Effects of alloying on oxidation and dissolution corrosion of the surface of γ-Fe(111): a DFT study.

Effects of alloying elements in popular steels on the oxidation and dissolution corrosion of the surface of γ-Fe(111) have been investigated by performing density functional theory calculations within the local density approximation. First, the segregation of alloying atoms as well as preferential adsorption sites for oxygen and water were carefully examined, and it was found that all of the alloying elements considered had a tendency to segregate to the surface, and that the most preferred adsorption sites were the hexagonal closed packed (hcp) site and the top site for oxygen and water, respectively. The adsorption energies that characterized the tendency for oxygen or water to be adsorbed on the alloy surface showed that all ten alloying elements (especially Cr, Si, and Cu) were able to inhibit the adsorption of oxygen, and that all of the alloying elements except for Nb, Mo, and Ti inhibited water adsorption. The electrode potentials, which indicate the electrochemical stabilities of the surfaces of the alloys, suggested that all of these alloying elements (especially Cr, Mo, and Si) were able to suppress the adsorption of oxygen and water on the investigated surfaces, except for Nb and Ti in the case of water adsorption. Density of states analysis further indicated that all ten alloying elements (especially Cr, Si, Mo, and Cu) enhanced the corrosion resistance of the fcc Fe substrate, except for Nb and Ti with respect to dissolution corrosion.