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Influence of Alloying Elements on the Corrosion of Cobalt Alloys

The behavior of a CoCrMo alloy and its components was studied under in simulated physiological solution (Hank’s solution) using cyclic voltammetry and electrochemical impedance spectroscopy. Cyclic voltammetry allowed us to determine the characteristic potential regions of electrochemical behavior of investigated metals and CoCrMo alloy. The passivation of all samples occurred without an activation-passivation transition, i.e. it took place 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 impedance spectroscopy. The polarization resistance (Rp) and the electrode capacitance (Cdl) were determined. The higher Rp 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 the inductively coupled plasma-mass spectrometry, was in accordance with the values of both the Rp determined from impedance spectroscopy data and current densities measured with cyclic voltammetry.

CoCrMo orthopaedic alloy, Cobalt, Chromium, Molybdenum, Simulated physiological solution

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