Interactive effects of albumin and phosphate ions on the corrosion of CoCrMo implant alloy

The corrosion behavior of CoCrMo alloy in simulated body fluids has been analyzed by electrochemical techniques and surface analysis. Interaction of albumin and phosphates present in the body fluids on the passive film of the alloy was also investigated. Electrochemical techniques such as potentiodynamic and potentiostatic polarization and electrochemical impedance spectroscopy were employed. Further, ex situ X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis of the passive films were carried out. The study reveals that phosphates and proteins present in simulated body fluid play a significant role in the electrochemical properties of the metal/oxide/electrolyte interface. Surface analysis showed that both species competitively adsorb on the alloy surface. For a given passive potential, the impedance behavior of passive CoCrMo was found to depend on the way passive conditions were established. A simple model has been developed assuming a multilayer structure of the surface including an outer layer where albumin and phosphate ions adsorb, the passive film (inner layer), and the metal. This model is consistent with the obtained electrochemical and surface analysis results. (c) 2007 The Electrochemical Society.