Mechanically assisted electrochemical degradation of alumina-tic composites

Metal alloys such as Ti-6Al-4V and CoCrMo, known for their biocompatibility and mechanical strength, are common biomaterials for total hip replacements (THR) [1]. The surface of these metallic biomaterials often forms a passive oxide film providing resistance against corrosion or electrochemical degradation. Electrochemical degradation is a charge-transfer process in which metallic materials react and/or interact with the aqueous environment. Such a process always includes oxidation of metallic components and the concomitant reduction of active species in the aqueous environment somewhere else on the implant surface. Whether an electrochemical reaction will occur or not under certain given conditions is governed by its thermodynamic favorability (Gibbs free energy of reaction, ΔG) which is a function of the type and state of reactants, surface property, reaction kinetics, chemical species and their concentration, and temperature, among others [2].