Co-adsorption of O and Cl on Ti(0 0 0 1) surface: A microscopic study by DFT and AIMD

The co-adsorption mechanism of O and Cl on Ti surface under marine condition at the atomic scale is crucial, but remains unclear. In the present work, the co-corrosion model of O and Cl on Ti surface under O-rich and Cl-rich conditions was successfully established to study the dynamical diffusion behavior, adsorption process and atomic bonding interaction of O and Cl in pre-oxidized Ti and NaCl coated or deposited Ti by using the density functional theory and ab initio molecular dynamics method. The present adsorption results are consistent with the observed experimental phenomena. More atomic details and the bonding interaction between Cl, O and Ti during the co-corrosion process are revealed to promote understanding of the puzzles about active oxidation. It is found that, both O and Cl tend to adsorb on the surface of the oxide, and Cl diffuses more easily than O. Cl can adsorb on the top Ti atom, pull Ti from the surface to form vacancy and promote the internal oxidation. In addition, O penetrates into the inner layer more easily than Cl. O can improve the Cl-Ti surface reactivity by diffusing inward through the hcp site to form a thick and porous corrosion layer with a large number of defects. Further, several feasible ways for improving the corrosion resistance under salt spray condition are recommended for the design of novel anti-corrosion metals or alloys.