Mechanistic insights into early stages of iron corrosion under electrochemical conditions: A DFT study

Iron corrosion is a persistent issue across a wide range of industries, leading to both economic setbacks and safety concerns. This process is driven by electrochemical reactions that occur when the metal interacts with its surrounding environment. However, the complexity of electrochemical interfaces hinders good understanding for corrosion behaviour at the atomic scale. In this work, we employed grand canonical density functional theory (GC-DFT) along with a hybrid explicit and implicit solvation model to study the interactions between iron surface and its primary corrosive species, water and oxygen. The simulations revealed that the water molecules at the interface adopt specific orientations to achieve the optimal interactions with the surface. The GC-DFT simulations further revealed that the adsorption of water molecules strengthens at positive potentials, whereas atomic oxygen adsorption weakens under the same conditions. Moreover, water dissociation, the key step in iron corrosion, is found to be catalysed by the oxygens adsorbed on the O-bridge sites of the Fe(100) surface. The findings offer valuable insights into the initial stage electrochemical behaviour of water and oxygen on iron surfaces, contributing to a better understanding and prevention of iron corrosion.