Influence of electrolyte pH on composition, corrosion properties and surface morphology of electrodeposited Cu–Ni alloy

Abstract

Cu–Ni alloys were electrodeposited by the brush plating technique from sulphate/citrate electrolyte at various pH values. The effects of pH on composition and surface morphological properties of alloys were investigated by X-ray fluorescence and atomic force microscopy. The Cu content increased in the composition of Cu–Ni alloy at electrolyte pH 2. The deposition mechanisms of Cu, Ni and Cu–Ni were investigated by cyclic voltammetry. The lower electrolyte pH leads to the higher reduction current density. The corrosion behaviours of the deposits at different pH values were investigated by Tafel analysis and electrochemical impedance spectroscopy. The corrosion studies indicate that the Cu–Ni alloy exhibits better corrosion resistance at higher pH values than at lower pH values. The surface roughness decreases with increasing solution pH and this observation was confirmed by atomic force microscopy measurements.