ASTM A262-10

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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.
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