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Corrosion behaviour of sputter-deposited Mg–Zr alloys was examined in a borate buffer solution of pH 8.7. XRD measurements showed that the alloys were supersaturated with Zr. The addition of 29 at.% Zr or more was very effective in increasing the corrosion resistance of Mg by more than four orders of magnitude. XPS analysis of spontaneously formed passive films revealed that the passive film consisted of double oxyhydroxide composed of enriched tetravalent Zr and divalent Mg cations. The enrichment of Zr cations in the passive film is responsible for the enhanced corrosion resistance of Mg–Zr alloys.

The electrochemical behavior of Cu–Ni alloys in acidic chloride medium was investigated. Commercial Cu–Ni alloys were investigated using potentiodynamic techniques, complemented by electrochemical impedance spectroscopy. The influence of alloy composition, chloride ion concentration and immersion time on the electrochemical response of the alloys was analyzed. Results of present investigations with pure metals (Cu and Ni) are also considered in this paper for the sake of comparison. Potentiodynamic measurements reveal that the increase in nickel content decreases the corrosion rate of the alloy and when the nickel content exceeds 30%, an increase in the corrosion rate was recorded. Also, the corrosion current density increases with increasing the concentration of chloride ions up to 0.6 M. The experimental impedance data were fitted to an equivalent circuit model representing the electrode/electrolyte interface. The relevance of the proposed model to the corrosion/passivation phenomena occurring at the electrode/solution interface was discussed.