Influence of Bovine Serum Albumin (BSA) on the Tribocorrosion Behaviour of a Low Carbon CoCrMo Alloy in Simulated Body Fluids

Tribocorrosion, as the interaction between mechanical wear and electrochemical corrosion, has been found to be the main problem causing the failure and limiting the lifetime of metal-on-metal artificial hip joints. Better understanding of the tribocorrosion mechanisms of CoCrMo alloys is needed in order to reduce the degradation of this alloy, especially in the presence of proteins as one of the organic components present in synovial fluid. In this study, tribocorrosion tests of a low carbon CoCrMo alloy in phosphate buffer solution (PBS) with and without bovine serum albumin (BSA) in two different concentrations at different applied potentials (passive and cathodic) were carried out. The results show that the effect of proteins on wear and friction was concentration and potential dependent. In the cathodic domain (absence of very thin passive film), wear was very low in all solutions and the friction was significantly reduced by the addition of BSA to PBS even at low BSA concentrations. However, in the passive domain, the friction and wear were found not to be affected when the BSA concentration was 0.5 g/L, while they were reduced when increasing the BSA concentration to 36 g/L. The tribocorrosion results were rationalized through an existing tribocorrosion model and the effect of BSA on wear and friction was explained by the consideration of physical factors such as changes in viscosity and double layer structure, because in the present results no tribofilm formation was observed.