From Passivity Breakdown to Brittle Failure: Stress Corrosion Cracking in Prestressed Concrete—A Review

Stress corrosion cracking (SCC) of prestressing steel threatens prestressed concrete structures with sudden, brittle failure and minimal visible warning. While mechanical stress, localized corrosion, and hydrogen uptake are recognized drivers, the mechanisms connecting sulfide exposure in cementitious materials to hydrogen uptake and crack initiation at the steel–concrete interface remain poorly understood. This review synthesizes the coupled electrochemical, mechanical, metallurgical, and environmental processes governing SCC, with particular emphasis on the interactions of sulfide species with chloride ingress, carbonation, pitting, and hydrogen-assisted cracking under sustained tensile stress. Evidence indicates that sulfides weaken passive-film protectiveness and facilitate hydrogen entry, while localized corrosion and acidification create favorable conditions for crack initiation and propagation. Because SCC susceptibility emerges from the combined effects of environmental exposure, steel microstructure, and mechanical loading, isolated environmental parameters cannot adequately predict risk. Accelerated laboratory tests offer comparative insight but have limited representativeness of the complex conditions of prestressed concrete. A critical gap persists: no quantitative relationship has yet been established between cement sulfide content, sulfide availability at the steel surface, hydrogen uptake, and actual SCC susceptibility. Bridging this gap requires service-representative experiments on stressed prestressing steel embedded in mortar or concrete to develop reliable durability criteria and move beyond precautionary regulatory limits.