The influence of different concentrations of phosphate ions on the corrosive behavior of a CoCrMo alloy is investigated. The study is conducted using electrochemical techniques (polarization and potentiodynamic measurements, electrochemical impedance spectroscopy (EIS)) and X-ray photoelectron spectroscopy (XPS). It was found that phosphate ions are vastly responsible for the blocking of the active surface with the addition of calf serum having little effect. This is in contrast to titanium where the competition between the adsorption mechanisms of proteins and those relating to phosphate ions was evidenced recently. The formation and quantification of CrO42- as a result of a dissolution of Cr2O3 oxide layer was evidenced using UV/vis absorption spectroscopy. (c) 2008 Elsevier Ltd. All rights reserved.