The Influence of Copper on the Corrosion Resistance of CoCrMo-xCu Alloy in Several Biological Solutions for Biomedical Applications

CoCrMo alloys are widely used as orthopedic and dental implants, owing to their superior mechanical properties, wear resistance, and biocompatibility. Copper (Cu) ion exhibits strong antibacterial activity, making it a promising alloying element. A systematic study was conducted on the corrosion resistance and ion release behavior of CoCrMo-xCu (Co-xCu) alloys in both as-cast and heat-treated states in different simulated solutions. The results indicated that the corrosion resistance of Co-xCu alloys decreased with the increasing Cu content, which was mainly attributed to the formation of micro-galvanic couples between the alloy matrix and Cu-rich phases. The synergistic effect of heat treatment and an appropriate Cu content can effectively improve the corrosion resistance of the alloys, and the corrosion current density (icorr) of Cu-containing cobalt alloys was comparable to that of Cu-free cobalt alloys. Maximum concentrations of Co, Cr, and Cu ions released from Co-xCu alloys were lower than the corresponding recommended safety limits. Through the combined optimization of Cu content and heat treatment, the metal ion release levels of Cu-containing cobalt alloys can be reduced to values even lower than those of Cu-free cobalt alloys.