Electrochemical behavior, passive film characterization and in vitro biocompatibility of Ti–Zr–Nb medium-entropy alloys

Ti–Zr–Nb medium-entropy alloys (TiZrNb, Ti40Zr40Nb20, Ti45Zr35Nb20, Ti45Zr45Nb10 and Ti50Zr40Nb10 MEAs) have the potential to be bone implants for their appropriate yield strength and elastic modulus. In this study, their electrochemical behavior, passive film characterization and in vitro biocompatibility were investigated, compared with pure metals of Ti, Zr and Nb. Electrochemical potentiodynamic polarization shows corrosion current densities of Ti–Zr–Nb MEAs in PBS solution varied from 6.243 × 10 –7 to 3.259 × 10 –7 A/cm 2 with the increasing Zr content. Their passive films consisted of TiO 2 , ZrO 2 and Nb 2 O 5 , identified by XPS, Ti and Nb which enriched the whole film due to their higher migration rate during the oxidation. The films could be subdivided into barrier and outer layer, and the corrosion resistance of the former was better than that of the latter in PBS solution. And in vitro test exhibited all Ti–Zr–Nb MEAs possessing equivalent biocompatibility compared with pure metals of Ti and Zr.