stresscorrosion

Stress corrosion, or stress corrosion cracking (SCC), is the growth of cracks in a material caused by the combined action of a corrosive environment and applied or residual tensile stress. Cracks can initiate at flaws or inclusions and may propagate subcritically, often with little plastic deformation, eventually leading to sudden and unexpected failure. SCC is distinguished from uniform corrosion by its localized, environment-sensitive cracking behavior.

Two broad mechanisms are commonly invoked. In anodic dissolution, the crack tip chemistry drives localized metal dissolution under tensile stress, sustaining crack advance. In hydrogen-assisted cracking, mechanical stress promotes entry or pre-existing hydrogen, which weakens cohesive bonds and accelerates crack growth. Some systems involve a combination of these processes. The exact mechanism often depends on material, environment, temperature, and stress state.

Key factors include the corrosive species present (such as chloride ions, sulfides, or caustic/alkaline media), temperature, pH, and the magnitude and nature of the applied or residual stress. Material properties—composition, microstructure, heat treatment, and presence of sensitization or surface films—also strongly influence susceptibility. Design features, manufacturing processes, and service history (like welding and residual stress) affect SCC risk.

Commonly affected materials and environments include stainless steels and nickel alloys in chlorides (chloride-induced SCC), aluminum alloys and high-strength steels in various aggressive media, and components in petrochemical or nuclear industries where hydrogen embrittlement and high-temperature water chemistry can play roles. Prevention focuses on reducing tensile stress, selecting more resistant materials, controlling the environment (inhibitors, pH, temperature), applying protective coatings, and employing proper fabrication practices to minimize residual stresses and sensitization.