Unveiling the intricacies of steel corrosion induced by chloride: Insights from reactive molecular dynamics simulation

Corrosion of reinforcing steels induced by chloride has long been a focal point of research, yet the atomic behavior and mechanism is not fully understood. In present study, we developed a reactive force field (ReaxFF) incorporating the Fe/Cl system based on Density Functional Theory calculations to elucidate atomic-scale behavior and mechanism underlying chloride-induced corrosion of reinforcing steel. Results from ReaxFF simulations employing this force field indicate that the initiation of steel corrosion is catalytically induced by chloride present in the outer layer, and the electron transfer between atoms is identified as a critical factor in corrosion. Specifically, Fe atoms become positively charged, detaching from the matrix surface and dissolving into the solution to form iron chloride compounds with surface Cl, while oxygen atoms turn negatively charged, progressively infiltrating the matrix and combining with Fe to create intricate iron oxide compounds. Furthermore, the entire dynamic process of corrosion oxidation on the surface of the ferritic matrix and the formation of product species has been fully captured. This ongoing corrosion process leads to significant matrix loss from metal surface and a reduction in structural integrity.