ICS 77.040.99<\/strong> This standard specifies the specimen, test solution, test equipment, test conditions and procedures, evaluation of test results, and test report for the 10% oxalic acid etch test method for stainless steels<\/strong>.<\/p>\n This standard is applicable as a screening test method<\/strong> for inspecting intergranular corrosion of austenitic stainless steels. After electrolytic etching of the specimen in 10% oxalic acid solution, the metallographic structure of the etched surface is observed under a microscope to determine whether long-term hot acid tests such as sulfuric acid-ferric sulfate, 65% nitric acid, nitric acid-hydrofluoric acid, and sulfuric acid-copper sulfate are required.<\/p>\n For ultra-low carbon steels (carbon content ≤ 0.03%) and stabilized steel grades (with titanium or niobium added), sensitization treatment regime is 650°C<\/strong>, holding for 2 hours for wrought specimens and 1 hour for castings, followed by air cooling.<\/p>\n Dissolve 100g<\/strong> of premium pure oxalic acid in 900 mL<\/strong> of distilled water or deionized water to prepare 10% oxalic acid solution<\/strong>.<\/p>\n
\nReleased:<\/strong> 2000-10-25
\nImplemented:<\/strong> 2001-09-01
\nIssued by:<\/strong> State Bureau of Quality and Technical Supervision<\/p>\n1. Scope<\/h3>\n
2. Normative References<\/h3>\n
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3. Specimen Sampling<\/h3>\n
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4. Sensitization Treatment<\/h3>\n
5. Test Solution<\/h3>\n
6. Test Conditions<\/h3>\n
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7. Structure Classification<\/h3>\n
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\n Category<\/th>\n Name<\/th>\n Characteristics<\/th>\n<\/tr>\n \n Class I<\/td>\n Step Structure<\/td>\n No corrosion grooves at grain boundaries<\/td>\n<\/tr>\n \n Class II<\/td>\n Mixed Structure<\/td>\n Corrosion grooves, no grains surrounded<\/td>\n<\/tr>\n \n Class III<\/td>\n Ditch Structure<\/td>\n Grains surrounded by corrosion grooves<\/td>\n<\/tr>\n \n Class IV<\/td>\n Free Ferrite Structure<\/td>\n No grooves, ferrite revealed<\/td>\n<\/tr>\n \n Class V<\/td>\n Continuous Ditch Structure<\/td>\n Deep, continuous corrosion grooves<\/td>\n<\/tr>\n \n Class VI<\/td>\n Pit Structure I<\/td>\n Many shallow pits, few deep pits<\/td>\n<\/tr>\n \n Class VII<\/td>\n Pit Structure II<\/td>\n Few shallow pits, many deep pits<\/td>\n<\/tr>\n<\/table>\n 8. Test Report Requirements<\/h3>\n