THE MICROSTRUCTURES of five Zn-Ni alloy electrodeposits on aluminium-alloy substrates I were studied. The deposits were prepared by controlling the nickel-ion concentration in the chloride bath. The results show that the nickel contents of these deposits increase directly with nickel-ion concentration. The weight-loss data from dry wear testing show a reciprocal correlation with hardness, except for the deposit of lowest nickel content. Furthermore, the corrosion resistance will be improved as the deposits contain higher nickel content. They have a better corrosion resistance while immersed in neutral 3% NaCl solution than they do in acid and alkaline solution. An extra pretreatment is necessary to have a good adhesion in depositing on aluminium-alloy substrates containing Mg.