Passive films and corrosion resistance of Ti-Hf alloys in 5% HCl solution

Ti-Hf alloys with Hf contents of 10, 20, 30, and 40 mass% were prepared by a tri-arc furnace and homogenized at 1273 K for 21.6 ks, and then these alloys were cold rolled into 3-mm-thick plates. The alloy specimens were subjected to a solution treatment in a vacuum at 1223 K for 3.6 ks and then rapidly quenched in ice water before corrosion tests. The corrosion resistance of these alloys was investigated by studying the anodic polarization curves at 310 K in 5% HCl solution to determine the potential use of these alloys in biomedical applications. The passive films formed on the surfaces of the alloys were examined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The results reveal that all the Ti-Hf alloys exhibit a passive behavior in 5% HCl solution, which is attributed to the passive film formation of a mixture of both HfO₂ and TiO₂. The corrosion resistance of the Ti-Hf alloys gently increases with the Hf content and the Ti-Hf alloys exhibit better corrosion resistance than commercial pure (CP) Ti-the currently-used metallic biomaterial.