Electrodeposition of thin film Cu-Zn shape memory alloys

Cu-Zn alloys have been electrodeposited from a pyrophosphate electrolyte containing Cu₂P₂O₇, Zn₂P₂O₇ salts and an excess of K₄P₂O₇ and KNO₃. Current-potential data for both copper and zinc, as well their plating current efficiencies were determined from electrochemical polarisation experiments. Copper deposition commenced at potentials below -0.208 V whereas zinc was deposited only below -1.157 V. The current efficiencies for both metals were found to be low; typically 20-50% for copper and 5-10% for zinc. Although the potentials for electroreduction for the two components are disparate, alloys of brass containing 30-50%Cu were successfully produced with a current efficiency of 20%. Brass foils as thin as 10μm were produced by this method. The deposits were found to consist predominantly of α and β phases. It was found brass deposition on a copper substrate was preceded by a 1.5 μm thick CuZn₅ layer.