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This document describes a method to test for IGC in austenitic stainless steels using an oxalic acid etch. This method can evaluate non-sensitization of austenitic stainless steels by observing the structure of the etched surface with a microscope after performing electrolytic etching (hereinafter called "etching") on austenitic stainless steel in an oxalic acid solution. This method can evaluate suspicions of sensitization of austenitic stainless steels, because it does not etch chromium depletion adjacent to the chromium-rich grain boundary precipitates but chromium-rich grain boundary carbides themselves. If sensitization is suspected, the ferric sulfate-sulfuric acid test (ISO3651-2), 65 % nitric acid test (ISO3651-1), copper sulfate-sulfuric acid test (ISO3651-2), or EPR test (ISO12732) should be conducted to evaluate sensitization of austenitic stainless steels.