Theory and technology for electroplating a rose golden Cu–Zn–Sn alloy using a disodium ethylenediamine tetraacetate system

Abstract

A non-cyanide rose golden electroplating system was investigated in this work. The electroplated layer of Cu–Zn–Sn alloy was also investigated using a disodium ethylenediamine tetraacetate (EDTA·2Na) system, in which CuSO4·5H2O, ZnSO4·7H2O and Na2SnO3·3H2O were the main salts. EDTA·2Na acted as a complexing agent. Finally, NaOH acted as a buffering agent in the electroplating solution. The effects of different electroplating solutions on colour, micro-topography, composition and phase structure of the electroplated layer was analysed by photo analysis, SEM, EDS and XRD. Meanwhile, different electroplating solutions were analysed and compared by electrochemical analysis and UV–Vis, FTIR and NMR spectroscopy. A rose golden electroplated layer of Cu–Zn–Sn alloy could be obtained by adjusting the amount of the main salts. The composition of the electroplated layer was 98.81% Cu, 0.77% Zn and 0.42% Sn. Moreover, the electroplated layer was composed of regular 50–100 nm particles. The composition of the ternary alloy-electroplated layer was Cu, Cu5Zn8 and Cu10Sn3 phase. At the same time, the cathode only had a single deposition peak at − 1.22 V by electrochemical analysis of the electroplating solution. UV, IR and NMR analyses show that a chelate was formed with EDTA·2Na and metal ions in an alkaline environment. These results may provide a theoretical guidance for a new technology for Cu–Zn–Sn alloy electrodeposition.