ASTM A262-13
(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
ABSTRACT
This specification covers the standard practices for detecting susceptibility to intergranular attack in austenitic stainless steels. These practices include five intergranular corrosion tests, namely: (1) oxalic acid etch test for classification of etch structures of austenitic stainless steels; (2) ferric sulfate-sulfuric acid test, (3) nitric acid test and (4) copper-copper sulfate-sulfuric acid test for detecting susceptibility to intergranular attack in austenitic stainless steels; and (5) copper-copper sulfate-50% sulfuric acid test for detecting susceptibility to intergranular attack in molybdenum-bearing cast austenitic stainless steels. Methods for preparing the test specimens, rapid screening tests, apparatus setup and testing procedures, and calculations and report contents are described for each testing practice. The etch structure types used to classify the specimens are: step structure, dual structure, ditch structure, isolated ferrite, interdendritic ditches, end-grain pitting I, and end-grain pitting II.
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 Austenitic Stainless Steels (Sections 32 to 38, inclusive).
1.2 The oxalic acid etch test is a rapid method of identifying, by simple etching, those specimens of certain stainless steel grades that 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.” The etch test is applicable only to those grades listed in the individual hot acid tests and classifies the specimens either as “acceptable” or as “suspect.”
1.3 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 nonacceptable. Note 1—See Appendix X1 for information regarding test selection.
1.4 The values stated in SI units are to be regarded as standard. The inch-pound equivalents are in parentheses and may be approximate.
1.5 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, 11.1.9, and 35.1.)
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Designation: A262 − 13
StandardPractices for
Detecting Susceptibility to Intergranular Attack in Austenitic
1
Stainless Steels
This standard is issued under the fixed designation A262; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* based on visual examination of bend specimens and, therefore,
classifies the specimens only as acceptable or nonacceptable.
1.1 These practices cover the following five tests:
1.1.1 Practice A—Oxalic Acid Etch Test for Classification NOTE 1—See Appendix X1 for information regarding test selection.
of Etch Structures ofAustenitic Stainless Steels (Sections 3 to
1.4 The values stated in SI units are to be regarded as
7, inclusive),
standard. The inch-pound equivalents are in parentheses and
1.1.2 Practice B—Ferric Sulfate–Sulfuric Acid Test for
may be approximate.
Detecting Susceptibility to Intergranular Attack in Austenitic
1.5 This standard does not purport to address all of the
Stainless Steels (Sections 8 to 14, inclusive),
safety problems, if any, associated with its use. It is the
1.1.3 Practice C—Nitric Acid Test for Detecting Suscepti-
responsibility of the user of this standard to establish appro-
bility to Intergranular Attack in Austenitic Stainless Steels
priate safety and health practices and determine the applica-
(Sections 15 to 21, inclusive),
bility of regulatory limitations prior to use. (Specific precau-
1.1.4 Practice E—Copper–Copper Sulfate–Sulfuric Acid
tionary statements are given in 5.6, 11.1.1, 11.1.9, and 35.1.)
Test for Detecting Susceptibility to Intergranular Attack in
Austenitic Stainless Steels (Sections 22 to 31, inclusive), and
2. Referenced Documents
1.1.5 Practice F—Copper–Copper Sulfate–50% Sulfuric
2
2.1 ASTM Standards:
Acid Test for Detecting Susceptibility to Intergranular Attack
A370Test Methods and Definitions for Mechanical Testing
in Molybdenum-Bearing Austenitic Stainless Steels (Sections
of Steel Products
32 to 38, inclusive).
3
2.2 ISO Standard:
1.2 The oxalic acid etch test is a rapid method of
ISO 3651-2Determination of Resistance to Intergranular
identifying, by simple etching, those specimens of certain
Corrosion of Stainless Steels—Part 2: Ferritic,Austenitic,
stainless steel grades that are essentially free of susceptibility
and Ferritic-Austenitic (Duplex) Stainless Steels—
to intergranular attack associated with chromium carbide
Corrosion Test in Media Containing Sulfuric Acid
precipitates. These specimens will have low corrosion rates in
PRACTICE A—OXALIC ACID ETCH TEST FOR
certain corrosion tests and therefore can be eliminated
CLASSIFICATION OF ETCH STRUCTURES OF
(screened) from testing as “acceptable.” The etch test is
4
AUSTENITIC STAINLESS STEELS (1)
applicable only to those grades listed in the individual hot acid
tests and classifies the specimens either as “acceptable” or as
3. Scope
“suspect.”
3.1 The oxalic acid etch test is used for acceptance of
1.3 The ferric sulfate–sulfuric acid test, the copper–copper
material but not for rejection of material. This may be used in
sulfate–50%sulfuricacidtest,andthenitricacidtestarebased
connection with other evaluation tests to provide a rapid
on weight loss determinations and, thus, provide a quantitative
method for identifying those specimens that are certain to be
measureoftherelativeperformanceofspecimensevaluated.In
freeofsusceptibilitytorapidintergranularattackintheseother
contrast, the copper–copper sulfate–16% sulfuric acid test is
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
1
These practices are under the jurisdiction of ASTM Committee A01 on Steel, Standards volume information, refer to the standard’s Document Summary page on
StainlessSteelandRelatedAlloysandarethedirectresponsibilityofSubcommittee the ASTM website.
3
A01.14 on Methods of Corrosion Testing. Available from International Organization for Standardization (ISO), 1 rue de
Current edition approved May 1, 2013. Published June 2013. Originally Varembé, Case postale 56, CH-1211, Geneva 20, Switzerland, http://www.iso.ch.
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approved in 1943. Last previous edition approved in 2010 as A262–10. DOI: The boldface numbers in parentheses refer to a list of references at the end of
10.1520/A0262-13. this standard.
*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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This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: A262 − 10 A262 − 13
Standard Practices for
Detecting Susceptibility to Intergranular Attack in Austenitic
1
Stainless Steels
This standard is issued under the fixed designation A262; 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 (´) 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*
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 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.
1.2 The oxalic acid etch test is a rapid method of identifying, by simple etching, those specimens of certain stainless steel grades
that 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.”
The etch test is applicable only to those grades listed in the individual hot acid tests and classifies the specimens either as
“acceptable” or as “suspect.”
1.3 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 nonacceptable.
NOTE 1—See Appendix X1 for information regarding test selection.
1.5 In most cases either the 15-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
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.
Current edition approved April 1, 2010May 1, 2013. Published April 2010June 2013. Originally approved in 1943. Last previous edition approved in 20082010 as
A262 – 02a (2008).A262 – 10. DOI: 10.1520/A0262-10.10.1520/A0262-13.
*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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A262 − 13
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 that might be subject to e
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