Development of Ni-Co alloy coating on mild steel for improved corrosion resistance using the Taguchi method approach

Abstract The Ni-Co alloy system is an attractive material for study because of its excellent corrosion resistance and mechanical performance in industrial applications. In this work, six different Ni-Co alloy coatings were developed on mild steel substrates using the Taguchi method to optimize the electrodeposition parameters. The coating performance was systematically evaluated through hardness, scratch resistance, Tafel extrapolation, and electrochemical impedance spectroscopy techniques. Among the various bath compositions, bath 4 demonstrated superior thermal conductivity and low viscosity, enabling an efficient and uniform deposition process. The Ni-Co coating from bath 4, comprising 87.62 wt% Ni and 12.38 wt% Co, exhibited the highest corrosion resistance, primarily due to its larger crystallite size and reduced grain boundary density. This coating also displayed enhanced scratch resistance and lower surface roughness compared to other samples. In contrast, the coating obtained from bath 7 exhibited the highest hardness value of 574 HV. The Tafel extrapolation results revealed that the Ni-Co coating produced from bath 4 exhibited a corrosion rate nearly five times lower than that of bare mild steel. These findings highlight that optimization of bath composition and process parameters through the Taguchi approach significantly enhances the corrosion and mechanical performance of sustainable Ni-Co alloy coatings on mild steel substrates.