Effect of yttrium addition on corrosion resistance of Zr-based bulk metallic glasses in NaCl solution

This study investigated the effect of yttrium addition on the electrochemical properties of (Zr₅₈Nb₃Cu₁₆Ni₁₃Al₁₀)_100-xY_x (x = 0, 0.5, 2.5 at.%) bulk metallic glasses in 3.5 wt.% NaCl solution. Electrochemical measurements, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were employed. Zr-based bulk metallic glasses exhibited good corrosion resistance. It was ascribed to the formation of a protective passive film which was composed of ZrO₂, Al₂O₃ and a few oxides of other alloying elements, i.e. Y₂O₃. However, the breakdown potential decreased due to the addition of yttrium. Electrochemical impedance spectroscopy (EIS) suggested that yttrium addition could decrease the charge transfer resistance. That is, the addition of yttrium was harmful to the corrosion resistance of this Zr-based bulk metallic glass in 3.5 wt.% NaCl solution. It was attributed to the precipitation of Cu-Y richly quasi-crystal phase owing to yttrium addition, which caused inhomogeneous distribution of copper and yttrium in microstructure.