Electroplating of Zn-Ni Alloy Coating on Mild Steel and Its Electrochemical Studies

A new sulfate bath having ZnSO₄.6H₂O, NiSO₄.6H₂O, citric acid, and methanol extract in combination was optimized for the deposition of Zn-Ni electroplating on mild steel. The bath composition and operating conditions were optimized by the Hull cell experiment. The effect of current density (CD), pH, and temperature on coating properties like Ni content, hardness, thickness, throwing power, and corrosion resistance was discussed. The corrosion performance has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy methods. The antibacterial activity of the extract was carried out by the agar diffusion method. The electroplating having about 1.51% of nickel content (at optimized current density 4 A dm^-2) was found to be bright and uniform, showing good corrosion performance against corrosion, and shows the highest corrosion resistance (8.62 μA cm^-2) at optimized current density 4 A dm^-2. The microstructures of the deposits were examined with scanning electron microscopy (SEM). The nickel contents in the deposit were analyzed with colorimetric technique and cross-checked by energy-dispersive x-ray analysis (EDX). A novel sulfate bath for Zn–Ni alloy coating on mild steel has been proposed and results are discussed.