Active Corrosion Rate for Ti-based Alloys in Aqueous Corrosion and Its Correlation with the Bond Order Obtained by Electron Theory

Abstract

In order to understand alloying effects on the corrosion resistance of titanium, polarization curve were measured at 343 K in both 10 mass% HCl and 10 mass% H₂SO₄ solutions with various Ti-M binary alloys (M=Al, Nb, Ta, Zr, Hf, Fe, V, Cr, Mo, Co and Ni). The results were interpreted by using the bond order (Bo) obtained by a moleculr orbital calculation. The bond order (Bo) is a measure of the strength of the covalent bond between titanium and alloying elements. It was found that alloys containing the elements with higher Bo values showed the lower critical anodic current density in the polarization curve and hence the higher corrosion resistance. It is likely that the Bo is a convenient parameter for describing the corrosion rate of titanium alloys in acid environments such as HCl and H₂SO₄ solution.