Corrosion resistance of anodized Ti-6Al-4V alloy

In this study, titanium alloy Ti-6Al-4V sheet and rod were anodized at different applied potentials from 10-50V producing a range of colors such as light blue, dark blue, purple, and gold. Anodic polarization and an electrochemical impedance spectroscopy (EIS) technique were performed to investigate their corrosion resistance in saline and in Hank' solutions, respectively. The anodic polarization method was applied to study corrosion behavior where as the EIS technique was adopted to determine an oxide surface model, a thickness of the oxide layer, and to study corrosion resistance of specimens at longer immersion time (1, 24, 72, and 168h) in the testing solution. Hank' solution was kept at 37oC during the immersion testing in order to simulate an environment inside the human's body. The corrosion resistance of anodized Ti-6Al-4V alloy showed a clear improvement but reduced after soaking time was increased. Two layers of oxide films were found on the surface of anodized specimens, consisting of a porous outer layer and a dense inner layer. The thickest inner layer of 140nm was achieved from specimen anodized at 25V.