Surface mobility mechanism of stress-corrosion cracking

The surface mobility stress-corrosion cracking mechanism is based on the assumption that environmentally induced crack propagation is due to the capture of vacancies by the stressed lattice, at the tip of the crack. The present paper shows that the role of the environment is not only to change the surface self-diffusivity of the metal or alloy, but also to supply the metal surface with the vacancies consumed by the crack propagation process. The achievements, advantages and limitations of the mechanism are discussed, and compared with the limitations found in other alternative mechanisms. Special attention is given to the principles involved in the anodic dissolution based mechanisms.