The development of cost-effective coatings with exceptional corrosion resistance is an ongoing challenge in the field of materials science. Among the promising coatings, zinc–nickel (Zn–Ni) coatings have shown great potential, especially when produced using economical electroplating technology. However, achieving optimal performance while minimizing coating thickness remains a complex task. In this study, the behavior of the responses was investigated according to the coating standards and levels, focusing on eight variables including temperature, time, cathodic current density, nickel concentration, substrate hardness, roughness, cathode–anode distance, and magnetic stirring speed. Four responses were investigated: coating thickness, roughness, microhardness, and corrosion rate with potentiodynamic polarization, using two design of experiments (DOE) methods: Plackett–Burman design (12 runs) and response surface methodology with Box–Behnken design (15 runs). The results show the degree of influence of each variable on the responses and their contribution to changing the responses. Additionally, response surfaces have been determined and it is shown that large response values can be achieved with small thicknesses. The morphological study using SEM, EDX, and XRD techniques revealed that the deposition conditions play an important role in the surface morphology. Some samples showed microcracks, while others had small grain size and were free of cracks and pores. Overall, this study provides new insights into the improvement of Zn–Ni coatings with exceptional corrosion resistance and cost-effectiveness.

The protective Zn-alloy coating enhances the carbon steels' corrosion resistance. Seven factors of Zn-Ni coating electroplating on medium carbon steel were optimized using Taguchi L27 (37) orthogonal array. The impact of nickel chloride concentration (N), distance factor between anode and cathode (X), plating process time (P), bath temperature (T), deposition current density (I), substrate hardness (H), and substrate roughness (R) on the corrosion current density (ICorr) and the coating thickness were examined. Two different samples were also morphologically studied. Results indicated that N:20 g l-1; X:9 cm; P:20 min; T:45 °C; I:3 A dm-2; H:44 HRC; and R:P500 can produce Zn-Ni coating with the highest corrosion resistance (lowest ICorr) with inhibition efficiency of 96.5%. Among factors, T, P, H, and N had the highest impact on ICorr with a total percentage contribution of about 60%. In addition, the thickness was mainly affected by I, P, and H, with a total percentage contribution >90%. The optimal combination for lowest ICorr resulted in a smooth and more homogenous and compact structure of coating without microcracks. Higher microhardness was also obtained due to the high nickel content in Zn-Ni coating (14.7%wt). However, the worst combination gave semi-spherical-shaped crystallites with non-uniform distribution of particles.