A phenomenological model for the chloride threshold of pitting corrosion of steel in simulated concrete pore solutions

Purpose - This work seeks to present a systematic study that aimed to provide quantitative understanding of the fundamental factors that influence the chloride threshold of pitting corrosion of steel in concrete, by conducting a set of laboratory tests to assess the corrosion potential (E-corr) and pitting potential (E-pit) of steel coupons in simulated concrete pore solutions. Design/methodology/approach - With the aid of artificial neural network, the laboratory data were used to establish a phenomenological model correlating the influential factors (total chloride concentration, chloride binding, solution pH, and dissolved oxygen (DO) concentration) with the pitting risk (characterized by E-corr - E-pit). Three-dimensional response surfaces were then constructed to illustrate such predicted correlations and to shed light on the complex interactions between various influential factors. Findings - The results indicate that the threshold [Cl-]/[OH-] of steel rebar in simulated concrete pore solutions is a function of DO concentration, pH and chloride binding, instead of a unique value. Research limitations/implications - The limitations and implications of the research findings were also discussed. Practical implications - This research could have significant practical implications in predicting the service life of new or existing reinforced concrete in chloride-laden environments. Originality/value - This study further advances the knowledge base relevant to the chloride-induced corrosion of steel rebar in concrete.