Sol-gel preparation, corrosion resistance and hydrophilicity of Ta-containing TiO2 films on Ti6Al4V alloy

Ta-containing TiO2 films with Ta contents of 5%, 20%, 33% (mole fraction) were Sol-gel coated on the surface roughened Ti6Al4V alloy by dip coating method for biomedical applications. The Ta-TiO2 films on 1.5 mol/L NaOH-HCl pretreated substrate are adherent, but there are cracks for the sample with 33% Ta. X-ray photoelectron spectroscopy results show that Ti and Ta exist as TiO2 and Ta2O5 in the film, and Al element is not detectable. X-ray diffraction and Raman scattering analyses reveal that the addition of Ta decreases crystallization of the films. Potentiodynamic polarization test in a Ca-free Hank's balanced solution demonstrates that the coating samples markedly improve the corrosion resistance compared with the polished sample. The addition of Ta impedes UV light-induced hydrophilic conversion of the coating samples. The sample with 20% Ta has enough film integrity and hydrophilic conversion rate, and is expected to possess good biological properties.