Influence of structural factor on corrosion rate of functional Zn–Ni coatings

This study investigates the electrocrystallization processes of zinc-nickel (Zn–Ni) coatings from weakly acidic sulfate solutions enriched with citrate and acetate complexing agents. The primary objective was to compare the deposition kinetics and analyze the impact of different electrolyte compositions on the physicochemical properties of the coatings, particularly focusing on corrosion resistance, texture, phase composition, and morphology. The methodology included systematic experimentation under controlled conditions to assess the influence of nickel and zinc concentration ratios along with alterations in pH levels. The findings revealed significant variations in the properties of the coatings produced from acetate and citrate solutions, with the former yielding deposits richer in nickel. Notably, the corrosion resistance was found to correlate closely with nickel content; however, coatings with lower nickel concentrations from sulfate-citrate solutions displayed comparable corrosion resistance to their nickel-rich counterparts. This was attributed primarily to differences in phase composition, as citrate-derived coatings predominantly exhibited a single-phase hexagonal structure, offering superior protective qualities at lower corrosion rates compared to multi-phase coatings from acetate baths. The study underscores the crucial role of complexing agents in tailoring the corrosion resistance of Zn–Ni alloys.