Corrosion Initiation in Reinforced Concrete: Evaluating the Critical Chloride Thresholds for Stainless Steels Under Accelerated Ion Migration

Reinforced-concrete structures in aggressive environments may not always achieve their intended service life. To enhance durability in such cases, stainless steel reinforcement can be a suitable alternative, contributing to more sustainable and resilient infrastructure. This paper presents the findings of an experimental study aimed at evaluating the critical chloride threshold in concrete under accelerated chloride migration conditions for carbon steel and two types of stainless steel reinforcement: EN 1.4003 (AISI S40977) and EN 1.4482 (AISI S32001). Electrochemical measurements were used to determine critical chloride threshold distributions, which were subsequently incorporated into a probabilistic case-study assessment of corrosion initiation using Monte Carlo simulation. The results showed substantially higher chloride threshold values for stainless steel reinforcement than for carbon steel. Under the assumptions adopted in the case study, including a constant diffusion coefficient, the estimated corrosion initiation period corresponding to a 10% probability of corrosion was approximately 7.5 years for carbon steel and more than 100 years for EN 1.4482 stainless steel. The proposed methodology provides a probabilistic framework for evaluating the influence of reinforcement type on corrosion initiation and can support both the assessment of existing structures and the durability-based design of new reinforced-concrete structures exposed to chloride-containing environments.