Electrochemical influences in fracture initiation

Dissolution at metal surfaces may be structurally or non-structurally dependent. The effects of grain boundaries, interfaces between discrete phases, non-metallic inclusions, and slip lines in promoting structurally dependent attack are considered in the context of a variety of metal-environment systems. Pitting and fissuring, as examples of non-structurally dependent attack, but as precursors to cracking, are also considered, as well as hydrogen derived from corrosion reactions. The effects of geometrical discontinuities, such as pits, fissures, or cracks, may be important as sites for electrochemical change, quite apart from their influences on stress intensification. Finally, consideration is given to the question of why stress-corrosion cracking environments are so specific, in comparison with those that promote corrosion fatigue.