XRD, SEM and EIS analysis of electroplated Cu-Zn alloy using Zinc oxide bath

Abstract

Substitution of cyanide in electroplating is a current challenge. We present an alternative method aiming to reduce the toxicity and the cost of electroplating of Cu-Zn alloy (usually prepared from cyanide baths) while maintaining the decorative qualities and anticorrosive properties of the coating. For this purpose, Cu-Zn alloys were obtained in two steps from non-cyanide electrolytes. First, a copper layer electrodeposited onto a nickel under-layer, followed by a thin layer of zinc from three different simple non-cyanide zinc baths. The Zn/ Cu/Ni sandwich system was then subjected to heat treatment at a temperature of 400°C, to ensure the diffusion of zinc into the copper layer to give the desired Cu-Zn alloy structure. The synthesized films were characterized by using X-ray diffraction XRD, scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). XRD demonstrated that the electrodeposited films are crystalline and present the Cu_0.7Zn_0.3 phase with pre- ferential (111) orientation. An analysis of XRD patterns revealed that after heat treatment, the Cu-Zn alloys were composed of a predominating α-phase structure. The morphology and composition of the coatings depends on the zinc plating bath type. After annealing, well defined pseudo-spherical Cu-Zn grains were formed covering the entire substrate surface. The EDS analysis indicated the formation of Cu_0.7Zn_0.3 brass alloys, corrosion was stu- died by impedance spectroscopy. The results showed the feasibility of this low-cost new route for the preparation of good quality Cu–Zn alloys from cyanide-free electrolytes.