Structure, hydrophilicity and corrosion resistance of sol–gel derived Ag-containing TiO₂ film on plasma nitrided 316L stainless steel

Pure and Ag-containing TiO₂ films (Ag/Ti = 3.3 at.%) are coated on plasma nitrided 316L stainless steel by sol–gel method for biomedical applications. The addition of Ag does not cause obvious change in TG–DSC curves of the dried gels. The rough surface generated by plasma nitriding and the addition of Ag improve structural integrity of the TiO₂ films. X-ray diffraction reveals N loss and oxidation of the nitride layer during calcination treatment, and peaks of Ag or its oxides are not detected. X-ray photoelectron spectroscopy analysis indicates that Ag presents as metallic state in the film. Water contact angles of the coating samples decrease with UV irradiation treatment. The potentiodynamic polarization tests in a Ca-free Hank’s balanced salt solution show that the TiO₂ coated samples have decreased corrosion resistance due to N loss and oxidation of the nitride layer. The methods for crystallization of TiO₂ gel layers with minimized or avoided structural changes of the nitride layer will be tried in order to improve corrosion resistance of the duplex treated 316L stainless steel.