Improvement of corrosion resistance of Cu-based bulk metallic glasses by the microalloying of Mo

(Cu47Zr11Ti34Ni8)100−xMox bulk metallic glasses (BMGs) with x = 0, 1 and 2 at% were prepared by water-cooled copper mold casting. The effect of the addition of a small amount of Mo on the corrosion resistance of the Cu-based BMGs was examined by electrochemical polarization and weight loss measurement in 1 mol/L H2SO4 open to air. It is found that the corrosion resistance of Cu-based BMGs enhanced with increasing Mo content, as indicated by the decrease in passive current density and corrosion rate with the increase in Mo content. X-ray photoelectron spectroscopy (XPS) was employed to study the composition and the state of elements in the passive film, which revealed that the improvement of corrosion resistance of Cu-based BMGs microalloyed with Mo originated from the enrichment of ZrO2 and TiO2, but depletion in Cu- or Ni-oxide in the passive films formed during electrochemical polarization. In addition, the galvanostatic-step measurement was performed to investigate the formation kinetics of the passive films. It is demonstrated that the addition of an appropriate amount of Mo can promote the formation of the passive film on the surface.