Quantum-Chemistry Based Studying of Rebar Passivation in Alkaline Concrete Environment

A clear understanding of the mechanisms of passivation and depassivation of steel surface is critical to the effective control of rebar corrosion. The process of passivation involves oxidation of iron atoms in the typical concrete environment. Traditional electrochemical approach of interpreting steel corrosion follows the changes in voltage and current as a result of electrode reactions, therefore is incapable of depicting iron oxidation and the incurred structural change at the atomic scale. A research study was conducted recently to simulate the passivation process of steel using a Quantum Chemistry-based reactive force field. The initiation and growth of oxides were found to be highly dependent on the thermodynamics and availability of reactants. Three oxidation stages were identified until a highdensity triplex structure was formed on iron surface, after which the oxidation of iron progressed at a significantly reduced speed. Results from this study will benefit improving the knowledge base and controlling of rebar corrosion.