Electrodeposition of Cu-Zn-Sn coating in citrate medium

The electrodeposition of Cu-Zn-Sn (CZT) coating at ambient temperature was investigated. The bath consists of metal salts SnSO4, ZnSO4,7H2O and CuSO4,5H2O and sodium citrate (NaC6H5Na3O7,2H2O) as a complexing agent. For precipitation, the pH is maintained at 5. The reducing of copper, tin and zinc through Cu2HCit3−, Sncit2− and ZnHcit− complexes respectively are confirmed by the presence of three cathodic peaks on the voltammograms realized on steel and ITO glass substrate. X-ray diffraction patterns revealed peaks corresponding to the phases: Cu-Zn cubic, Cu-Sn hexagonal and β-Sn tetragonal. The deposition rate is 35 μm/h. SEM observation and EDAX analysis showed that the coating consists of a uniform CZT layer of which composition is 55% copper, 20% zinc and 25% tin at -1.5V. A preliminary study showed a remarkable improvement in the corrosion resistance of CZT coated steel in comparison with bare steel.