Intensive pitting corrosion of amorphous (a-) Zr 55 Cu 45 and a-Zr 50 Cu 50 were observed by immersion in 0.2-200 mM NaCl solutions open to air at room temperature. The decreased corrosion rate in Ar-purged NaCl solution and no corrosion in ultrapure water open to air suggested that dissolved O 2 and Cl À played an important role on the corrosion of the ZrCu-base amorphous alloys. The open-circuit potential showed a negative shift with increasing the NaCl concentration from 0.2 to 200 mM like that of pure Cu. These observations suggest that the corrosion of the ZrCu-base amorphous alloys in the NaCl solutions was triggered by Cu dissolution which was induced by the reduction of dissolved O 2 . The dissolution of Cu and Zr self-catalytically progressed by the local concentration of Cl À and hence the corrosion pits and holes were intensively formed even at the thinner NaCl concentrations.