Electrodeposition of copper–zinc from an alkaline bath based on EDTA

The electrodeposition of copper–zinc on 1010 steel from a non-cyanide alkaline electrolyte based on EDTA (ethylenediaminetetraacetic acid, disodium salt) — alkaline with various proportions of copper and zinc ions, was investigated. The complexation of copper and zinc by EDTA stabilized the solution. The deposition potential and the composition of the Cu–Zn bath were shown to influence the composition, morphology and phase composition of the Cu–Zn deposits. Scanning electron microscopy analysis showed that the best conditions to obtain smooth Cu–Zn deposits were at − 1.45 V, with Cu70–Zn30 and Cu50–Zn50 baths, and at − 1.60 V, with Cu30–Zn70. Besides being smoother than others, these deposits were golden in colour. Energy-dispersive X-ray spectroscopy analysis showed that a Zn content above 60 wt.% in the Cu–Zn deposits was achieved from the last bath, at − 1.45 V. X-ray diffractograms of the Cu-Zn deposits produced at -1.45 V, from Cu70-Zn30, Cu50-Zn50 and Cu30-Zn70 baths, indicated the occurrence of phases Cu0.61Zn0.39 and Cu, CuZn, Cu5Zn8 and Cu, CuZn, Cu5Zn8, CuO, Cu0.61Zn0.39, respectively. For the Cu30–Zn70 bath at − 1.60 V, Cu, CuZn, Cu5Zn8, and CuO phases were observed.