Oxygen impurity improving corrosion resistance of a Zr-based bulk metallic glass in 3.5 wt% NaCl solution

The effect of oxygen impurity on corrosion behavior of as-cast Zr₆₁Ti₂Cu₂₅Al₁₂ bulk metallic glasses (BMGs) is clarified using electrochemical measurements, microstructure characterization and surface analyses. We find unexpectedly that oxygen impurity (≤1200 ppm) improves pitting corrosion resistance when a fully amorphous structure is attained. The oxygen-induced annihilation of free volume enhances passive film protectiveness and hence accounts for the improved corrosion property. In contrast, adding more oxygen impurity (1800 ppm) deteriorates pitting corrosion resistance by assisting the formation of highly-reactive crystalline phases. The finding herein provides an avenue for designing new low-cost Zr-based BMGs with superior properties by oxygen microalloying.