A metal ion release study of CoCrMo exposed to corrosion and tribocorrosion conditions in simulated body fluids

This work has investigated the metal ion release of a low carbon CoCrMo subjected to different electrochemical and tribocorrosion conditions in NaCl, phosphate buffer solution (PBS) and PBS with protein (albumin) at the human body conditions of 37 °C. Cobalt is the most concentrated ion and has the largest concentration ratio in all testing conditions, with the exception of the corrosion tests in PBS with albumin. Albumin drastically increases the molybdenum concentration in the electrolyte after corrosion tests at applied potentials below the transpassive region of the alloy. In the tribocorrosion tests, an increase of metal ion concentration with potential was found, while this effect was not observed in the corrosion tests, thus electrode potential variations are critical for metal ion release of CoCrMo alloys under tribocorrosion conditions. Combining ICP-MS analysis with electrochemical testing gives mechanistic information on the involved redox reactions, oxide formation and amount of wear debris in corrosion and tribocorrosion situations of biomedical alloys. This is needed for the interpretation of the in vivo data.