Long-term corrosion performances and cytocompatibility of nitrided Ti and Ti-6Al-4V alloy in severe functional conditions

In the present work, nitrogen ion implantation (original method) to enhance the corrosion performance and cytocompatibility of biomedical pure titanium (CP Ti) and Ti-6Al-4V alloy has been studied. Different characterization methods were used to investigate the corrosion resistance of the nitrided Ti and Ti-6Al-4V samples such as anodic polarization, electrochemical impedance spectroscopy, monitoring of the open circuit potentials and corresponding gradients, evaluation of corrosion rates. Further, cell viability, initial cell spreading and osteoblast proliferation were tested in order to assess cytocompatibility of modified Ti and Ti-6Al-4V alloy. In severe functional conditions, the main electrochemical parameters for nitrided biomaterials presented better values, revealing nobler behaviour than un-nitrided samples; these more favourable values assure a very good corrosion resistance for long term of the treated biomaterials. The results of biological performance evaluation indicated that nitrided Ti and Ti-6Al-4V represent suitable biomaterials for the adhesion and proliferation of human osteoblasts in vitro. All these findings demonstrate that nitrided biomaterials exhibited a very good improvement of their corrosion resistance and biocompatibility, characteristics which recommend them as potential candidates for bone implants.