Effects of Current Density and Bath Temperature on the Morphological and Anticorrosive Properties of Zn-Ni Alloys

The effect of current density and bath temperature in the electroplating process on resistance to corrosion of Zn-Ni alloys was evaluated in this work. The electrolytic bath consisted of nickel sulfate, zinc sulfate, sodium sulfate, boric acid, and sodium citrate at pH 7.0. The current density was varied in the range 20-80 mA/cm2 and the bath temperature in the range 30-60 degrees C. Increasing, independently, the current density or the bath temperature increased the nickel content in the obtained alloy, which affected the alloy microstructure, with a predominant gamma phase and cauliflower-like morphology. The nickel content in the alloys was in the range 20-42%wt. A synergistic effect between the current density and bath temperature was observed from a design of experiments and response surface models. The maximum resistance to corrosion occurred for the alloy containing 42%wt. nickel. This alloy was obtained at upper levels of current density and bath temperature, presenting a corrosion potential of -0.789 V and polarization resistance of 4136 omega.cm2.

Automated summary

This work evaluated the effect of current density and bath temperature on the corrosion resistance of Zn-Ni alloys in the electroplating process. The results showed that increasing the current density or bath temperature independently increased the nickel content in the obtained alloy, affecting the microstructure. A synergistic effect between the two factors was observed, and the alloy with 42%wt. nickel had the highest corrosion resistance.