ASTM A262-15(2021)

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.
SIGNIFICANCE AND USE
6.1 Use of the etch test allows rapid acceptance of specific lots of material without the need to perform time-consuming and costly hot acid immersion tests on those lots.
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 4 to 13, inclusive),  
1.1.2 Practice B—Ferric Sulfate-Sulfuric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (Sections 14 to 25, inclusive),  
1.1.3 Practice C—Nitric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (Sections 26 to 36, inclusive),  
1.1.4 Practice E—Copper–Copper Sulfate–Sulfuric Acid Test for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (Sections 37 to 46, 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 47 to 58, 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.  
1.4 The presence or absence of intergranular attack in these tests is not necessarily a measure of the performance of the material in other corrosive environments. These tests do not provide a basis for predicting resistance to forms of corrosion other than intergranular, such as general corrosion, pitting, or stress-corrosion cracking.
Note 1: See Appendix X1 for information regarding test selection.  
1.5 The values stated in SI units are to be regarded as standard. The inch-pound equivalents are in parentheses and may be approximate.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitatio...

General Information

• Status: Published
• Publication Date: 31-Aug-2021
• ICS: 77.140.20 - Stainless steels
• Technical Committee: A01 - Steel, Stainless Steel and Related Alloys
• Drafting Committee: A01.14 - Methods of Corrosion Testing

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: A262 − 15 (Reapproved 2021)
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.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:
1.4 The presence or absence of intergranular attack in these
1.1.1 Practice A—Oxalic Acid Etch Test for Classification
of Etch Structures ofAustenitic Stainless Steels (Sections 4 to tests is not necessarily a measure of the performance of the
material in other corrosive environments. These tests do not
13, inclusive),
provide a basis for predicting resistance to forms of corrosion
1.1.2 Practice B—Ferric Sulfate-Sulfuric Acid Test for De-
other than intergranular, such as general corrosion, pitting, or
tecting Susceptibility to Intergranular Attack in Austenitic
Stainless Steels (Sections 14 to 25, inclusive), stress-corrosion cracking.
1.1.3 Practice C—Nitric Acid Test for Detecting Suscepti-
NOTE 1—See Appendix X1 for information regarding test selection.
bility to Intergranular Attack in Austenitic Stainless Steels
1.5 The values stated in SI units are to be regarded as
(Sections 26 to 36, inclusive),
standard. The inch-pound equivalents are in parentheses and
1.1.4 Practice E—Copper–Copper Sulfate–Sulfuric Acid
may be approximate.
Test for Detecting Susceptibility to Intergranular Attack in
1.6 This standard does not purport to address all of the
Austenitic Stainless Steels (Sections 37 to 46, inclusive), and
safety concerns, if any, associated with its use. It is the
1.1.5 Practice F—Copper–Copper Sulfate–50% Sulfuric
responsibility of the user of this standard to establish appro-
Acid Test for Detecting Susceptibility to Intergranular Attack
priate safety, health, and environmental practices and deter-
in Molybdenum-Bearing Austenitic Stainless Steels (Sections
mine the applicability of regulatory limitations prior to use.
47 to 58, inclusive).
Some specific hazards statements are given in 10.1, 20.1.1,
1.2 The Oxalic Acid Etch Test is a rapid method of
20.1.9, 31.3, 34.4, 53.1.1, and 53.1.10.
identifying, by simple etching, those specimens of certain
1.7 This international standard was developed in accor-
stainless steel grades that are essentially free of susceptibility
dance with internationally recognized principles on standard-
to intergranular attack associated with chromium carbide
ization established in the Decision on Principles for the
precipitates. These specimens will have low corrosion rates in
Development of International Standards, Guides and Recom-
certain corrosion tests and therefore can be eliminated
mendations issued by the World Trade Organization Technical
(screened) from testing as “acceptable.” The etch test is
Barriers to Trade (TBT) Committee.
applicable only to those grades listed in the individual hot acid
tests and classifies the specimens either as “acceptable” or as
2. Referenced Documents
“suspect.”
2
2.1 ASTM Standards:
1.3 The ferric sulfate-sulfuric acid test, the copper–copper
A370Test Methods and Definitions for Mechanical Testing
sulfate–50%sulfuricacidtest,andthenitricacidtestarebased
of Steel Products
on weight loss determinations and, thus, provide a quantitative
A380/A380MPractice for Cleaning, Descaling, and Passi-
measureoftherelativeperformanceofspecimensevaluated.In
vation of Stainless Steel Parts, Equipment, and Systems
contrast, the copper–copper sulfate–16% sulfuric acid test is
D1193Specification for Reagent Water
E3Guide for Preparation of Metallographic Specimens
1
These practices are under the jurisdiction of ASTM Committee A01 on Steel,
StainlessSteelandRelatedAlloysandarethedirectresponsibilityofSubcommittee
2
A01.14 on Methods of Corrosion Testing. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Sept. 1, 2021. Published September 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1943. Last previous edition approved in 2015 as A262–15. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/A0262-15R21. the ASTM website.
*A Summary of Changes
...