General Concepts of Stress-Corrosion Cracking

Some general rules for susceptibility to stress-corrosion cracking are presented. The inherent immunity of single elements but not of homogeneous alloys, the specificity of corrodents, and the effects of minor impurities or heat treatments are illustrated. Important electrochemical and metallurgical factors in stress-corrosion cracking are described, and the two principal theories outlined. The continuous electrochemical mechanism of cracking has serious drawbacks, and the periodic electrochemical-mechanical mechanism appears to be more generally applicable. The mechanical-fracture step in the latter mechanism has been described by a restricted-slip model, which predicts susceptibility only for those alloys which exhibit highly restricted slip and predicts immunity for metals in which cross slip is easy. Tests of this model to date with copper alloys and stainless steels are all confirmatory. 3.5.8, 3.7.3, 3.8.2, 3.7.4