Localized corrosion damage evolution of steel reinforcement in chloride-contaminated concrete

Abstract

This study investigates the spatiotemporal evolution of localized corrosion activity and its progression using spatially resolved electrochemical monitoring, sequential autopsies, and high-resolution optical profilometry in reinforced concrete beams with localized chloride contamination and mortar cylinders with admixed chloride. Both carbon steel and stainless steel reinforcements were evaluated to capture material-dependent behavior. Results demonstrate that chloride-threshold exceedance alone is not an immediate predictor of damage extent, morphology, or severity. Instead, damage accumulation is governed by the persistence and expansion of localized corrosion activity. Stainless steel exhibits delayed and spatially restricted corrosion characterized by indications of activation-repassivation cycles, while carbon steel shows early, persistent, and spatially extending corrosion leading to greater cumulative damage. Across both materials, damage is dominated by a distribution of localized features, where numerous shallow damage features coexist with a small fraction of deep localized damage regions. These findings challenge conventional propagation models based on uniform corrosion rates or fixed pitting factors and highlight the need to distinguish between activation, persistence, and repassivation of localized corrosion. A mechanistic framework is proposed in which the chloride threshold is treated as an indicator of the possibility for localized corrosion and damage is represented as an evolving population of localized features that grow in number, size, and spatial extent. This approach is expected to provide a more physically consistent basis for predicting damage evolution and maximum penetration in reinforced concrete systems.