ASTM A262-10

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 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-h ni...

General Information

• Status: Historical
• Publication Date: 31-Mar-2010
• 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 A262-02a(2008) - Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
• Effective Date: 01-Apr-2010
• Replaced By: ASTM A262-13 - Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
• Effective Date: 01-May-2013
• Referred By: ASTM B853-16(2021)e1 - Standard Specification for Powder Metallurgy (PM) Boron Stainless Steel Structural Components
• Effective Date: 01-Apr-2010
• Referred By: ASTM A743/A743M-21 - Standard Specification for Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application
• Effective Date: 01-Apr-2010
• Referred By: ASTM F1314-18 - Standard Specification for Wrought Nitrogen Strengthened 22 Chromium–13 Nickel–5 Manganese–2.5 Molybdenum Stainless Steel Alloy Bar and Wire for Surgical Implants (UNS S20910)
• Effective Date: 01-Apr-2010
• Referred By: ASTM B464/B464M-15(2020) - Standard Specification for Welded UNS N08020 Alloy Pipe
• Effective Date: 01-Apr-2010
• Referred By: ASTM A815/A815M-23 - Standard Specification for Wrought Ferritic, Ferritic/Austenitic, and Martensitic Stainless Steel Piping Fittings
• Effective Date: 01-Apr-2010
• Referred By: ASTM F138-19 - Standard Specification for Wrought 18Chromium-14Nickel-2.5Molybdenum Stainless Steel Bar and Wire for Surgical Implants (UNS S31673)
• Effective Date: 01-Apr-2010
• Referred By: ASTM F3160-21 - Standard Guide for Metallurgical Characterization of Absorbable Metallic Materials for Medical Implants
• Effective Date: 01-Apr-2010
• Referred By: ASTM F593-22 - Standard Specification for Stainless Steel Bolts, Hex Cap Screws, and Studs
• Effective Date: 01-Apr-2010
• Referred By: ASTM A479/A479M-23a - Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels
• Effective Date: 01-Apr-2010
• Referred By: ASTM F2181-20 - Standard Specification for Wrought Seamless Stainless Steel Tubing for Surgical Implants
• Effective Date: 01-Apr-2010
• 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-Apr-2010
• Referred By: ASTM F3226/F3226M-19 - Standard Specification for Metallic Press-Connect Fittings for Piping and Tubing Systems
• Effective Date: 01-Apr-2010
• Referred By: ASTM A688/A688M-18(2022) - Standard Specification for Seamless and Welded Austenitic Stainless Steel Feedwater Heater Tubes
• Effective Date: 01-Apr-2010

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 − 10
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 Department of Defense.
1. Scope* stainless steel grades that are essentially free of susceptibility
to intergranular attack associated with chromium carbide
1.1 These practices cover the following five tests:
precipitates. These specimens will have low corrosion rates in
1.1.1 Practice A—Oxalic Acid Etch Test for Classification
certain corrosion tests and therefore can be eliminated
of Etch Structures ofAustenitic Stainless Steels (Sections 3 to
(screened) from testing as “acceptable.”
7, inclusive),
1.1.2 Practice B—Ferric Sulfate–Sulfuric Acid Test for 1.4 The ferric sulfate–sulfuric acid test, the copper–copper
Detecting Susceptibility to Intergranular Attack in Austenitic sulfate–50%sulfuricacidtest,andthenitricacidtestarebased
Stainless Steels (Sections 8 to 14, inclusive), on weight loss determinations and, thus, provide a quantitative
1.1.3 Practice C—Nitric Acid Test for Detecting Suscepti- measureoftherelativeperformanceofspecimensevaluated.In
bility to Intergranular Attack in Austenitic Stainless Steels contrast, the copper–copper sulfate–16% sulfuric acid test is
(Sections 15 to 21, inclusive), based on visual examination of bend specimens and, therefore,
1.1.4 Practice E—Copper–Copper Sulfate–Sulfuric Acid classifies the specimens only as acceptable or nonacceptable.
Test for Detecting Susceptibility to Intergranular Attack in
1.5 In most cases either the 15-h copper–copper sul-
Austenitic Stainless Steels (Sections 22 to 31, inclusive), and
fate–16% sulfuric acid test or the 120-h ferric sulfate–sulfuric
1.1.5 Practice F—Copper–Copper Sulfate–50% Sulfuric
acid test, combined with the oxalic acid etch test, will provide
Acid Test for Detecting Susceptibility to Intergranular Attack
the required information in the shortest time. All stainless
in Molybdenum-Bearing Austenitic Stainless Steels (Sections
grades listed in the accompanying table may be evaluated in
32 to 38, inclusive).
these combinations of screening and corrosion tests, except
1.2 The following factors govern the application of these those specimens of molybdenum-bearing grades (for example
practices: 316, 316L, 317, and 317L), which represent steel intended for
1.2.1 Susceptibility to intergranular attack associated with use in nitric acid environments.
theprecipitationofchromiumcarbidesisreadilydetectedinall
1.6 The 240-h nitric acid test must be applied to stabilized
six tests.
and molybdenum-bearing grades intended for service in nitric
1.2.2 Sigma phase in wrought chromium-nickel-
acidandtoallstainlesssteelgradesthatmightbesubjecttoend
molybdenum steels, which may or may not be visible in the
grain corrosion in nitric acid service.
microstructure, can result in high corrosion rates only in nitric
1.7 OnlythosestainlesssteelgradesarelistedinTable1for
acid.
whichdataontheapplicationoftheoxalicacidetchtestandon
1.2.3 Sigma phase in titanium or columbium stabilized
their performance in various quantitative evaluation tests are
alloys and cast molybdenum-bearing stainless alloys, which
available.
may or may not be visible in the microstructure, can result in
high corrosion rates in both the nitric acid and ferric sulfate-
1.8 Extensive test results on various types of stainless steels
2
sulfuric acid solutions. evaluated by these practices have been published in Ref (1).
1.3 The oxalic acid etch test is a rapid method of
1.9 The values stated in SI units are to be regarded as
identifying, by simple etching, those specimens of certain standard. The inch-pound equivalents are in parentheses and
may be approximate.
1.10 This standard does not purport to address all of the
1
These practices are under the jurisdiction of ASTM Committee A01 on Steel,
safety problems, if any, associated with its use. It is the
StainlessSteelandRelatedAlloysandarethedirectresponsibilityofSubcommittee
A01.14 on Methods of Corrosion Testing.
Current edition approved April 1, 2010. Published April 2010. Originally
2
approved in 1943. Last previous edition approved in 2008 as A262–02a (2008). The boldface numbers in parentheses refer to the list of references found at the
DOI: 10.1520/A0262-10. 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
...

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:A 262–93a Designation: A262 – 10
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 (ϵ) 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 PracticeE—Copper-–CopperSulfate-–SulfuricAcidTestforDetectingSusceptibilitytoIntergranularAttackinAustenitic
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
notbevisibleinthemicrostructure,canresultinhighcorrosionratesinboththenitricacidandferricsulfate-sulfuricacidsolutions.
1.3 Theoxalicacidetchtestisarapidmethodofidentifying,bysimpleetching,thosespecimensofcertainstainlesssteelgrades
whichthat 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%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-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 whichthat 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
These practices are under the jurisdiction of ASTM Committee A-1 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 Dec. 15, 1993. Published February 1994. Originally published as A 262–43T. Last previous edition A 262–93.
Current edition approved April 1, 2010. Published April 2010. Originally approved in 1943. Last previous edition approved in 2008 as A262 – 02a (2008). DOI:
10.1520/A0262-10.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
...