The stability of Cu-Al-Ni ternary alloys used in the manufacturing of NaCl and Na2SO4 from Lake Qaroun in Egypt was investigated in sulfate-chloride electrolytes. Different electrochemical techniques were used. The results show that the increase in the nickel content improves the stability of the ternary alloys due to formation of a stable barrier film. The barrier film behaves like an ideal capacitor and its stability is affected by the chloride ion concentration. An equivalent circuit model for the electrode/electrolyte interface was proposed and the experimental impedance data were fitted to theoretical data according to this model. The surface morphology and barrier layer constituents were investigated by SEM/EDAX unit. (C) 2012 Elsevier Ltd. All rights reserved.