The behavior of a CoCrMo alloy and its components was studied in simulated physiological solution (Hank's solution) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The passivation of all samples occurred spontaneously at the open circuit potential. The composition of the oxide films as a function of the solution components and the applied potential is discussed. The electrochemical properties of the spontaneously passivated electrodes at the open circuit potential were studied by EIS. The polarization resistance (R(p)) and the electrode capacitance (C(dl)) were determined. The higher R(p) of the alloy than of the chromium pointed to the stabilizing effect of the other alloy components. The concentration of the metallic ions in a simulated physiological solution, measured by inductively coupled plasma-mass spectrometry, was in accordance with the values of both the R(p) determined from EIS data and current densities measured with CV.