Volume 4, Issue 6 (November 1976)
Evaluation of Intergranular Corrosion in Stainless Steel
Specimens of Type 304 austenitic stainless steel with carbon contents of 0.017, 0.024, 0.046, and 0.059% were subjected to intergranular corrosion tests in acidified copper sulfate solutions with and without additions of metallic copper. In the annealed condition the steels were not attacked by either of the test environments. After a sensitizing heat treatment, both test procedures showed essentially the same behavior; intergranular corrosion occurred only on steels with 0.046 and 0.059% carbon.
Of the visual, metallographic, and scanning electron microscope methods of examining test specimens, the latter produces a superior permanent record. Tactile examination proved to be a simple method of determining intergranular attack on specimens bent after exposure to the test solutions. Evaluation of the examination methods led to a proposed sequence for examining specimens, from a low-sensitivity visual examination to a high-sensitivity examination with a scanning electron microscope. Limitations of the test methods are discussed.