ASTM A262 Standard Practices for Determining Susceptibility to Intergranular Attack in Austenitic Stainless Steels

ASTM Tests

ASTM A262 Standard Practices for Determining Susceptibility to Intergranular Attack in Austenitic Stainless Steels

This specification covers standard practices for detecting susceptibility to intergranular attack in austenitic stainless steels.

ASTM A262 Standard Practices for Determining Susceptibility to Intergranular Attack in Austenitic Stainless Steels

This standard covers the following five tests;

  • Oxalic Acid Abrasion Test for Classification of Abrasion Structures of Austenitic Stainless Steels
  • Sulfuric Acid Test for Determination of Susceptibility to Intergranular Attack in Ferric Sulphate Austenitic Stainless Steels
  • Nitric Acid Test for Determination of Susceptibility to Intergranular Attack in Austenitic Stainless Steels
  • Copper – Copper Sulphate – Sulfuric Acid Test for Determination of Susceptibility to Intergranular Attack in Austenitic Stainless Steels
  • 50% Sulfuric Acid Test for Determination of Susceptibility to Intergranular Attack in Copper – Copper Sulphate – Molybdenum Bearing Austenitic Stainless Steels


ASTM A262 Application Method

  • Susceptibility to intergranular attack associated with precipitation of chromium carbides is readily detected in all six tests.
  • In forged chromium-nickel-molybdenum steels, the Sigma phase, visible or invisible in the microstructure, can cause high corrosion rates in nitric acid alone.
  • Sigma phase in microstructure visible or invisible titanium or columbium stabilized alloys and cast molybdenum-containing stainless alloys can cause high corrosion rates in both nitric acid and ferric sulfate-sulfuric acid solutions.
  • The oxalic acid etching test is a rapid method of identifying, by simple etching, samples of certain stainless steel grades that are essentially insensitive to intergranular attack associated with chromium carbide precipitates. These samples will have low corrosion rates in certain corrosion tests and can therefore be accepted (eliminated) from the test.
  • The ferric sulfate - sulfuric acid test, copper - copper sulfate - 50% sulfuric acid test, and the nitric acid test are based on weight loss determinations and therefore provide a quantitative measure of the relative performance of the samples under consideration. In contrast, the copper - copper sulfate - 16% sulfuric acid test relies on visual inspection of bending specimens and therefore classifies specimens as either acceptable or unacceptable only.
  • In most cases, the 15-hour copper – copper sulfate – 16% sulfuric acid test or the 120 hour ferrous sulphate – sulfuric acid test together with the oxalic acid abrasion test will provide the necessary information as soon as possible. 
  • The 240 hour nitric acid test should be applied to stabilized and molybdenum-containing grades intended for use in nitric acid and all stainless steel grades that may be subject to end grain corrosion in nitric acid service.

This standard does not purport to address all, if any, security issues associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices prior to use and to determine the applicability of regulatory restrictions.


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