A Review of the Governing Factors in Pit-to-Crack Transitions of Metallic Structures

Through a combination of mechanical stresses and corrosive environments, a material's performance may be hindered by the complex evolution of damage due to stress corrosion cracking (SCC) or corrosion fatigue (CF). Understanding the contribution of the localized corrosion features, loading state, crack-formation features, local microstructure, and environment remains a critical issue when predicting crack initiation and propagation leading to potential metal failure. As such, the lifetimes of many exposed alloys are greatly reduced by the presence of corrosion damage and the prediction of this deleterious influence via standard fracture mechanics methods is nontrivial. Current knowledge is insufficient to fully address governing features and mechanism of the pit-to-crack transition, a common initiation mode of SCC and CF. This review examines current research of pit-to-crack transitions for various alloys and loading conditions and highlights critical areas of research necessary for informing the mechanism related to a material's lifetime in a stressed corrosive environment.