Corrosion behavior of new ternary zirconium alloys as alternative materials for biomedical applications

The in vitro corrosion behavior of four Zr-based alloys (Zr97.5Nb1.5VM1.0; VM = valve metal: Ti, Mo, W, Ta; at%) to be used as implant materials has been assessed and compared with that of Grade 2 Ti, which is known to be a highly compatible metal standard. Corrosion resistance was investigated by open circuit potential and electrochemical impedance spectroscopy (EIS) measurements, as a function of exposure time to an artificial physiological environment (Ringer's solution). Open circuit potential values indicated that Zr-based alloys and Grade 2 Ti undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the simulated aggressive environment. It also indicated that the tendency for the formation of a spontaneous oxide is greater for the Zr97.5Nb1.5Ta1.0 alloy and that this oxide has better corrosion protection characteristics than the ones formed on Grade 2 Ti or on Zr97.5Nb1.5Ti1.0, Zr97.5Nb1.5Mo1.0, and Zr97.5Nb1.5W1.0 alloys. EIS study showed high impedance values for all samples, increasing with exposure time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The fit obtained suggests a single passive film present on the metals surface, improving their resistance with exposure time, presenting the highest values to the Zr97.5Nb1.5Ta1.0 alloy. All these electrochemical results suggest that Zr97.5Nb1.5VM1.0 alloys are promising materials for osteo-synthesis prosthetic devices, since corrosion stability is directly associated with biocompatibility and is a necessary condition for applying a material as biomaterial