THE SURFACE CHARACTERIZATION OF TITANIUM AND TITANIUM-NICKEL ALLOYS IN SULFURIC-ACID

Passive films formed on pure Ti and crystalline and amorphous Ti-Ni alloys containing from 30 to 60 at% Ti in a sulfuric acid solution were studied by XPS and photoelectrochemical methods. The photocurrent increased with applied anodic potential. The band-gap energies in the surface films were in the range of 3.2-3.4 eV which decreased with increasing applied potential. In the surface film, Ti ions were enriched. The Ti in the film consisted of Ti4+, Ti3+ and Ti2- ions. The ratios between them on a specimen were independent of the applied potential, although the thickness of the surface film itself increased with the increasing potential. The surface films on pure Ti and Ti-Ni alloys contained OH-type oxygen.