Atomistic simulation of initial stages of iron corrosion in pure water using reactive molecular dynamics

Reactive Force Field Molecular Dynamics (ReaxFF-MD) was used to study the initial stages of iron corrosion in pure water. The simulations were performed on iron under various applied external electric fields and temperatures. Oxide film formation was accompanied by iron dissolution in water, indicating active corrosion and supporting the expected thermodynamic behavior of iron in pure water. Oxide film thickness and iron dissolution increased with increasing applied external electric field. Corrosion rates increased slightly with increasing temperature within the temperature range of this investigation (300–350 K). Critical stages of the iron corrosion process during the simulations were identified as dissociation of water to OH− and H+, adsorption of OH− on the iron surface, penetration of oxygen into iron to form iron oxides, and dissolution of iron into solution. Comparisons of the simulated charge distributions and pair distribution functions to those of reference oxides showed the formed oxide compositions were not pure phases, but rather a mixture of oxides.