Abstract
For detecting susceptibility to intergranular corrosion (IGC) in austenitic stainless steels, ASTM Recommended Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (A 262), Practice A (metallographic test), serves as a screening test. Alloys showing “step” or “dual” structures are considered to have passed the test. When a “ditch” structure is obtained, the material needs further testing by one of the immersion tests (Practices B, C, D, or E). It has been observed that the electro-etching parameters of Practice A are rather severe, leading to the development of “ditch” structures in nonsensitized materials which are not susceptible to IGC. A modified etching technique has been developed in which nonsensitized samples of Type 316 stainless steel as detected by Practice E show step structure or no structure at all; ditch structure is developed only in the cases of samples heat treated close to or within the sensitization range. Use of this technique could result in a reduction of the number of specimens that must be tested by one of the other practices in ASTM A 262.
