Corrosion behaviour of a beta-titanium alloy.

The beta-titanium alloy, a particular type of titanium, has been investigated as a biomaterial because of its good mechanical performances and its high corrosion resistance and biocompatibility. This work focuses on the corrosion performance of a beta-titanium alloy of composition Ti-11Mo-2V-4Nb-3Al in Hank's physiological solution. Potentiodynamic tests were performed from -0.25 V to 3.5 V; the breakdown potential was not reached. To observe the behaviour of the alloy while submitted to long-term aggressive conditions, 1, 4 and 8 cycles of cyclic polarization were carried out. Results show a high resistance of the alloy to corrosion and a stabilization of the surface after several corrosion cycles. Pitting was not observed and a fast ability of the surface to repassivate was noticed. The surface was characterized by different techniques before and after corrosion testing. Following the corrosion tests, X-ray Photoelectron Spectroscopy (XPS) showed the presence of calcium and phosphorus, an increase of the oxide layer was measured by Auger Electron Spectroscopy (AES), a relatively smooth surface was visualised by Scanning Electron Microscopy (SEM) and contact-angle measurements showed that the surface energy increased.