The electrochemical behaviours of binary and ternary copper-based alloys and individual metal components were investigated in a borate buffer with and without the addition of chloride ions. Compared to the pure Cu metal, all the Cu-based alloys were more susceptible to localized corrosion attack caused by the chloride ions. However, their resistance was significantly better than that of the pure zinc metal. The electrochemical activity of the alloying elements indicates that they contribute to the composition of the passive layer, which changes from Cu/Cu2O/CuO on the pure Cu metal to NiO/Cu2O/CuO and ZnO/Cu2O/CuO on the Cu-20Ni and Cu-20Zn alloys, respectively. The electrochemical behaviour of the ternary Cu-18Ni-20Zn alloy is similar to that of the binary Cu-20Ni alloy. (c) 2007 Elsevier B.V. All rights reserved.