Theoretical and experimental study of electroplated γ-Ni₂Zn₁₁ coatings from a non-aqueous electrolyte: effect of additives on the coating's microstructure, texture characteristics and mechanical properties

Abstract

The viability of 5,5-dimethylhydantoin (DMH) and ethylenediaminetetraacetic acid (EDTA) as complexing agents in the electrolytic baths is systematically studied using experimental and theoretical approaches. The ZnNi alloy-based coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and nano-indentation studies. Cyclic voltammetry (CV) studies were carried out to study the electrochemical behavior and deposition kinetics of the electrolytic baths with and without the presence of additives. Density functional theory (DFT) calculations indicate that in DMH-based baths, the dissociation energy required to release Ni from the additives is higher than that for Zn, whereas in EDTA baths, Zn dissociates more easily than Ni. The diffusivity of Ni in baths containing EDTA is higher than in baths containing DMH, leading to higher amounts of Ni in the coatings obtained from EDTA baths (~16 wt% Ni). Furthermore, the coatings' texture analysis reveals a change in preferred crystallographic texture from {110}〈001〉 to {001}〈100〉 as the concentration of DMH increases from 0.1 to 0.5 M in the baths, differing from the coatings obtained from EDTA baths at all concentrations which displays {110}〈001〉 components.