Electrochemical studies of laser-treated Co-Cr-Mo alloy in a simulated physiological solution

The aims of this work were to study the crevice corrosion resistance of laser-treated Co-Cr-Mo alloy by electrochemical techniques and to characterize the electronic properties of the passivating films. Open-circuit experiments and cyclic polarizations with crevice-free samples have been carried out as well as electrochemical impedance spectra using Bode-Nyquist and Mott-Schottky techniques. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis have been used in order to evaluate surface modifications. It has been observed that laser-treated Co-Cr-Mo alloy shows good corrosion resistance in spite of some degradation at the dendrites formed during treatment. By XPS it was found that at 6–9 nm depth there exists an enrichment in oxygen and a decrease of Cr which could have a slight effect on the corrosion resistance and it was seen that the film is mostly formed by Cr₂O₃. Mott-Schottky plots show that a possible transition from n-type to p-type semiconductivity may have occurred.