Influence of nitrogen addition on the crevice corrosion resistance of nitrogen-bearing austenitic stainless steels

Crevice corrosion studies were carried out on nitrogen-bearing types 304, 3 16 and 317 austenitic stainless steels (SS) by a potentiodynamic anodic pol arisation method in an acidic chloride medium. A special all-glass crevice assembly was used for providing reproducible crevice effects on the surface of the test specimen. The results indicated that the increase in nitrogen content improved the crevice corrosion resistance of the alloys by decreasi ng the active dissolution, and increasing both passive film stability and t he potential at which crevice attack was stable. This was very significant for 304 and 316 SS alloys in comparison with 317 SS alloys. The combined in fluence of nitrogen and molybdenum was found to be very significant in prov iding high crevice corrosion resistance for 317 SS alloys. Optical microsco pic observation revealed severe crevice attack on types 304 and 316 SS allo ys compared to mild crevice attack on type 317 alloys. Based on the results of the present investigation a possible mechanism by which nitrogen additi on improved the crevice corrosion resistance is discussed. (C) 2000 Kluwer Academic Publishers.