Comparison of in vitro corrosion behaviour and biocompatibility of Ti-13Zr-13Nb and passivated 316L stainless steel coated with TiCN

Abstract

AISI 316L stainless steel finds widespread use as implant materials. However, it is prone to localized attack in the body fluids. Titanium alloys have the highest corrosion resistance among the metallic materials used as orthopaedic prostheses. Therefore, an implant material that unites the high surface stability of titanium alloys and the low cost of the 316L is of great interest. TiCN films obtained by PVD processes present high wear and corrosion resistances making them attractive materials for orthopaedic applications. However, there is little information about the corrosion behaviour of TiCN-coated stainless steels in physiological solutions. In this study, 316L specimens were passivated in nitric acid solution for 10 minutes and then coated with TiCN films produced by PVD process. The corrosion resistance of the coated specimens was evaluated by Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization tests after 28 days of immersion in Hanks' solution. The results were compared with those obtained from bare, passivated, non passivated and TiCN-coated 316L steel, and bare Ti-13Zr-13Nb specimens. The passivated and TiCN-coated 316L specimens presented corrosion resistance similar to that of bare 316L. The highest corrosion resistance was obtained for Ti-13Zr-13Nb specimens. The in vitro biocompatibility of Ti-13Zr-13Nb and TiCN-coated 316L was investigated using a citotoxicity assay. Both materials were not cytotoxic in the conditions tested.