Session: RIP: Predictive Modeling and Characterization of Corrosion Processes in Complex Environments (In Honor of Professor Digby Macdonald) (Part I of IV)
Localized Corrosion Damage Morphology of Carbon and Stainless Steel in Chloride-Contaminated Concrete (RIP2026-00081)
The mechanisms controlling the damage evolution of chloride-induced corrosion of carbon and stainless steels in concrete are still not well-understood. Models of damage distributions according to macrocell coupling suggest that SS corrosion is likely to remain more localized than CS but such models assume general corrosion over discrete regions of the steel surface and do not consider aspects of pitting corrosion that may define the initial stages of corrosion damage. This study examines 410 SS and CS in chloride-admixed concrete beams exposed for several years. The objective is to define how early and advanced corrosion features differ in SS and CS and to clarify what must be considered when studying localized corrosion of steel in concrete. Three-dimensional surface profilometry captured the morphology of pits and clusters, and local microcell measurements were used to inform possible rate limitations for SS corrosion. The results show that 410 SS corrosion stayed confined to localized regions even at chloride levels above reported thresholds. Autopsies found SS damage ranging from isolated pits to confined pit clusters, while CS damage ranged from isolated pits to wide cluster morphologies. EIS measurements showed a stronger repassivation tendency in SS. Local microcell measurements suggest that corrosion product morphology can greatly influence the progression of localized corrosion and therefore may need to be considered in damage evolution models.
