Electronic theoretical study on the corrosion and passivation mechanism of Ti metal

The atomic cluster models of the crack in αTi formed by dislocation accumulation were set up. The electronic structure of Ti was calculated by using recursion method, and the influence of O, Cl, and Pd on the electronic structure of Ti was studied. The calculated results show that, the total density of states near Fermi level is lowerd due to the existence of O, which leads to the decrease of the chemical activity of Ti. The binding energy of Ti is reduced by oxygen. The affinity between O and Ti is large, so O is easy to react with Ti to form the oxide film. The stability of Cl in Ti and the affinity with Ti are not as good as O. Cl is difficult to substitute the O atom on the surface of Ti, so the oxide film of Ti is very stable, the phenomenon of over passivation can not occur. The environment-sensitive embedding energy of Pd in the crack is smaller than in αTi grain, so Pd is easy to diffuse to the crack and makes the environment sensitive embedding energy of H rise obviously, which leads to the weakening of H diffusion to the crack and the improvement of the stress-corrosion resistance of Ti.