Influence of current density onto composition and corrosion of electrodeposited Ni–Zn alloys

 The initial corrosion rates of electrodeposited Zn-Ni coating under galvanostatic conditions are closely related to the current density. The NH4Cl 12-14 wt% Ni coating showed better corrosion resistance than those of the other investigated coatings due to the lower Ni content of 9 wt%. Moreover, nodular granules closely packed with capillary fissures, along with the formation of the electrochemically noble γ-Ni5Zn21 phase, were observed at the highest Ni concentration of 10 wt%. The results of electrochemical characterization on the copper substrate showed an extended testing time, indicating a nobler corrosion potential. Additionally, the grain size refines with the presence of NH4Cl, and the increase in cathodic current density can also lead to a decrease in grain size.The experimental results indicate that Zn-Ni alloy coatings obtained in the presence of NH4Cl exhibit favorable electrochemical properties, demonstrating a protective effect on steel substrates. However, the sacrificial effect is more pronounced when these coatings are applied on copper substrates.