of 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 occiured 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 pHe,

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 figiu-e 2.

d. Grenada Dam Spillway, Grenada, Mississippi

History:

A type A sheet pile was pulled for examination

from the end of the north upstream wingwall 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

FIGUKK2. Sandblasted 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.

Tlie section was exposed about 18 ft below

the ground line and it is tlie 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

ft 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)

4. 9

4. 9

3. 6

657852—62 2 7
Figure 3. Sections {1.5 ft 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: Natmal 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 oj 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 thiclmess.

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

measiu-able 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

History:

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 oj piling: 20.5 years

Piling 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)...

3. 0

2. 9

8
Condition oj files:

Metal attack occurred in tlie 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, Louisiana

History:

In connection with construction work on the

Simpson-Long Bridge across Chef Menteur Pass on

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

Orleans, it was necessary to pull about 60 tons of

s'heet steel pilings. The pilings formed a retaining

wall for the abutment of tlie bridge. The sheet piles 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 oj piling: 32 years

Piling exposed: -f 6 to —27 ft: Water side, +6 to -f3±l ft in atmosphere; +3±1 ft to 0 ft (mud line)

in brackish salt water. Soil side, -|-6 to +4 ft in

atmosphere; ground line at -|-4 ft.

Soil characteristics:

-f-4 to —4 ft: Light gray loose silty 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)

pR

7. 8

6. 9

7. 4

Condition oJ files:

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.

-f-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:

-f6 to +4 ft: Uniform thin layer of rust, no

measureable pits.

-t-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 y% in.

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 oj 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
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: Gray to brown coarse sand and river

gravel. —91 to —114: Sand and silty sand underlain by

clay.

Condition oj piles:

Seven full lengths and the interlock edges of 70

piles were inspected. All the pUes were in excellent

condition from the mud line (elevation 0 ft where the

natiu'al soU 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. Sm-faces were uniformily 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 smiace. No measurable pits.

MiU 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 structure

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 of piling: 37 years

Piling exposed: 2.5 ft above ground to 17.5 ft below

the groxmd 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 surroimded by soU.

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 Resistivity

ft -3

Ohm-cm

1, 240

1, 100

4, 900

3. 4

2. 3

5. 9

-10

-16

Condition of piles:

Visual inspection of the pilings revealed that they I 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 1 the laboratory for further examination. ; Practically no mill scale remained on the pile

sm'faces 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 i intact.

j Thin concrete deposits were found on the sm'faces j 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 r over the entire surface exposed directly to the soil

environments. The scale was flakey and easily i removed by scraping. j The following conditions were observed after

{ the piles were cleaned by sandblasting: I + 2.5 to 0 ft: Section exposed to total or partial ' water immersion, or atmosphere. Uniform corrosion

[ of sm-face. Measm-ements of the cross section in ] the top 6 in. of the piles (elevation +2.5 to +2.0) i 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

j on uncorroded smfaces 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, i The original pUe 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. — j 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

f cross section was 28 percent. j —3 to —17.5: In this zone the condition of the

surface was similar to that described above, but was i; less severely corroded. Many isolated pits measmed ' up to 30 mils in depth, and relatively few up to 60 i

10
mils. A maximum reduction in pile cross 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 immediately 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 %-in. 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 pilings at station

60+00 were uncoated.

Date piles driven: November 1953

Date oj inspection: March 1960

Age of 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).

7. 8

7." 6

Condition of 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 sflty clay. Some

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

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).

6. 8

7. 8

7. 5

Condition of piles:

The entire sm'face 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.

1 1
Figure -J. ,1 .l-J'l sfvlion of steel sheet piling exposed below the soil line in a cofferdam structure in the Lumber

River near Boardman, North Carolina.

Exposure, 37 years.

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 % in. at the web, and a thick- ness of K 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.

OB ..«jSI

Figure 5. Steel shed pilimj 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.sectionof coated piling showing 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

ft 93 to 83_..

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 (Shepard Canes)

1,300 (Shepard Canes).

1,700 (Shepard Canes)

2,500 (Shepard Canes) . . .

2,500 (Laboratory)

1,750 (Laboratory)

1,550 (Shepard Canes)

4,000 (Shepard Canes)

850 (Shepard Canes)

1,400 (Shepard Canes)...

7. 4

7. 6

8. 2

12
FiGUBE 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 oj piles:

Approximately 30 to 40 percent of the steel sui-faces 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 thi'ee 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 gi'ay silty sand mixed with

appreciable quantities of cinders, gravel, stones, and

bricks. This horizon appears to be a fill material.

Free water at bottom of trench.

Soil resistivity and pH

Elevation

ft m to 83_,..

m to 73__..

9;^ to 6;^

89 to 84..

88.5

83.5

83

81

83.5 to 80.5

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Ohm-cm

2,800 (4-pin).

9,200 (4-pin).

5,000 (4-pin).

1,300 (4-pin).

3,700 (4-pin).

2,800 (4-pin).

740 (4-pin).

2,000 (4-pin).

1,400 (4-pin).

625 (Sliepard Canes)

.

825 (Shepard Canes)

.

725 (Shepard Canes)

.

910 (Laboratory)

1,700 (Sliepard Canes).

3,900 (Laboratory) -

1,050 (Laboratory)

.

Min

Max

Avg

1,100 (Shepard Canes).

1,400 (Shepard Canes).

1,300 (Shepard Canes).

7. 1

8.

" 6

7. 7

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 dififerent 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 sm-faces were smooth. No

measureable pits were found on the exposed pilings.

Measurements fail to show a perceptible reduction in

wall thiclmess (fig. 6).

c. Sardis Dam Spillway, Sardis, 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 Spillway. 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 of inspection: March 1960

Age of 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: Natm-al soil, reddish brown tight

impervious plastic clay.

13
Soil resistivity and pH 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) _-

5. 7

6. 0

5. 4

Condition of piles:

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

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

piles, 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 mUs in depth, and

three pits between 20 and 28 mUs. 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 SpUlway 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: FUl material consisting of friable

reddish brown clayey sand or sUt 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.

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)

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 imiformly corroded to shallow depths and

contained many scattered pits which generally

ranged in depth between 40 and 90 mUs. 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 soU

particles which appeared to be cemented to the steel

and were difficult to scrape away. Measurements of

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

percent.

UPSTREAM WINGWALL—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 containing many fine roots.

248 to 246 : Mixture of fine rust colored very fine

light yellow silty sand intermingled with pieces of

light gray shale.

Soil resistivity and pH

Elevation

ft 256 to 246-

Resistivity

Min

Max

Avg

Ohm-cm

5,900 (4-pinj.

8,000 (4-pin).

7,000 (4-pin).

pH

14
Soil resistivity and pH—Continued

Elevation

ft 256 to 236

256 to 226

250

248.5

247

246

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

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)

.

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. Six 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. Mill 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 oxide 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 River and Berwick

Bay near Berwick, La. The arch-type sheet steel

pilings had a driving width of 19^ in. and a % in.

wall thickness.

Date piles driven: March 1949

Date of inspection: April 1960

Age of piling: 11.1 years

NORTH END OF LOCK—WEST SIDE

Piling exposed: A 5-ft width 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

t

Water table elevation: —0.5 ft

Soil characteristics:

+ 5 to + 2 ft: Fill material consisting of a mixtxu-e

of gray and brown silty clay containing some gravel

and small shells.

+ 2 to — 1.5: Natural soil consisting of tight bluish

gi'ay impervious plastic clay with patches of tight

brown clay dispersed throughout the profile.

Soil resistivity and pH

Elevation

ft + 5 to -5.

+ 5 to -15

+ 5 to -25

H-4

+ 2

+ 2

+ 1 -1-10

-1.5

Resistivity

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Min

Max

Avg

Ohm-cm

860 (4-pin) .

.

960 (4-pin) . 900 (4-pin) .

990 (4-pin)

.

1, 260 (4-pin)

.

1, 190 (4-pin)

1, 380 (4-pin)

1, 550 (4-pin)

1, 440 (4-pin)

680 (Shepard Canes)

.

950 (Shepard Canes).

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 piles:

+ 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 mils.

The average reduction in wall thiclmess observed on

the three most corroded areas was between 6 and 8

percent.

+ 1.5 to —1.5 ft: Mill scale was intact over about

60 percent of the surface. Slight uniform corrosion

was present on the remaining surface and there were

many pits which did not exceed 25 mils in depth.

There was slight 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 f

t

Water table elevation: + 1 ft Soil characteristics:

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

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

Min

Max

Avg

Ohm-cm

960 (4-pin) _

1, 280 (4-pin) _

1, 130

1, 150_

1, 530_

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 +1 ft: Mill scale was present on 40 percent

of pile s\irfaces. There was uniform corrosion

and pitting where the mill scale was missing. The

three 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 tliick- ness observed in the three most corroded areas was between 8 and 11 percent.

-f 1 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

Histoj'y:

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 ji in. at the web and in. at the

flanges.

Date piles driven: May 1948

Date oj inspection: April 1960

Age oj 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: +5 ft Water table elevation: +2 ft Soil characteristics:

+5 to 3.5 ft: Brown silty clay fill material.

+3.5 to +1: Brown silty clay with pockets o

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 sm'face. 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

measm-ed 40 mils in depth. Nine pits measm-ed

between 22 and 32 mils in depth, and other pits

measui'ed less than 20 mils. The average reduction

in wall thiclcaess measured on the thi-ee 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 wingwall in the Enid

Dam SpUlway. The pUes consisted of interlocldng

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

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

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

Soil resistivity and pTL

Elevation

ft 293

290.5

288

284

282

282.5

Resistivity

OJlTYl-C ITl 8,500 (Shepard Canes) _. 8,000 (Shepard Canes) _

.

10,000 (Shepard Canes)

.

>4,000 (Laboratory).,,

10,200 (Laboratory)

9,500 (Shepard Canes) _ .

5. 1

5. 3

Condition oj 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 soU corrosion conducted

by the National Bureau of Standards have been

restricted to the behavior of metals in disturbed

sods; 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 by the NBS soil investigations as a guide

to estimate the corrosion of metals in all types of

underground installations, 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 previously 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 sods, 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 having 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

amount 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.

Fdl 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 qf soluble salts) , The joH of tlie 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 siraUar 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 tliat engineers make a tliorough

site investigation in designing structures utiUziiig

bmied steel piles in order that du(> allowance may

be made for corrosion and its prevention. The investigation procedm-es he recommended to determine the likelihood of corrosion and its possible

severity are essentially those used to predict corro17
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18
Figure 7. Corrosiveness of soil samples from Bonnet Carre Spillway as indicated bij electrode weight losses after 6 months in modified

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

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

Electrode Loss in weight

A 2.03

1.82

0. 064

0. 15

B

C

D

sion of structui'es, such as pipelines, in disturbed

soils. Emphasis was placed on survey methods

involving measurements of pH, soil electrical resistivity, 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 sm-face were shipped to the National Bureau of Standards. The soils consisted of clay having

a resistivity of 400 ohm-cm and a 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 cell test

in the laboratory [1,16]; by means of this cell the

behavior of iron or steel in difi^erent soils can be

investigated under controlled conditions of moisture

and aeration. In the aerated condition, the moisture

content is controlled to make the soil sufliciently permeable 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 unaerated 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 tlie galvanic current between the electrodes or preferably

by the combined weight losses of the two electrodes.

Good correlations were obtained between the weiglit

losses of corrosion cells set up for six months imdor

aerated conditions using soils from NBS tost sites

and the weight losses occurring in the I'wld at the

test sites on wfought ferrous pipe specimens exposed

for 10 yr [1,16].

The results obtained with the modified Denison

cell on the Bonnet Carre soil samples for six months'

19
exposure in the laboratory under aerated and luiaerated 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 agi*eement 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 relative^ negligible amoimt

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 Ij'ing 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

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

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 relatively small area of the pilings, especially below the

water table zone. Significant pitting was not observed on many of the piles below the water fine.

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

aa appreciable effect on the strength or useful life of pilmg 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 puUed, 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
with a maximum of 4 amp over the 20-hr period.

The absence of highly locahzed corrosion on the

pihngs 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 )^-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 {pH 2.3) and

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

pihng 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

cori'osion of iron or steel and certain soil properties,

such as resistivity, pH 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 structures were obtained on specimens or structures

located in bacldilled soil. The backfilling causes a

drastic disturbance m the oxygen content of the

soil and promotes corrosion of iron and steel by

differential aeration. On the other hand, the

oxvgen 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 mill scale in small areas and localized

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

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 modffied Denison corrosion

ceU 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

pilings indicate that there is not sufficient oxygen

available in undisturbed 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 under 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, di'ainage, soil

resistivity, pH, or chemical composition of soils are

of no importance in determining the cori'osion of

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

behavior of iron and steel under disturbed or backffiled 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 undistm'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 structm-es for periods ranging between

7 and 40 yi" were inspected by pulling piles at 8

locations and maldng 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 pH. 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 sufhciont to significantly affect the strength or useful life of

pilings as load-bearing structures.

Moderate corrosion occurred on several piles

exposed to fill soils which were above the water table

21
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

distiu-bed 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 undisturbed 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 underground. This is contrary to everything

previously published pertaining to the behavior of

steel under distm-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 undisturbed 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 Romanoff, 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 ! (1956).

[3] G. A. Hool and W. S. Kinne, Foundations, Abutments I and Footings, p. 204, 2d Ed., McGraw-Hill Book j 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).

j [5] Louis Beaudry, Quay wall design and construction. Eng.

J. (Canada) U, 394 (1931).

[6] Steel shells in service 39 years still sound and serviceable, t Eng. News-Record 100, No. 15, 590 (Apr. 12, 1928).

{ [7] Life of steel sheet pihng. Iron Age 129, No. 23, 1247

(June 9, 1932).

j [8] B. M. Gallaway, A report on some factors affecting the , life of steel pilings in the Texas Gulf Coast area, Texas Transportation Institute, College Station,

Texas (Oct. 1955). I

[9] G. G. Greulich, Extracted steel H -piles found in good

j 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 I (Dec. 27, 1960). [ [11] M. N. Lipp, Some data on beach protection works. Civil

Eng. 6, No. 5, 291 (1936).

[12] C. W. Ross, Deterioration of steel sheet pile groins at Palm Beach, Fla., Corrosion 5, No. 10, 339 (1949). I

[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 j (Feb. 1952). I [14] Laurits Bjerrum, Norwegian experience with steel pile

| foundations to rock, J. Boston Soc. Civil Eng. 44,

No. 3, 155 (1957).

j [15] B. O. Skipp, Corrosion and site investigation. Corrosion

Technol. 8, No. 9, 269 (Sept. 1961).

[16] W. J. Schwerdtfeger, Laboratory measurement of the ! corrosion of ferrous metals in soils, J. Research NBS i 50, 329 (1953). j

Washington, D.C.

22

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