ASTM A262-02a(2008)

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 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 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.”  
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 nonacceptable.
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.  
1.6 The 240...

General Information

• Status: Historical
• Publication Date: 29-Feb-2008
• ICS: 77.140.20 - Stainless steels
• Technical Committee: A01 - Steel, Stainless Steel and Related Alloys
• Drafting Committee: A01.14 - Methods of Corrosion Testing

Relations

• Replaces: ASTM A262-02ae3 - Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
• Effective Date: 01-Mar-2008
• Replaced By: ASTM A262-10 - Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
• Effective Date: 01-Apr-2010
• Referred By: ASTM G28-22 - Standard Test Methods for Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys
• Effective Date: 01-Mar-2008
• Referred By: ASTM F593-22 - Standard Specification for Stainless Steel Bolts, Hex Cap Screws, and Studs
• Effective Date: 01-Mar-2008
• Referred By: ASTM F621-12(2021)e1 - Standard Specification for Stainless Steel Forgings for Surgical Implants
• Effective Date: 01-Mar-2008
• Referred By: ASTM G48-11(2020)e1 - Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution
• Effective Date: 01-Mar-2008
• Referred By: ASTM G108-23 - Standard Test Methods for Electrochemical Reactivation (EPR) for Detecting Sensitization of AISI Type 304 and 304L Stainless Steels
• Effective Date: 01-Mar-2008
• Referred By: ASTM F837-20 - Standard Specification for Stainless Steel Socket Head Cap Screws
• Effective Date: 01-Mar-2008
• Referred By: ASTM A632-19 - Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing (Small-Diameter) for General Service
• Effective Date: 01-Mar-2008
• Referred By: ASTM A688/A688M-18(2022) - Standard Specification for Seamless and Welded Austenitic Stainless Steel Feedwater Heater Tubes
• Effective Date: 01-Mar-2008
• Referred By: ASTM B474/B474M-19 - Standard Specification for Electric Fusion Welded Nickel and Nickel Alloy Pipe
• Effective Date: 01-Mar-2008
• Referred By: ASTM B906-22 - Standard Specification for General Requirements for Flat-Rolled Nickel and Nickel Alloys Plate, Sheet, and Strip
• Effective Date: 01-Mar-2008
• Referred By: ASTM A409/A409M-19 - Standard Specification for Welded Large Diameter Austenitic Steel Pipe for Corrosive or High-Temperature Service
• Effective Date: 01-Mar-2008
• Referred By: ASTM A960/A960M-23 - Standard Specification for Common Requirements for Wrought Steel Piping Fittings
• Effective Date: 01-Mar-2008
• Referred By: ASTM A182/A182M-23 - Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service
• Effective Date: 01-Mar-2008

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation: A262 – 02a (Reapproved 2008)
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 intergranular attack associated with chromium carbide precipi-
tates. These specimens will have low corrosion rates in certain
1.1 These practices cover the following five tests:
corrosion tests and therefore can be eliminated (screened) from
1.1.1 Practice A—Oxalic Acid Etch Test for Classification
testing as “acceptable.”
of Etch Structures of Austenitic Stainless Steels (Sections 3 to
1.4 The ferric sulfate–sulfuric acid test, the copper–copper
7, inclusive),
sulfate–50 %sulfuricacidtest,andthenitricacidtestarebased
1.1.2 Practice B—Ferric Sulfate–Sulfuric Acid Test for
on weight loss determinations and, thus, provide a quantitative
Detecting Susceptibility to Intergranular Attack in Austenitic
measureoftherelativeperformanceofspecimensevaluated.In
Stainless Steels (Sections 8 to 14, inclusive),
contrast, the copper–copper sulfate–16 % sulfuric acid test is
1.1.3 Practice C—Nitric Acid Test for Detecting Suscepti-
based on visual examination of bend specimens and, therefore,
bility to Intergranular Attack in Austenitic Stainless Steels
classifies the specimens only as acceptable or nonacceptable.
(Sections 15 to 21, inclusive),
1.5 In most cases either the 15-h copper–copper sul-
1.1.4 Practice E—Copper–Copper Sulfate–Sulfuric Acid
fate–16 % sulfuric acid test or the 120-h ferric sulfate–sulfuric
Test for Detecting Susceptibility to Intergranular Attack in
acid test, combined with the oxalic acid etch test, will provide
Austenitic Stainless Steels (Sections 22 to 31, inclusive), and
the required information in the shortest time. All stainless
1.1.5 Practice F—Copper–Copper Sulfate–50 % Sulfuric
grades listed in the accompanying table may be evaluated in
Acid Test for Detecting Susceptibility to Intergranular Attack
these combinations of screening and corrosion tests, except
in Molybdenum-Bearing CastAustenitic Stainless Steels (Sec-
those specimens of molybdenum-bearing grades (for example
tions 32 to 38, inclusive).
316, 316L, 317, and 317L), which represent steel intended for
1.2 The following factors govern the application of these
use in nitric acid environments.
practices:
1.6 The 240-h nitric acid test must be applied to stabilized
1.2.1 Susceptibility to intergranular attack associated with
and molybdenum-bearing grades intended for service in nitric
theprecipitationofchromiumcarbidesisreadilydetectedinall
acidandtoallstainlesssteelgradesthatmightbesubjecttoend
six tests.
grain corrosion in nitric acid service.
1.2.2 Sigma phase in wrought chromium-nickel-
1.7 Only those stainless steel grades are listed inTable 1 for
molybdenum steels, which may or may not be visible in the
whichdataontheapplicationoftheoxalicacidetchtestandon
microstructure, can result in high corrosion rates only in nitric
their performance in various quantitative evaluation tests are
acid.
available.
1.2.3 Sigma phase in titanium or columbium stabilized
1.8 Extensive test results on various types of stainless steels
alloys and cast molybdenum-bearing stainless alloys, which
2
evaluated by these practices have been published in Ref (1).
may or may not be visible in the microstructure, can result in
1.9 The values stated in SI units are to be regarded as
high corrosion rates in both the nitric acid and ferric sulfate-
standard. The inch-pound equivalents are in parentheses and
–sulfuric acid solutions.
may be approximate.
1.3 The oxalic acid etch test is a rapid method of identify-
1.10 This standard does not purport to address all of the
ing, by simple etching, those specimens of certain stainless
safety problems, if any, associated with its use. It is the
steel grades that are essentially free of susceptibility to
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. (Specific precau-
1
These practices are under the jurisdiction of ASTM Committee A01 on Steel,
tionary statements are given in 5.6, 11.1.1, 11.1.9, and 35.1.)
Stainless Steel and RelatedAlloys and are the direct responsibility of Subcommittee
A01.14 on Methods of Corrosion Testing.
Current edition approved March 1, 2008. Published March 2008. Originally
´3 2
approved in 1943. Last previous edition approv
...

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.
An American National Standard Designation: A 262 – 02a (Reapproved 2008)
Designation:A 262–02
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
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–SulfuricAcid Test for Detecting Susceptibility to IntergranularAttack inAustenitic 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–SulfuricAcid Test for Detecting Susceptibility to IntergranularAttack inAustenitic
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 Sigmaphaseinwroughtchromium-nickel-molybdenumsteels,whichmayormaynotbevisibleinthemicrostructure,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 Theoxalicacidetchtestisarapidmethodofidentifying,bysimpleetching,thosespecimensofcertainstainlesssteelgrades
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.”
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 nonacceptable.
1.5 In most cases either the 24-h15-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 that 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.
2
1.8 Extensive test results on various types of stainless steels evaluated by these practices have been published in Ref (1).
1
These practices are under the jurisdiction ofASTM CommitteeA01 on Steel, Stainless Steel and RelatedAlloys and are the direct responsibility of SubcommitteeA01.14
on Methods of Corrosion Testing.
Current edition approved June 10, 2002. Published August 2002. Originally published as A262–43T. Last previous edition A262–01.
e3
Current edition approved March 1, 2008. Published March 2008. Originally approved in 1943. Last previous edition approved in 2002 as A 262 – 02a .
2
The boldface numbers i
...