ASTM A262-02ae2
(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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e2
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
e NOTE—Table 1 was editorially corrected in August 2004.
2
e NOTE—Section 30.1.5.1 was editorially corrected in January 2005.
1. Scope* 1.3 The oxalic acid etch test is a rapid method of identify-
ing, by simple etching, those specimens of certain stainless
1.1 These practices cover the following five tests:
steel grades that are essentially free of susceptibility to
1.1.1 Practice A—Oxalic Acid Etch Test for Classification
intergranular attack associated with chromium carbide precipi-
of Etch Structures of Austenitic Stainless Steels (Sections 3 to
tates. These specimens will have low corrosion rates in certain
7, inclusive),
corrosion tests and therefore can be eliminated (screened) from
1.1.2 Practice B—Ferric Sulfate–Sulfuric Acid Test for
testing as “acceptable.”
Detecting Susceptibility to Intergranular Attack in Austenitic
1.4 The ferric sulfate–sulfuric acid test, the copper–copper
Stainless Steels (Sections 8 to 14, inclusive),
sulfate–50 %sulfuricacidtest,andthenitricacidtestarebased
1.1.3 Practice C—Nitric Acid Test for Detecting Suscepti-
on weight loss determinations and, thus, provide a quantitative
bility to Intergranular Attack in Austenitic Stainless Steels
measureoftherelativeperformanceofspecimensevaluated.In
(Sections 15 to 21, inclusive),
contrast, the copper–copper sulfate–16 % sulfuric acid test is
1.1.4 Practice E—Copper–Copper Sulfate–Sulfuric Acid
based on visual examination of bend specimens and, therefore,
Test for Detecting Susceptibility to Intergranular Attack in
classifies the specimens only as acceptable or nonacceptable.
Austenitic Stainless Steels (Sections 22 to 31, inclusive), and
1.5 In most cases either the 24-h copper–copper sul-
1.1.5 Practice F—Copper–Copper Sulfate–50 % Sulfuric
fate–16 % sulfuric acid test or the 120-h ferric sulfate–sulfuric
Acid Test for Detecting Susceptibility to Intergranular Attack
acid test, combined with the oxalic acid etch test, will provide
in Molybdenum-Bearing CastAustenitic Stainless Steels (Sec-
the required information in the shortest time. All stainless
tions 32 to 38, inclusive).
grades listed in the accompanying table may be evaluated in
1.2 The following factors govern the application of these
these combinations of screening and corrosion tests, except
practices:
those specimens of molybdenum-bearing grades (for example
1.2.1 Susceptibility to intergranular attack associated with
316, 316L, 317, and 317L), which represent steel intended for
theprecipitationofchromiumcarbidesisreadilydetectedinall
use in nitric acid environments.
six tests.
1.6 The 240-h nitric acid test must be applied to stabilized
1.2.2 Sigma phase in wrought chromium-nickel-
and molybdenum-bearing grades intended for service in nitric
molybdenum steels, which may or may not be visible in the
acidandtoallstainlesssteelgradesthatmightbesubjecttoend
microstructure, can result in high corrosion rates only in nitric
grain corrosion in nitric acid service.
acid.
1.7 Only those stainless steel grades are listed in Table 1 for
1.2.3 Sigma phase in titanium or columbium stabilized
whichdataontheapplicationoftheoxalicacidetchtestandon
alloys and cast molybdenum-bearing stainless alloys, which
their performance in various quantitative evaluation tests are
may or may not be visible in the microstructure, can result in
available.
high corrosion rates in both the nitric acid and ferric sulfate-
1.8 Extensive test results on various types of stainless steels
–sulfuric acid solutions.
2
evaluated by these practices have been published in Ref (1).
1
These practices are under the jurisdiction of ASTM Committee A01 on Steel,
Stainless Steel and RelatedAlloys 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 boldface numbers in parentheses refer to the list of references found at the
approved in 1943. Last previous edition approved in 2002 as A 262 – 02. end of these practices.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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