Insights on the Role of Copper Addition in the Corrosion and Mechanical Properties of Binary Zr-Cu Metallic Glass Coatings

The effect of copper addition on the corrosion resistance and mechanical properties of binary Zr100-xCux (x = 30, 50, 80, 90 at.%) glassy coatings was investigated by means of electrochemical measurements, scanning electron microscopy (SEM), energy dispersive analysis spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and nano-indentation techniques. The corrosion resistance in 0.01 M deaerated H2SO4 solution and the mechanical properties of the Zr-Cu glassy coatings depend considerably upon the copper content in the glassy matrix. The top surfaces of the Zr-Cu coatings with lower Cu content were covered by a compact protective ZrO2 passive film. The competition between the oxidation of Zr atoms (ZrO2 film formation) and the oxidation-dissolution of Cu atoms assumed the most important role in the electrochemical behavior of the Zr-Cu glassy coatings. The generation of ZrO2 on the surface benefited the formation of passive film; and the corrosion resistance of the metallic glass coatings depended on the coverage degree of ZrO2 passive film. The evolution of free volume affected both the mechanical and corrosion behaviors of the Zr-Cu glassy coatings.