A UNITED STATES DEPARTMENT OF COMMERCE

PUBLICATION

AlllQD TTDOn A1 1100990019

NBS MONOGRAPH 128

U.S.

DEPARTMENT

OF

COMMERCE

National

Bureau

of

Standards

I oo

no. {^%

Corrosion Rates

On Underground

Steel Test Piles

At Turcot Yard,

Montreal,

Canada -Part 1
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards^ was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety.

The Bureau consists of the Institute for Basic Standards, the Institute for Materials

Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—Linac

Radiation^—Nuclear Radiation-—Applied Radiation^—Quantum Electronics^

Electromagnetics^—Time and Frequency'—Laboratory Astrophysics^—Cryogenics^.

THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies;

and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

Radiation—Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to pro- mote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes

and methods of test; and provides technical advice and services to Government agencies

upon request. The Institute also monitors NBS engineering standards activities and

provides liaison between NBS and national and international engineering standards

bodies. The Institute consists of the following divisions and offices: Engineering Standards Services—Weights and Measures—Invention and

Innovation—Product Evaluation Technology—Building Research—Electronic

Technology—Technical Analysis—Measurement Engineering—Office of Fire Programs.

THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition,

and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center

consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination

and accessibility of scientific information generated within NBS and other agencies of

the Federal Government; promotes the development of the National Standard Reference

Data System and a system of information analysis centers dealing with the broader

aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world,

and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

Publications—Library—Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

" Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.
Corrosion Rates

On Underground Steel Test Piles

At Turcot Yard, Montreal, Canada -Part 1

W. J. Schwerdtfeger and Melvin Romanoff

Metallurgy Division

Institute for Material Research

National Bureau of Standards

Washington, D.C. 20234

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

NATIONAL BUREAU OF STANDARDS, Lawrence M. Kushner, Acfing Direcfor,

Issued July 1972
Library of Congress Catalog Card Number: 72-600112

National Bureau of Standards Monograph 128

Nat. Bur. Stand. (U.S.), Monogr. 128, 17 pages (July 1972) CODEN: NBSMA6

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. 013.44:128). Price 30 cents. Stock Number 0303-1015
Contents

Pase

1. Introduction 1

2. Description of the test sites 1

3. Corrosion rates based on polarization measurements 3

3.1. Measurement techniques 3

3.2. Results on test piles at sites A, B, and C 5

3.3. Corrosion rate of composite piling under

pier A-10 near site B 6

4. Physical inspection of extracted piling 8

4.1. Site A, driven pile No. 5 8

4.2. Site B, driven pile No. 1 9

4.3. Site B, horizontally buried pile No. 7 9

4.4. Site C, driven pile No. 1 9

5. Analysis of the data 10

6. References 12

Corrosion Rates on Underground Steel Test Piles

at Turcot Yard, Montreal, Canada—Part I W. J. Schwerdtfeger and Melvin Romanoff*

In 1966, isolated steel H-piles allocated for underground corrosion tests were installed in three locations at the Turcot Yard Interchange of the Transcanadian Highway at Montreal. The

reason for the installation was to furnish answers to some questions concerning the corrosion

characteristics of piles, 12 in-74 lb/ft(30.5 cm-110 kg/m), which are identical with the piles supporting the concrete piers under the highway. Polarization measurements have been made

once every year since installation. This paper describes the determination of corrosion rates based on the polarization measure- ments made up to the time of removal of the first group of piles in 1969. The piles, placed

underground at three locations, difler mainly in that at one site all the piles are bare, at the second site the upper ends of the piles are coated with an epoxy paint and at the third site the upper ends are encased in concrete. Physical measurements made on the cleaned piles after removal are correlated with corrosion rates calculated from the polarization measurements. Also, penetration rates on the piling based on the polarization data are compared with average penetration rates (based on actual weight losses) on relatively small pipe specimens. The pipe speci- mens were removed from 28 underground sites having a range of soil resistivities comparable

to those of the three piling sites. Using one of the polarization techniques applied to the individual test piles, polarization measurements were also carried out on 32 interconnected piles supporting one of the concrete

piers. The calculated average corrosion rate of the 32 piles was found to compare favorably with

that of the separate test piles in the same area. Key words: Average penetration rate; H-piles; instantaneous corrosion rate; linear polarization;

pit depth; polarization curve.

* Deceased

1 . Introduction

Several thousand 12-in, 74 lb/ft (30.5 cm, 110

kg/m) steel H-piles of German fabrication were driven

to bedrock during the construction of the Transcanadian Highway at the Turcot Yard Interchange, Montreal 1966. Because of the corrosive nature of some of

the fill (soil and cinders) used at Turcot Yard, some

engineers were of the opinion that cathodic protection

should be used on the underground piling supporting

the massive concrete piers under the highway. However, in view of a paper by Romanoff [1]^ published by

the National Bureau of Standards (NBS) in 1962,

a difference of opinion prevailed regarding the necessity for cathodic protection. Accordingly, during construction of the highway, steps were taken to provide

access for cathodic protection by interconnecting the

piles constituting a concrete pier, should protection

be deemed advisable pending further investigation. In the meantime, a cooperative project was undertaken

by NBS and National Boring and Sounding, Inc. Montreal (responsible for the underground structures)

.

The project was sponsored by the Province of Quebec

and the American Iron and Steel Institute (AISI).

It was agreed that NBS would design a test program

and that National Boring and Sounding, Inc. would

install piles and remove some of them after 3,6,12,25

and 50 years of exposure for inspection and physical measurements. Three sites were selected in the Turcot

Yard area where piles, identical to those used to sup- port the concrete piers, were driven to bedrock. At

one of the sites the piles were left unprotected (bare),

at the second site the upper part of the piling exposed

to the fill soil was protected with an organic coating

and at the third site concrete covered the upper end.

It was decided to make yearly polarization measure- ments over a period of several years in order to cal- culate average rates of corrosion on the bare surfaces

of the piling and then to compare the calculated data

with physical measurements made on removed piles

following removal of corrosion products. The first piles were removed from each of the three sites in 1969 after 3 years of exposure and the intervening

measurements and results are described in this paper. This project fits nicely into the overall NBS pro- gram on piling corrosion sponsored by the AISI. It

is the first major attempt to evaluate the significance of instantaneous corrosion rates measured by polarization techniques on underground piling in situ.

2. Description of the Test Sites

Seven test piles were installed during September

1966 at each of the three sites, designated as A, B, and C, located in the Turcot Yard area, Montreal

during the construction of the Transcanadian highway

interchange. The piles^ were steel H-piles, 12 in x

12 in x 74 lb/ft (30.5 cm x 30.5 cm x 110 kg/m).

' Figures in brackets indicate the literature reference at the end of this paper.

2 Chemical composition, weight percent—C, 0.11-.14 ; Mn, 0.52-.63 ; P,

0.054-.067; S, 0.026 .038; Si. 0.04-.08.
the same size and from the same source as the H-piles

driven to support the piers of the highway.

At each site, six piles were driven to bedrock,

approximately 30 ft (9.2 m), one of the six being in the center of a circle of piles having a radius of about

6 ft (1.8 m). Five of the driven piles were equally

spaced on the circumference of the circle. The seventh

pile was buried horizontally, 10 ft (3.1 m) outside

and tangentially to the circle of driven piles, in a

back-filled trench previously excavated to a depth of about 7 ft (2.1 m). The upper 7 ft (2.1 m) of the driven piles were also exposed to back-filled soil. The

excavated depth of 7 ft (2.1 m) corresponds to the depth of the concrete footings enclosing the upper

ends of the steel piles under the piers of the actual highway structure. The horizontal pile was included

at each site for the purpose of comparing the pattern

of corrosion on the steel surface exposed to disturbed

soil and fill (previously excavated) with the corro- sion on the surface exposed to undisturbed soil (natural soil). The driven piles, of course, were exposed

to undisturbed soil below the excavated areas. The piles at the three sites were arranged in the same way with the following exceptions. At site C, concrete encasements were poured over the upper 7 ft (2.1 m) of the six driven piles and over one end of

the horizontal pile, again for a distance of about 7 ft (2.1 m). The concrete encasement was rectangular

in cross section with at least 6 in (15.2 cm) of concrete covering the steel at all points. All piles at site A were exposed entirely bare. At site B, an organic

coating was used on the upper ends of the piles to cover about the same area of steel encased by concrete at site C. Before applying the coating, the area

to be coated was cleaned with a motor-driven rotary

steel wire brush. The brushing operation was immediately followed by applying a hand-brushed coat of epoxy primer. The next day, a brush coat of C-200

coal-tar epoxy coating was applied over the primer

coat. After driving the piles and before the concreteing

and coating operations just described, the driven piles were cutoff at the top ends 2 ft (0.61 m) below the ground line. Identification numbers were welded on

each pile about 12 in (0.3 m) below the top. Prior

to driving, identification numbers were also welded

about 24 in (0.6 m) from the bottom ends. A 1.375 in (3.5 cm) steel reinforcing rod was welded to the top

of each driven pile and terminated about 12 in (0.3 m)

below the ground line. On the horizontal piles, rein- forcing rods were also positioned vertically and welded

to the center of the pile. The rods served as points

of electrical contact for carrying out the polarization

Figure 1. Site C—View (before backfilling) showing the 6

driven piles encased by concrete at the upper ends.

Reinforcing rods shown protruding above the concrete are for the electrical connection.

measurements. To keep the soil out of direct contact with the rods when not in use, the rods were covered

with removable molded concrete caps which pro- truded above the ground line. Figure 1 shows the concrete encased piles (upper ends) at site C before

back-filling and figures 2 and 3 are views after backfilling.

Figure 2. Site C—View (after backfilling) showing concrete caps covering the reinforcing rods.

Location of the horizontal pile is indicated by arrow in the background.

Tables 1 and 2 show soil types at sites A and B,

respectively, and also soil resistivity and pH as measured in July 1966. The resistivities of excavated soil areas were measured in situ with Shepard canes [2].

At depths of 8 ft (2.4 m) and deeper, soil samples were shipped to the NBS laboratory in sealed nonmetallic containers. Resistivities were measured in the laboratory using a standard soil cup and a Wheatstone

bridge. Resistivities are corrected to 60° F. All pH

measurements were from soil samples in sealed containers. Table 3 shows mainly a chemical analyses

of soil samples from all three sites made by a Canadian

laboratory in accordance with NBS Circular 579,

table 6 [2].

2
Figure 3. Site C—Showing surrounding highway structures.

Table 1. Soil characteristics based on soil borings at site A

Turcot Yard, Montreal, Canada

ple Depth ft Soil types

Resistohm-cm

at 60° F

pH

A 3 - 4.5 Fill—sand, brown silt cinders. 2030 7.8

B 5 - 6.5 Fill —brown silt, black

shale, trace of clay. 2130 7.6

6 .5- 8 Boulder.

C 8 - 9.5 Black shale, gravel, sand.

D 9 . 5-10 Peat. 1170 7.0

10 -10.5 Peat.

E 10.5-11.5 Marie. 1630 7.4

F 11.5-13 Marie. 1880 7.3

G 13 -13.9 Gray Clay. 1470 7.2

13.9-14.5 Sand, silt, gravel.

H 15 -15.9 Sand, silt, gravel. 4570 8.2

15.9 Boulder obstruction.

3. Corrosion Rates Based on Polarization

Measurements

3.1. Measurement Techniques

The polarization techniques used for measuring in- stantaneous rates of corrosion on the piling under

Table 2. Soil characteristics based on soil borings at site B

Turcot Yard, Montreal, Canada

Sample Depth, ft Soil types

Resistivity, ohm-cm

at 60° F

pH

A 0L — .5.0 Fill—cinders, clinkers. 510 7.2

B 3 5- 5 Fill—cinders, clinkers,

silt, gravel, trace of brown sand.

400 7.2

C 5 - 6.5 Fill—cinders, sand,

gravel, trace of clay.

1020 7.5

D 7 - 8.5 Fill —cinders, sand,

silt, gravel.

1220 6.9

E 8 5-10 Peat.

F 10 -11.5 Peat.

11 5-12 Marie. 460 6.8

G 12 -13.5 Marie. 660 7.3

H 1 0 13 0-14 .

0

Gray clay. 1120 7.1

14 5-15 Silt, sand, gravel to boulders.

K 15 -16.5 Silt, sand, gravel to boulders.

4570 7.8

16. 5-18 Gravel.

18 -20 Silt, gray sand.

L 20 -21.5 Silt, gray sand. 4830 7.7

22 Silt.

discussion are based for the most part on a considerable amount of earlier laboratory and field work on

relatively small specimens [3,4,5,6]. Weight losses calculated from these earlier polarization measure- ments have shown by comparison with actual weight

losses on the same specimens that agreement is remarkably good. Reference [6] also describes polarization

measurements made on underground piling and al- though, in the case of the piling, weight loss verifica- tion was not possible, the corrosion rates as measured

by the polarization method seemed very reasonable,

especially so upon inspection of and pit depth measurements on one of the piles after extraction from

the soil.

a
4) O

Lou

+ Z

^ CO IM cr:roc^roir5-*r-H(NOOO

oococo^-a^foo^o

1—li—ICOCOOC^'—IC^ oooooooo OOOOOf-COl—lOOOO oooooooo

•'J'cOOOONrtCMCO -imcooovo^iM

CO CO O O OrH,—lOOOcO^CMOO-—

I

OCOrt^C<ION'*'^CO>000 r-HnH(>ICOOOCOONCOr—tOCSI

!N (N O O t— in o o o o o OMCOOOOOO

o o o o o

CO <M <M CO lO oooooooooooo o o o o o o

On C^ O VO ^'3'rfO\0\Or-(T# OCOOOlOCncOI:^

LO CO CO 'J' M '*'^CO<N'rf'COCOCO(MO 'S' ^ CO iM irq CO M

a

cc; o

in o t-^ ino O ooCS! CM Csl

cu a. s s ooo „ ^oovniniOLno Oinin c cOint^f-i:— r~in LOinco D'*^>Ovocococo (MiMCM---- ^^voininco

OOOOOOOO inoinininoinin r-Mininmr-int— r-lr-(C\lLnin(N<N^

3 3 E

J3 csiinoM'^'S'coco t^r-inoNr—ivocoiOi—icooco

t^i^-r-insovot^t^eot— cor~- iM^COvOr—iOOnOnint--t--t--oocot^t--

CO o CO CO in NO in o in CO O * O ON t-- o CO in c--ir-incocO'*cMC\iONCOso^D

On in rJ5

On O O O O in CM o o o o

coco.—1<*0000 coTfininoooo o in in O CO "* o o —1 ^ CO I in O O CO CO CO On

EEEEEEEE E E E E

CU P-i Q-i CLi Oh E E E E E E E EP-< Oh D-i P-i Ph Pi E E E E E E

05

CO CO

J3H

4
Two polarization techniques were used in making

measurements on the piling discussed in this paper. A preliminary measurement, polarization rate ( AV/

AI), more commonly known as the polarization

resistance or linear polarization method, based to a large extent on experience, was used in order to esti- mate the magnitude of the current increments applied

in determining the polarization curves. Corrosion

rates were calculated primarily from changes-in-slope,

known as breaks [4], in the cathodic and anodic

polarization curves. Corrosion currents were also cal- culated from the AV/AI data by a method described

elsewhere [4].

The use of a bridge circuit for the elimination of IR (voltage drop through the soil) is invariably a necessity when making polarization measurements in

soils without interrupting the polarizing current, unless the IR is an insignificant part of the measured

potential change. Here the Holler bridge circuit [7] was used. Such a bridge circuit designed chiefly for measurements on piling has already been described

[6]. As a word of caution, it should be mentioned

that the arm of the bridge used for balancing out the IR requires variable resistors capable of carrying the polarizing current. However, the physical size of these

resistors does not present a problem. For the piles in Montreal, the value of the total balancing resistance was less than 2 CI. Voltage loss across the balancing

resistors is not prohibitive because the value of re- sistance required is an inverse function of the area

of metal in contact with the soil. It was found that two 12 V storage batteries connected in series pro- vided ample current for the polarization measurements. Electrical apparatus used in Montreal is shown

at one of the test sites (fig. 4).

Figure 4. Electrical apparatus as set up for polarization measurements.

T

1 1 1 I \ r

-7 I I I I I I

I \

\ \ L

(5

' 0 .1 .2 .3 .4 .5 .6 .7 -8 .9

.01 .03 .06 .1 .3 .6 I 3 APPLIED CURRENT, A

Figure 5. Cathodic and anodic polarization curves obtained on H-pile No. 1, site B, after exposure for 34 months.

A and B are the same data plotted respectively on rectangular and semi- logarithmic coordinates.

3.2. Results on Test Piles at Sites A, B, and C

A set of polarization curves obtained on pile 1,

site B just prior to extracting the pile for inspection

is shown in figure 5. These curves are typical of all obtained on the several piles, except for the actual and relative values of Ip and Iq which indicate the values of polarizing current at which breaks in the curves occur. In calculating corrosion rates, it was

assumed that corrosion occurred only on bare steel surfaces exposed to the soil and fill. Thus, at sites B

and C the area considered in calculations excludes

that respectively under the organic coating and under

the concrete. Therefore, at site B, where upon inspection corrosion was found under the coating, the cor- rosion rates after 3 years of exposure were actually

less than those stated later in the tables. This is so because the polarization measurements reflect the total corrosion including that in areas where the coating

had deteriorated. The bare areas originally measured

for the purpose of making calculations, later small

deviations notwithstanding, are tabulated in table 4. Instantaneous corrosion current densities, based on

these areas and calculated from measurements made

at approximately yearly intervals are tabulated in table 5. A remote copper-copper sulfate reference

electrode was used in making the measurements shown

5
in table 5. The reference electrode was positioned in a moist location on the soil surface about 50 ft (15.2 m)

away from the pile under observation. All polarization data were obtained by applying approximately

equal increments of continuous current for one minute

intervals and then reading the pile potential at the end of each interval. Usually, cathodic polarization curves were obtained first and followed the next day

by the anodic curve. In the field, polarization data were immediately plotted on rectangular coordinates

in order to verify the occurence of a break in the

curve, before commencing measurements on the next

pile.

Table 4. Area of uncoated steel exposed to soil and fill at the

test sites

Pile No. Area of bare surface, ft ^

Site A Site B Site C

1 157 > 149 1 141 2 130 125 150

3 131 145 155 -,4 /-„ 133 145 152 5 1 142 140 148 6 131 149 149

7 152 2 149 161

NOTE: Area is equal to approximately 6.1 ft ^ per linear ft of H pile 12 BP (12 in.Xl2 in.), 74 lb/ft.

' Pulled July 1969.

^ Horizontal pile—removed July 1969.

Average penetration rates of metal on all bare

surfaces exposed to the soil or fill as calculated from

yearly instantaneous corrosion currents (based on

semilog curves, table 5), are shown in table 6. Values

are rounded to the nearest decimal place. Where values

are missing, no attempt was made to obtain data.

3.3. Corrosion Rate of Composite Piling

Under Pier A-10 Near Site B

During July 1969 an attempt was made to measure

the instantaneous corrosion rate of the interconnected

piling under pier A-10 indicated by arrow in figure

6. One of the underground test piles at the site in the foreground of the photograph, about 100 ft (30.5

m) away from the pier, was used as an auxiliary

electrode for passing current through the soil to the composite piling under the pier. Because of the limited current carrying capacity of resistors in the bridge

circuit, the corrosion rate measuring technique was

confined to the AV/AI method. The composite piling

under pier A-10 consists of 32 piles of about the

same size as the test piles and each pile presumably

having about the same bare area exposed to the soil down to bedrock. With the bridge balanced and cur- rent applied cathodically, the average corrosion current per pile was calculated to be 121 mA. After re- moving the polarizing current and waiting some time

for reasonable stabilization of the piling potential, current was applied so as to make the piling anodic.

The average corrosion current under these conditions was now calculated to be 102 mA per pile. The aver- age area of bare piling for those with upper portions

encased in concrete is about 149 ft^ (13.9 m^) based on table 4. By averaging the corrosion currents cal- culated from cathodic and anodic polarization curves and using an area of 149 ft^ (13.9 m^), the corrosion

of the piling under pier A-10, based on current density, is calculated to be around 0.75 mA/ft2(81juA/

dm^). This compares reasonably with the corrosion

data calculated for the test piles (table 5). The cor- rosion rate (surface penetration) based on this current density is equivalent to about 0.38 mpy (10 /im per year). This is comparable with the penetration

rates calculated for the test piles (table 6)

.

4. Physical Inspection of Extracted

Piling

Before exposing test piles to the underground en- vironment, random flange thickness measurements

were made at about 12 in (30.5 cm) intervals along

the entire length of each pile on two of the flanges. After 3 years of exposure, one driven pile was ex- tracted from each of the 3 sites and the horizontal

pile (buried in a backfilled trench) was removed from

site B. Soil was scraped from the piles and rotary

motor-driven wire brushes were used to remove loose

mill scale and corrosion products. Random flange

thickness measurements were repeated on the same

flanges as done before exposure. In addition, pit

depths were measured where corrosion was signifi- cant. Photographs showing mechanical equipment and

the driven pile at site C in the process of being ex- tracted are illustrated in figures 7, 8, and 9.

4.1. Site A, Driven Pile No. 5

No significant differences were observed between

the original and final random flange thickness measurements. Approximately 23 ft (7 m) of bare pile

had been exposed to the soil together with a steel plate, 8.5 in x 8.5 in (21.6 cm x 21.6 cm), welded to an outside flange about 15 ft (4.6 m) from the bottom

of the pile. No significant amount of corrosion was 6
3 <\ o ^

rf Tj< oo O O O

O CO C-1 vO On ^ O ^ O O03 On 00 lO O t-- O O O O O O

O

X

ONNO

ON

a T3 O 00 CO CO

i-H o o o o o

U-S LO o ^

CO ^ O LO NO -O O .—1 o o o

CNJ CNl lO 00 o o o

m CO CO CO CM CO .—I f-H

On NO i—I CO d o o i-H o o

r~- CO On I NO CNJ O ^ O r—1 O CNl

CO NO NO NO NO o o o o o o

CO

NO

On

<

-a

6D c OO On On O O O O O ,—I r-H

CNJ CNl

CNl .-H o

E V

On CO On O O

ON NO o o

O (M

> CO^CN] jLOCO CO^"*

c .5

CO -O O LO ^ o

r-H O

CO r-H

CMCNl.—(|COI> Mt—,—1| |ON CO| |CO|CO

CNicorfi/jr- ^McO'S'LOr^ ^cmco'^loi^

7
Table 6. Average penetration rates on piling surfaces (test piles) caused by corrosion calculated from polarization curves

rue

Ly 0 .

Average penetration rate, mpy '

1967

After 10 Mo.

exposure

1968

After 22 Mo.

exposure

1969

After 34 Mo.

exposure

A 1 0.6 0.4 0.5

2 0.6 0.6 0.6

3 0.5 0.4 0.6

4 — 0.3

5 0.6 II I 2 0.4

7 0 3 0 3

B 1 0.6 0.5 2 0.6

2 0.8 0.6 0.7

3 0.5 0.7 0.6

4 — — 0.6

5 0.5

7 1.4 0.9 '0.7

C 1 0.6 0.7 2 0.6

2 0.6

3 0.6

4 0.6 0.5 0.5

5 0.5

7 0.6 0.4 0.5

' Average penetration is based on corrosion by Faraday's law, when 1 mA/ft ^ is equivalent to a metallic weight loss of 2.7 mdd (milligrams per sq dm per day) and mpy (mils or thou- sandths of an inch per year) = mdd XO. 183. 1 mil = 0.001 inch = 25 micrometers (jum).

2 Pulled July 1969.

' Horizontally buried—Removed July 1969.

Figure 6. Site B—arrow points to highway pier A-10 where

instantaneous corrosion rate was measured on the composite

underground piling supporting the pier.

Figure 7. Site C—Rigging used to extract piling. View shows pile CI with concrete broken away for linkage connection to the crane cable. Welded reinforcing rod is also visible.

Figure 8. Site C—pile CI in the process of being extracted. 8
Figure 9. Site C—pile CI after extraction.

observed from the bottom of the pile up to 17 ft (5.2

m), including the welded area. About 80 percent of

the mill scale was still intact. On the remaining upper 6 ft (1.8 m), which had

been exposed almost wholly to excavated soil and

fill, the mill scale had almost entirely disappeared.

One outer flange area had a few pits 35 to 40 mils

(0.87 to 1.0 mm) deep and many scattered pits 20

to 25 mils (0.50 to 0.62 mm) deep on the upper 3 ft (0.9 m) end of the pile. The other flange showed

minor surface attack with little or no significant pitting. The web and inner flange areas on the upper

6 ft (1.8 m) had a calcareous deposit in evidence

near the top and some pitting up to 25 mils (0.62 mm)

in depth where there was no deposit.

4.2. Site B, Driven Pile No. 1

The differences in measurements of flange thickness

made at random before and after exposure were in- significant. This pile also had a plate, similar to the

plate previously mentioned, welded to the outside of one of the flanges about 13 ft (4 m) from the bottom

end of the pile. The welds appeared unaffected by

corrosion.

The entire pile, including the coated area at the upper end, was about 28 ft-4 in (8.6 m) long. The

lower 10 ft (3 m) was rusted but showed no pitting

beyond the depth of the mill scale, about 50 percent

of which was still intact. Between 10 ft (3 m) and 21

ft (6.4 m) from the bottom, the flange areas had

several pits up to 30 mils (0.8 mm) and scattered pits

40 to 90 mils (1 to 2.2 mm) in depth. The web area

in this range had about 60 percent of the mill scale

intact with some calcareous deposition and scattered

pitting to a depth of 65 mils (1.6mm).

The area in the range 21 to 24 ft (6.4 to 7.3 m)

from the bottom had the most corrosion. This is the area immediately below the coated upper area of the

pile. There were several pits ranging from 60 to 100

mils (1.5 to 2.5 mm) deep on the outside of the

flanges. The edges of the flanges were most noticeably

affected by corrosion. On the inside flange and web

areas most of the pits were less than 25 mils fO.62 mm) deep.

The coated area (upper end) of the pile started at 24 ft (7.3 m) from the bottom. This coated area and

the bare area in the range 21 to 24 ft (6.4 to 7.3 m)

had been exposed to backfilled soil. On the flanges

(inside and outside), the coating was about 50 per- cent removed. There were many pits between 30 and

60 mils (0.75 to 1.5 mm) in depth. The coated web

area was less affected by corrosion than were the

flange areas, with most of the coating still intact.

4.3 Site B, Horizontally Buried Pile No. 7

Differences in random measurements of flange

thickness before and after exposure were insignificant.

This pile was 31.5 ft (9.6 m) long of which 5.3 ft (1.6 m) at one end was coated. The most noticeable

corrosion was on the edges of the flanges along the

entire length of the pile. The coating was blistered and peeled off readily. There were many pits in the coated area on the outside of the flanges ranging in depth between 50 and 85 mils (1.3 to 2.1 mm). The

entire flange area on the outside was attacked and

the mill scale was almost all gone. There were numerous pits in the uncoated area ranging from 20 to 40

mils (0.5 ,to 1 mm) in depth. Some pits were 100

mils (2.5 mm) deep.

The web and inside flange areas had fairly uniform

corrosion with numerous pits between 20 and 30

mils (0.5 and 0.75 mm) in depth and a few 45 mils

(1.1 mm) deep.

4.4. Site C, Driven Pile No. 1

This pile was 31 ft (9.5 m) long including the upper

end encased in concrete for 4.5 ft (1.4 m). In addition

to the use of a motor-driven rotary wire brush for cleaning, an air gun and chisel were used to remove

the concrete. Random measurements of flange thick- ness made before and after exposure revealed no

9
Figure 10. View of pile CI after extraction and wire brushing,

showing the welded plate and surrounding area of the pile.

significant differences, except perhaps in the bare

area immediately outside of the concrete encasement. The mill scale from the bottom of the pile up to 20 ft (6.1 m) was about 75 percent intact and the

little corrosion which occurred was in the form of shallow pitting through the mill scale. The weld at 20 ft (6.1 m) from the bottom and around a steel plate (fig. 10) was unaffected by corrosion. In the area 20 to 24 ft (6.1 to 7.3 m) from the bottom, about

60 percent of the mill scale was gone from the out- side of the flanges with some pits up to 25 mils

(0.62 mm) deep.

In the area 24 to 26.5 ft (7.3 to 8.1 m) from the bottom, just below where the concrete had been during exposure, corrosion was quite uniform on the outside of the flanges. The average difference in flange thickness based on about 75 measurements

made with a micrometer calipers in this area and 75

measurements made in the area previously encased

in concrete was about 9 mils (0.23 mm). This 2.5 ft (0.76 m) section of pile is where uniform corrosion was the most noticeable. Some pits in this area were from 30 to 65 mils (0.75 to 1.6 mm) in depth but

most of the pits were less than 20 mils (0.5 mm) deep.

Corrosion on the inside of the flanges and on the web was in the form of pitting where the mill scale (most of which was still intact) was removed. These

pits were no deeper than the thickness of the scale, 10 to 20 mils (0.25 to 0.5 mm).

The upper end of the pile which had been encased

in concrete was unaffected by corrosion.

5. Analysis of the Data

Having presented corrosion rates based on polari- zation measurements and corrosion data obtained on

extracted piles based on physical measurements, a

comparison of the two types of measurements is in order. The corrosion on this piling might also be

compared with the corrosion observed on piling ex- posed elsewhere and also with the corrosion measured

on steel pipe specimens exposed to a variety of soil environments having resistivities of the same order of magnitude as that of the piling soil environments. It must be borne in mind that excessive pitting on underground pipelines cannot be tolerated whereas on piling the important factor pertaining to corrosion is its effect on the load bearing capability of the underground structure. The average penetration rate on all of the piles

(table 6) based on the three sets of polarization meas- urements made over a period of two years was between

0.5 and 0.6 mils (12 and 15 fjm) per year on all bare

surfaces exposed to the soil. Thus, it ought not be

surprising that the random measurements of flange

thickness made before and after 3 years of exposure

indicated no significant difference. At site A, most of the corrosion observed by physical inspection after 3 years of exposure took place on

the upper end of the extracted pile. This corrosion

pattern was also indicated by polarization measure- ments made on pile No. 1, site A, after 2 years of exposure in 1968. A boring rig was used to drill a hole about 12 in (30.5 cm) to the side of the pile

down to its very bottom. As the drill was lowered, a Cu-CuSo4 reference electrode was alternately placed

into the hole at depths of 5,10,15,20 and 22 ft (1.5,3,4.6,6.1 and 6.7 m) below the surface. Based on

the AI/AV method used for measuring corrosion

current, the corrosion current densities (based on the

area, table 4) at the respective depths were calculated

to be 1.7, 1.2, 1.4, 0.7 and 0.4 mA/ft^ (183,129,150,

75 and 43 /xA/dm' ) . The current densities in table 5

represent an average because the reference electrode was placed in a remote position. Similar measurements

made on the same pile with the reference electrode positioned on the earth's surface, showed that the cor- rosion current was higher when the electrode was close

to the pile than when placed at a remote location. The boring rig was also set up at site B at one pile in the same manner as described for site A except that only corrosion potentials of the pile were read as the reference electrode was alternately placed into the

hole. It was observed that the corrosion potentials of the pile varied by as much as 200 mV, the more

anodic potentials being at the middle and lower areas

of the pile. The more anodic values were attributable

to the probably lower concentration of oxygen avail- able in these areas.

10
The polarization measurements reveal that the greatest amount of metal loss occurred on horizontal pile No. 7, site B as is shown by the relative magnitude of

the corrosion currents (table 5) . This was later verified by the corrosion observed upon examining the pile after three years of exposure and by pit depths and

their frequency of occurrence. This particular pile was

unique in the value of its corrosion potential. From

the time that the first polarization measurements were made, one year after exposure, the corrosion potentials of pile No. 7 were always positive with respect to the Cu-CuSo4 electrode, ranging from 0.128 V in 1967

to 0.234 V in 1969 when the pile was removed. The

reason for the positive potentials could not be attrib- uted to stray currents in the area because the driven

test piles at the same site and piling under a nearby

pier footing exhibited normal negative potentials. After some inquiry among persons involved at the time the piles were installed, it was learned that this particular pile was inadvertently completely covered

with the primer coat in preparation for application

of the coal tar epoxy coating. When it was realized

that the coating was to be applied only on one end of

the pile, similar to that on the driven piles at the same

site, a solvent was used to remove the primer from the area that was supposed to have been left uncoated.

Thus, the positive potentials are attributed to the

effect of the chemicals.

Based on the instantaneous corrosion rate measurements, the maximum average rate of penetration (table

6), after 34 months of exposure is 0.7 mils/yr. (18

;um/yr). Over a period of 50 years, this rate would

account for a reduction in metal thickness of 0.07 in. (1.8 mm) or about 12 percent of the H-pile thickness

based on a metal thickness of 0.6 in. (15 mm). At

site C, physical measurements made on pile No. 1 revealed a reduction in flange thickness of 9 mils (0.23

mm) over a period of 34 months in the most corroded

area, from 0 to 2.5 ft. (0 to 0.78 m) below the concrete encasement. This would account for a reduction in metal thickness of 0.150 in. (3.8 mm) in 50 years, or 25 percent of the metal thickness assuming that corro- sion continued at the same undiminished rate. The

Corps of Engineers [5] mentioned a 35 percent loss in cross section as an acceptable maximum over a period of 50 years. While protecting the metal which it covers, concrete does setup a galvanic cell comprising the underlying

metal and the metallic area adjacent exposed directly

to the soil. The thicker the cover of concrete and the higher the resistivity of concrete becomes with aging

the less potent the galvanic effect becomes. On the

other hand, a good protective coating in place of the concrete would, theoretically at least, eliminate this galvanic effect. Adverse conclusions should not be

reached about coatings because of the relative ineffec- tiveness of the epoxy coating used at site B. It could

be that the coating was not applied in the most effec- tive manner. Assuming no serious loss of bond

strength, the use of concrete over a coating at the upper ends of the piles would minimize the galvanic

effect caused by bare metal adjacent to the concrete. One might ask how the corrosion rates based on

these few polarization measurements compare with

corrosion rates of plain ferrous pipe specimens. Based

on actual weight loss-time curves involving hundreds

of 1.5 in X 12 in (3.8 cm x 30.5 cm) pipe specimens,

the corrosion current densities, after five years of exposure in 28 sites having soil resistivities between

500 and 3000 O-cm (similar to sites A, B, and C),

averaged 1.6 mA/ft- (172 /xA/dm^) and ranged be- tween 0.12 and 6.2 mA/W (13 and 666 //.A/dm^) [8].

This average corrosion current density of 1.6 mA/ft^

(172 /u,A/dm") on the pipe specimens, even after 5

years of exposure, is higher than the average corro- sion current density of the piling (table 5) after only

34 months of exposure. In soils, there is a general

tendency for the corrosion rate of iron or steel to lessen with time and usually to level off after 5 years. Aver- age corrosion current densities as high as 6.2 mA/ft^

666 /xA/dm^) are rather unlikely on underground

piling, even in low resistivity soils. The corrosion rates and patterns observed on the H-piles described in this paper are similar to what

was found on pipe piling exposed to a corrosive underground environment elsewhere [6]. On an extracted pipe pile it was found that most of the corrosion, in terms of depth and number of pits, occurred at the upper end of the pile regardless of the fact that the

soil at the upper end had the higher resistivity.

The periodic polarization measurements and extraction of these piles for inspection at the three sites will continue and the results will be published periodically.

The financial support of the American Iron and

Steel Institute is gratefully appreciated and thanks go

to the Province of Quebec, Canada for providing the

test sites and for supplying and installing the test piles.

The continuing cooperation cheerfully provided by

Messrs. Marcel Dufour and Roland Chevalier of National Boring and Sounding, Inc., Montreal, Canada,

required in carrying out electrical measurements and

piling inspections, is greatly appreciated.

11
6. Reference

[1] RomanofF, Melvin, Corrosion of steel piling in soils, Nat.

Bur. Stand. (U.S.), Monogr. 58, 24 pages (Oct. 1962) —

Superseded by Schwerdtfeger, W. J., and Romanoff, M., NBS Papers on Underground corrosion of steel pilings (1962-1971), Nat. Bur. Stand. (U.S.), Monogr. 127, 63

pages (Mar. 1972) which includes Monogr. 58. [2] Romanoff, Melvin, Underground corrosion, Nat. Bur. Stand.

(U.S.), Circ. 579 (Apr. 1957).

[3] 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).

[4] Schwerdtfeger, W. J., Corrosion rates of metals, alloys and galvanic couples as measured by polarization techniques. Materials Research and Standards, ASTM 10, 22, (Mar. 1970).

[5] Corps of Engineers-Lower Mississippi VaUey Division, Vicksburg, Miss., "Report on corrosion of underground

steel piling," December 1969.

[6] Schwerdtfeger, W. J., Polarization measurements as re- lated to corrosion of underground steel piling, J. Res. Nat.

Bur. Stand. (U.S.), 75C (Eng. and Instr.), No. 2, 107-

121 (Apr.-June 1971).

[7] Schwerdtfeger, W. J., Current and potential relations for the cathodic protection of steel in a high resistivity en- vironment, J. Res. Nat. Bur. Stand. (U.S.), 63C, (Eng. and Instr.), No. 1, 37-15 (July-Sept. 1959).

[8] 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).

12

•i!r U.S. Government Printing Office: 1972 0—466-932
FORM NBS-1I4A (t.7i) U.S. DEPT. OF COMM. 1 . PU B LIC AT ION OR RE PORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA NBS-MN-128 SH E E T

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Corrosion Rates on Underground Steei Test Plies

at Turcot Yard, Montreal, Canada-Part I

5. Publication Date July 1972

6. Performing Organization Code

7. AUTHOR(S) >:< Wo J. Schwerdtfeger and Melvin Romanoff

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS

MATIOMAT RIIRFAII OPT t^TAMnARHQ

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, No Y.

10017

Province of Quebec, Canada

13. Type of Report & Period Covered Interim

14. Sponsoring Agency Code

15, SUPPLEMENTARY NOTES

* Deceased

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.) In 1966, isolated steel H-piles allocated for underground corrosion tests were installed in three locations at the Turcot Yard Interchange of the Transcanadian Highway

at Montreal. The reason for the installation was to furnish answers to some questions

concerning the corrosion characteristics of piles, 12 in-74 lb/ft(30,5 cm-110 kg/m), whi ;h

are identical with the piles supporting the concrete piers under the highway. Polarization

measurements have been made once every year since installation.

This paper describes the determination of corrosion rates based on the polarization

measurements made up to the time of removal of the first group of piles in 1969. The

piles, placed underground at the three locations, differ mainly in that at one site all the

piles are bare, at the second site the upper ends of the piles are coated with an epoxy

paint and at the third site the upper ends are encased in concrete. Physical measurements made on the cleaned piles after removal are correlated with corrosion rates calculated from the polarization measurements. Also, penetration rates on the piling based

on the polarization data are compared with average penetration rates (based on actual

weight losses) on relatively small pipe specimens. The pipe specimens were removed

from 28 underground sites having a range of soil resistivities comparable to those of the; three piling sites.

Using one of the polarization techniques applied to the individual test piles, polarization measurements were also carried out on 32 interconnected piles supporting one

of the concrete piers. The calculated average corrosion rate of the 32 piles was found

to compare favorably with that of the separate test piles in the same area.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Average penetration rate; H-piles; instantaneous corrosion rate; linear polarization;

pit depth; polarization curve.

18. AVAILABILITY STATEMENT 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

[Xl UNLIMITED. UNCL ASSIFIED 17

1 1 FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

20. SECURITY CLASS

(THIS PAGE)

22. Price

UNCLASSIFIED

30 cents

USCOMM-DC 66244.P71



NBS TECHNICAL PUBLICATIONS

PERIODICALS JOURNAL OF RESEARCH reports National

Bureau of Standards research and development in

physics, mathematics, and chemistry. Comprehensive

scientific papers give complete details of the work,

including laboratory data, experimental procedures,

and theoretical and mathematical analyses. Illustrated with photographs, drawings, and charts. Includes

listings of other NBS papers as issued.

Published in two sections, available separately:

• Physics and Chemistry

Papers of interest primarily to scientists working in these fields. This section covers a broad range of

physical and chemical research, with major emphasis on standards of physical measurement, fundamental

constants, and properties of matter. Issued six times

a year. Annual subscription: Domestic, $9.50; $2.25

additional for foreign mailing.

• Mathematical Sciences

Studies and compilations designed mainly for the mathematician and theoretical physicist. Topics in mathematical statistics, theory of experiment design,

numerical analysis, theoretical physics and chemistry, logical design and programming of computers

and computer systems. Short numerical tables. Issued

quarterly. Annual subscription: Domestic, $5.00;

$1.25 additional for foreign mailing.

TECHNICAL NEWS BULLETIN

The best single source of information concerning the Bureau's measurement, research, developmental, co- operative, and publication activities, this monthly

publication is designed for the industry-oriented

individual whose daily work involves intimate contact with science and technology

for engineers, chemists,

physicists, research managers, product-development

managers, and company executives. Includes listing of

all NBS papers as issued. Annual subscription: Domestic, $3.00; $1.00 additional for foreign mailing.

NONPERIODICALS Applied Mathematics Series. Mathematical tables, manuals, and studies. Building Science Series. Research results, test methods, and performance criteria of building materials, components, systems, and structures. Handbooks. Recommended codes of engineering

and industrial practice (including safety codes) de- veloped in cooperation with interested industries,

professional organizations, and regulatory bodies. Special Publications. Proceedings of NBS conferences, bibliographies, annual reports, wall charts,

pamphlets, etc. Monographs. Major contributions to the technical

literature on various subjects related to the Bureau's

scientific and technical activities. National Standard Reference Data Series.

NSRDS provides quantitative data on the physical

and chemical properties of materials, compiled from

the world's literature and critically evaluated. Product Standards. Provide requirements for sizes, types, quality, and methods for testing various industrial products. These standards are developed co- operatively with interested Government and industry

groups and provide the basis for common understanding of product characteristics for both buyers and

sellers. Their use is voluntary.

Technical Notes. This series consists of communications and reports (covering both other-agency and

NBS-sponsored work) of limited or transitory interest. Federal Information Processing Standards

Publications. This series is the official publication

within the Federal Government for information on

standards adopted and promulgated under the Public

Law 89—306, and Bureau of the Budget Circular A—86

entitled, Standardization of Data Elements and Codes

in Data Systems.

Consumer Information Series. Practical information, based on NBS research and experience, cover- ing areas of interest to the consumer. Easily vmderstandable language and illustrations provide useful background knowledge for shopping in today's tech- nological marketplace.

CATALOGS OF NBS PUBLICATIONS NBS Special Publication 305, Publications of

the NBS. 1966-1967. When ordering, include

Catalog No. C13.] 0:305. Price $2.00: 50 cents additional for foreign mailing.

NBS Special Publication 305, Supplement 1, Publications of the NBS, 1968-1969. When ordering, include Catalog No. C 13.10: 305/Suppl. 1. Price

$4.50; $1.25 additional for foreign mailing.

NBS Special Publication 305, Supplement 2,

Publications of the NBS, 1970. When ordering, include Catalog No. C13.10:305/Suppl. 2. Price $3.25; 85 cents additional for foreign mailing.

Bibliographic Subscription Services

The following current-awareness and literature- survey bibliographies are issued periodically by

the Bureau: Cryogenic Data Center Current

Awareness Service (weekly). Liquefied Natural

Gas (quarterly). Superconducting Devices and

Materials (quarterly), and Electromagnetic

Metrology Current Awareness Service (monthly) . Available only from NBS Boulder Laboratories. Ordering and cost information may be

obtained from the Program Information Office,

National Bureau of Standards, Boulder, Colorado 80302.

Order NBS publications (except Bibliographic Subscription Services)

from: Superintendent of Documents, Government Printing Office, Washington, D.C. 20402.
U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington. D.C. 20234

OFFICIAL BUSINESS

POSTAGE AND FEES PAID

U.S. DEPARTMENT OF COMMERCE

215

Penalty for Private Use, $300