ASTM A262-02a
(Practice)Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
SCOPE
1.1 These practices cover the following five tests:
1.1.1 Practice A— Oxalic Acid Etch Test for Classification of Etch Structures of Austenitic Stainless Steels (Sections 3 to 7, inclusive),
1.1.2 Practice B—Ferric Sulfate-Sulfuric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (Sections 8 to 14, inclusive),
1.1.3 Practice C—Nitric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (Sections 15 to 21, inclusive),
1.1.4 Practice E—Copper-Copper Sulfate-Sulfuric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (Sections 22 to 31, inclusive), and
1.1.5 Practice F—Copper-Copper Sulfate-50% Sulfuric Acid Test for Detecting Susceptibility to Intergranular Attack in Molybdenum-Bearing Cast Austenitic Stainless Steels (Sections 32 to 38, inclusive).
1.2 The following factors govern the application of these practices:
1.2.1 Susceptibility to intergranular attack associated with the precipitation of chromium carbides is readily detected in all six tests.
1.2.2 Sigma phase in wrought chromium-nickel-molybdenum steels, which may or may not be visible in the microstructure, can result in high corrosion rates only in nitric acid.
1.2.3 Sigma phase in titanium or columbium stabilized alloys and cast molybdenum bearing stainless alloys, which may or may not be visible in the microstructure, can result in high corrosion rates in both the nitric acid and ferric sulfate-sulfuric acid solutions.
1.3 The oxalic acid etch test is a rapid method of identifying, by simple etching, those specimens of certain stainless steel grades which are essentially free of susceptibility to intergranular attack associated with chromium carbide precipitates. These specimens will have low corrosion rates in certain corrosion tests and therefore can be eliminated (screened) from testing as "acceptable."
1.4 The ferric sulfate-sulfuric acid test, the copper-copper sulfate-50% sulfuric acid test, and the nitric acid test are based on weight loss determinations and, thus, provide a quantitative measure of the relative performance of specimens evaluated. In contrast, the copper-copper sulfate-16% sulfuric acid test is based on visual examination of bend specimens and, therefore, classifies the specimens only as acceptable or non-acceptable.
1.5 In most cases either the 24-h copper-copper sulfate-16% sulfuric acid test or the 120-h ferric sulfate-sulfuric acid test, combined with the oxalic acid etch test, will provide the required information in the shortest time. All stainless grades listed in the accompanying table may be evaluated in these combinations of screening and corrosion tests, except those specimens of molybdenum-bearing grades (for example 316, 316L, 317, and 317L), which represent steel intended for use in nitric acid environments.
1.6 The 240-h nitric acid test must be applied to stabilized and molybdenum-bearing grades intended for service in nitric acid and to all stainless steel grades which might be subject to end grain corrosion in nitric acid service.
1.7 Only those stainless steel grades are listed in Table 1 for which data on the application of the oxalic acid etch test and on their performance in various quantitative evaluation tests are available.
1.8 Extensive test results on various types of stainless steels evaluated by these practices have been published in Ref (1).
1.9 The values stated in SI units are to be regarded as standard. The inch-pound equivalents are in parentheses and may be approximate.
1.10 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (Specific precautionary statements are given in 5.6, 11.1.1, ...
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Designation: A 262 – 02a
Standard Practices for
Detecting Susceptibility to Intergranular Attack in Austenitic
1
Stainless Steels
This standard is issued under the fixed designation A 262; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope* tates. These specimens will have low corrosion rates in certain
corrosion tests and therefore can be eliminated (screened) from
1.1 These practices cover the following five tests:
testing as “acceptable.”
1.1.1 Practice A—Oxalic Acid Etch Test for Classification
1.4 The ferric sulfate–sulfuric acid test, the copper–copper
of Etch Structures of Austenitic Stainless Steels (Sections 3 to
sulfate–50 % sulfuric acid test, and the nitric acid test are based
7, inclusive),
on weight loss determinations and, thus, provide a quantitative
1.1.2 Practice B—Ferric Sulfate–Sulfuric Acid Test for
measure of the relative performance of specimens evaluated. In
Detecting Susceptibility to Intergranular Attack in Austenitic
contrast, the copper–copper sulfate–16 % sulfuric acid test is
Stainless Steels (Sections 8 to 14, inclusive),
based on visual examination of bend specimens and, therefore,
1.1.3 Practice C—Nitric Acid Test for Detecting Suscepti-
classifies the specimens only as acceptable or nonacceptable.
bility to Intergranular Attack in Austenitic Stainless Steels
1.5 In most cases either the 24-h copper–copper sul-
(Sections 15 to 21, inclusive),
fate–16 % sulfuric acid test or the 120-h ferric sulfate–sulfuric
1.1.4 Practice E—Copper–Copper Sulfate–Sulfuric Acid
acid test, combined with the oxalic acid etch test, will provide
Test for Detecting Susceptibility to Intergranular Attack in
the required information in the shortest time. All stainless
Austenitic Stainless Steels (Sections 22 to 31, inclusive), and
grades listed in the accompanying table may be evaluated in
1.1.5 Practice F—Copper–Copper Sulfate–50 % Sulfuric
these combinations of screening and corrosion tests, except
Acid Test for Detecting Susceptibility to Intergranular Attack
those specimens of molybdenum-bearing grades (for example
in Molybdenum-Bearing Cast Austenitic Stainless Steels (Sec-
316, 316L, 317, and 317L), which represent steel intended for
tions 32 to 38, inclusive).
use in nitric acid environments.
1.2 The following factors govern the application of these
1.6 The 240-h nitric acid test must be applied to stabilized
practices:
and molybdenum-bearing grades intended for service in nitric
1.2.1 Susceptibility to intergranular attack associated with
acid and to all stainless steel grades that might be subject to end
the precipitation of chromium carbides is readily detected in all
grain corrosion in nitric acid service.
six tests.
1.7 Only those stainless steel grades are listed in Table 1 for
1.2.2 Sigma phase in wrought chromium-nickel-
which data on the application of the oxalic acid etch test and on
molybdenum steels, which may or may not be visible in the
their performance in various quantitative evaluation tests are
microstructure, can result in high corrosion rates only in nitric
available.
acid.
1.8 Extensive test results on various types of stainless steels
1.2.3 Sigma phase in titanium or columbium stabilized
2
evaluated by these practices have been published in Ref (1).
alloys and cast molybdenum-bearing stainless alloys, which
1.9 The values stated in SI units are to be regarded as
may or may not be visible in the microstructure, can result in
standard. The inch-pound equivalents are in parentheses and
high corrosion rates in both the nitric acid and ferric sulfate-
may be approximate.
–sulfuric acid solutions.
1.10 This standard does not purport to address all of the
1.3 The oxalic acid etch test is a rapid method of identify-
safety problems, if any, associated with its use. It is the
ing, by simple etching, those specimens of certain stainless
responsibility of the user of this standard to establish appro-
steel grades that are essentially free of susceptibility to
priate safety and health practices and determine the applica-
intergranular attack associated with chromium carbide precipi-
bility of regulatory limitations prior to use. (Specific precau-
tionary statements are given in 5.6, 11.1.1, 11.1.9, and 35.1.)
1
These practices are under the jurisdiction of ASTM Committee A01 on Steel,
Stainless Steel and Related Alloys and are the direct responsibility of Subcommittee
A01.14 on Methods of Corrosion Testing.
2
Current edition approved Nov. 10, 2002. Published December 2002. Originally The bold
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