A Dislocation-Theory Explanation of Intergranular Corrosion and Intergranular Stress-Corrosion Cracking in Mild Steels

By grain-boundary segregation, gradients of the metalloid concentration in mild steels are generated. The accompanying elastic strains favour the incorporation of extrinsic grain-boundary dislocations. These assist the diffusion of the corrosive medium along the grain boundaries (intergranular corrosion) and, under mechanical stress, emit glide dislocations which produce grain-boundary slip steps showing enhanced dissolution (intergranular stress-corrosion cracking).