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.

In this article an attempt was made to increase the corrosion resistance of Ni– Mo alloy coatings with the addition of small quantity of CdCl₂ into its bath. The limiting of limiting current density (i_L) of Ni in both Ni–Mo and Ni–Cd baths due to inherent induced and normal type of codeposition has been successfully alleviated by addition of 1 g/L of CdCl_2.The advent of induced and normal type of codeposition of individual binary baths has been used to optimize the Ni content of the ternary deposit for better corrosion stability. The composition vs. current density plots of all coatings have been studied, and thereby optimali_L of Ni in all baths were assessed. The content of Mo was found to be decreased with the small addition of Cd to the bath. Results revealed that (Ni–Mo–Cd)_{6.0 Adm}⁻² coating showed better corrosion resistance by reducingi_L of Ni, on addition of Cd⁺² ions into the bath and was explained in the light of diffusion limited deposition of Ni⁺² ions. The results were supported by SEM (scanning electron microscopy), XRD (X-ray diffraction) and AFM (atomic force microscopy) study of Ni–Mo, Ni–Cd and Ni–Mo–Cd coatings at optimal current densities.

The corrosion protection efficacy of Ni–Co alloy coatings was tried to improve by magnetoelectrodeposition (MED) approach. The magnetic field of varying strength (B) was applied in perpendicular and parallel to the direction of diffusion of metal ions, simultaneously to the process of deposition. The corrosion behaviour of the deposited coatings was studied through electrochemical DC method and results revealed that Magneto-electrodeposited (MED) Ni–Co alloys coatings were found to be more corrosion resistant than their conventionally electrodeposited (ED) counterparts. Moreover, the effect of magnetic field is more pronounced in perpendicular field direction and was explained by Lorentz force. Under optimal condition, MED Ni–Co alloy coating obtained at a magnetic field intensity of B = 0.3 T (Perpendicular) was found to be less prone to corrosion than its ED alloy (B = 0 T) counterpart. The increased limiting current density (i_L) of Co²⁺ ions in turn increases the corrosion resistant properties of MED Ni–Co alloy coatings. The effect of magnetic field on improved corrosion resistance of the deposited coatings have been investigated in terms of their changed surface morphology, composition, phase structure and surface roughness using Scanning electron microscopy (SEM), Energy dispersion spectroscopy (EDS), X-Ray diffraction (XRD) technique and Atomic Force Microscopy (AFM) respectively.

This paper reports the production of Ni–Zn multilayer alloy coating to improve the anticorrosive behavior of the mild steel material. The deposition technique follows the square wave current pulse technique. Initially, the effect of current densities on the anticorrosive behavior of the Ni–Zn was investigated. Later, the current densities were optimized in different combinations to get a multilayer of Ni–Zn with different degrees of layering. The Ni–Zn multilayer coatings were developed on the surface of mild steel with different numbers of layers by square pulsing current density of 1 Adm⁻² and 3 Adm⁻². The deposited Ni–Zn alloy coating was studied for its electrochemical behavior toward corrosion. Results revealed that the anticorrosive behavior of the multilayer Ni–Zn alloy coating was found to be many folds higher than that of monolayer Ni–Zn alloy coating. The comparison study of corrosion data revealed that (Ni–Zn)_1/3/300 multilayer coatings are less prone to undergo corrosion among all developed monolayer and multilayer coatings. The corrosion rate of (Ni–Zn)_1/3/300 was found to be less and in the range of 0.37 mm year⁻¹ among all developed coatings.