A sputter-deposited Ti-20at%W alloy was anodized in order to determine the effect of alloy species upon the structures of anodic films on Ti. It was of interest that an amorphous oxide film developed on the alloy at voltages of up to about 200V. Such film formation, on relatively pure Ti, occurred at voltages of less than 20V. The amorphous films consisted of an outer TiO2 layer, and an inner layer which contained TiO2 and WO3. The layered films formed due to the migration of Ti4+ ions at a rate which was about 2.4 times higher than that of W6+ ions. This was attributed to the relative strengths of W6+-O and Ti4+-O bonds. Film growth proceeded via the migration of both O2- and/or OH- ions and metal cations. This was typical of amorphous anodic films, with the transport number of cations being determined, using a Si species marker, to be 0.39.

Influence of Tungsten Species on the Structure of Anodic Titania.  Habazaki, H., Takahiro, K., Yamaguchi, S., Shimizu, K., Skeldon, P., Thompson, G.E., Wood, G.C.: Philosophical Magazine A, 1998, 78[1], 171-87