Reactive molecular dynamics simulations of the initial oxidation and passivation of Fe-Cr alloy steel

This investigation employed reactive molecular dynamics (ReaxFF-MD) simulations to study nano scale passivation behavior of Fe-Cr alloys in highly alkaline environments. The impact of external electric field strength, temperature, and chromium content on the formation and development of the passive film was revealed, integrating kinetic and thermodynamic analyses to provide a comprehensive understanding. The findings indicate that the application of an electric field markedly accelerated the growth of the passive layer, with charge transfer and ion migration processes being directly modulated by the field. Additionally, variations in temperature induced staged changes in the passivation rate, thereby illuminating the thermodynamic effects on the rates of chemical reactions. Furthermore, increasing the chromium content resulted in a denser and more stable passive film. Chromium in the oxidation state of Cr3+ plays a pivotal role in enhancing the stability and density of the passive layer due to its more stable oxidative state.