The effect of serum proteins on the electrochemical behavior of CoNiCrMo

Numerous studies have examined the effect of serum and blood proteins on the general corrosion of metallic biomedical materials. However, it is unclear whether proteins have any effect in the case of CoCr alloys, particularly at physiological concentrations. In this work, potentiodynamic polarization and electrochemical impedance spectroscopy were used to investigate the electrochemical behavior of Co-35Ni-20Cr-10Mo in PBS, PBS with albumin at a concentration (36 g/L) representative of serum, and bovine serum. The corrosion current density (i_corr ) for the CoNiCrMo was changed little by the addition of serum-level albumin to PBS but it was more than halved in serum. Albumin and serum had little effect on the oxide thickness obtained using impedance spectroscopy, but they increased the effective resistance of the oxide consistent with the changes in i_corr . The potentiodynamic and impedance results indicate that the general corrosion behavior of the CoNiCrMo in serum is affected more by other proteins such as globulin rather than by albumin alone. Furthermore, the proteins in serum are beneficial with regard to the general corrosion behavior of the alloy, suggesting that the proteins act predominantly as inhibitors rather than as corrosion promoters that limit phosphate adsorption and associated inhibition.