TECHNICAL INFORMATION ON BUILDING MATERIALS

FOR USE IN THE DESIGN OF LOW-COST HOUSING TIBM - 50

* * * >)( * t|c * *

THE NATIONAL BUREAU OF STANDARDS

UNITED STATES DEPARTMENT OF COMMERCE

WASHINGTON, D. C.

July 15, 19^7

CORROSION OF NONFERROUS METALS UNDERGROUND

The corrosion of ferrous metals underground is discussed in

TIBM-29, "Corrosion of Ferrous Metals Underground. " ^ It describes

the investigation of such corrosion by the National Bureau of

Standards and is a digest of Research Paper RPSS3* "Soil-Corrosion

Studies, 193 U. Rates of Loss of Weight and Pitting of Ferrous

Specimens," by Kirk H. Logan. ^ When the work was started in 1922

most of the metals studied were ferrous. As the study progressed,

it was found that in certain soils the corrosion of iron and steel

was very severe. This suggested the desirability of investigating

the durability in these soils of other metals frequently used underground, such as copper and lead alloys, like brass, or metallic

coatings for iron and steel, such as lead and zinc. Through the

cooperation of manufacturers, representative pipe or sheet materials

were obtained, and these were buried in various soils, usually at

times when the ferrous metals under test were being removed. A

Bureau report, Research Paner RP9H5 , "Soil-Corrosion Studies, 193^-*

Rates of Loss of Weight and Penetration of NonFerrous Materials,"

by Kirk H. Logan, ^ showing the behavior of several nonferrous

materials in various soils after two to ten years exposure, has

recently been prepared and the findings of this report are the

basis of this TIBM.

^May be obtained, free of charge, from the Division of Codes

and Specifications, National Bureau of Standards, Washington, D. C.

pMay be obtained from Superintendent of Documents, Washington,

D. C. (Price 5 cents)

^May be obtained from Superintendent of Documents, Washington.

D. C. (Price 10 cents)

1
The important characteristics of soil corrosion and the features

differentiating soil corrosion from atmospheric or submerged water

corrosion are given in TIBM-29 , previously referred to. Soil

charac terti stic s, such as texture, drainage, salts present, composition of soil atmosphere, acid or alkaline character of soil water,

water-holding power, and other factors peculiar to the soil environment, determine the nature and extent of corrosion of ferrous

metals. 1 This has been found to be equally true for the corrosion

of nonferrous metals. The Bureau investigations have also reached

the point where it is possible in certain cases to examine an un- known soil in the laboratory for some of these characteristics and

thus predetermine its corrosiveness toward nonferrous metals, as has been done for the ferrous metals.

All conclusions about the corrosion of nonferrous metals in

soil are, at this time, somewhat tentative because; first, not

enough samples have been investigated in all soils and because,

second, the corrosion period in many cases is too short. With due

allowance made for these restrictions, the following conclusions

have been expressed on nonferrous metal corrosion in soils:

1. No one metal or alloy has been found superior to all others

for all soil conditions, but for each condition some suitable metal

is available.

2. With but few exceptions the rates of loss of weight and of

penetration by pitting are less for the nonferrous specimens than

for ferrous specimens in the same soil environment.

3* Lead in some soils pits badly, as a result of causes not

fully known at this time. The presence of chlorides, bicarbonates,

and particularly sulphates in soils favors the formation of films

or deposits on the lead which tend to retard its corrosion. In

such soils the corrosion rate generally decreases with time, but

in other soils, such as marshes, the corrosion rate remains practically constant. Lead-coated steel pipes corrode much faster after

penetration of the lead than uncoated steel pipes. (See TIBM-17,

"Corrosion of Metals Used in House Construction; Atmospheric

Corrosion of Galvanized ferrous Sheet Metals,"^ for an explanation

of this behavior).

The Bureau report, (RP9U 5 ) before mentioned, on the corrosion

of nonferrous metals, contains a table giving numerical data on properties mentioned for several soils that were investigated.

2

May be obtained, free of charge, from the Division of Codes

and Specifications, National Bureau of Standards, Washington, D. C.
4. Copoer and high-copper brasses corrode slowly in most of the

soils studied. The corrosion of these metals is more uniform than that

of ferrous metals in similar soils, and there is less change in the

rates of corrosion than for those of ferrous metals. The soils most

destructive to couper or brass are those containing sulphides.

5. The brasses of lower Conner content show a distinct tendency

to "dezincify" i.e., a selective dissolving away of zinc. This is

shown particularly in Table 2, page 5* ‘Because such corrosion results

in porosity and marked reduction in strength, it is to be considered

very detrimental for many uses of the pipe ('or fittings) such, for

instance, as conveying water under, high pressure.

6. Comparison of pitting rates', of galvanized as against nongal vani zed steel, Table 1, page 4 , shows that, in four out of the

five soils tabulated, pitting was much less for galvanized steel.

From these conclusions it will be noted that the commonly used

aoaferrous metals generally corrode differently in the same soil.

This is in decided contrast to ferrous metals, all of which corrode

similarly in a given soil (See TIBM-29),

Table 1 gives details of the ten-year test, Table 2 of the twoyear test, and Table 3 contains a brief description of the metals

included in the tests.

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TABLE 3

DESCRIPTION OE METALS

Metals' Shown in Table 1

Metal Eorm Dimensions Composition

Lead Cast

Inches

6 x 2 x 0.25

Percent

99.9 Fb, .07 Cu, .005 Ag

Copper Shee t 6 x 2 x .05 99* Cu

Brass Sheet 6 x 2 x .05 70 Cu, 30 Zn

Steel Sheet 6x2 Cooper bearing steel,

G-alvani zed Sheet 6 x 12

apurox. 0.2 Cu

Coating of 1.62 oz. zinc

Steel per sq. ft. of sheet.

Lead Coated Pipe 1 1/2 x 6

Base metal: C .07, Mn .37

P .097, S .067, Si .01,

Cu .003

Pb coating between .001"

Steel v and .002" thick

Metals Shown in Table 2

Metal Eorm Dimensions Composition

Deoxi di zed

Copper

Pipe

Inches

1.7 diam. , . l44

wall, 13 long

Pe rcent

99.94 Cu, .013 P

Red Brass Pipe 1.7 diam., .143

wall, 13 long

35.13 Cu, 14.8 Zn, 0.01 Ee

Brass Pipe 1.7 diam., . 1U 5

wall, 13 long

66,5 Cu, 33.06 Zn, 0.42 Fb

0.02 Ee

Admiralty

Metal

Pipe 1.7 diam., .143

wall, 12 long

71.28 Cu, 27.39 Zn, 1.3 Sn

0.01 Pb, 0.02 5b

Muntz

Metal

Pipe 1. 7 diam. , 0.03

wall, 12 long

60.06 Cu, 39.58 Zn, 0.36 F

trace 5b

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