The effects of duty cycles on pulsed current electrodeposition of Zn[sbnd]Ni[sbnd]Al2O3 composite on steel substrate: Microstructures, hardness and corrosion resistance

Abstract

In this study, we examine the effect of duty cycles (33%, 50% and 67%) under square-wave galvanostatic pulses on the electrodeposition of zinc-nickel-alumina (ZnNiAl2O3) composites from a sulfate bath. XRD results showed that the dominant phases of the ZnNiAl2O3 electrodeposits were mixtures of Zn21Ni5 and Zn22Ni3 phases together with as Al2O3. The Ni content measured in the electrodeposits using EDS varied from 9.73 to 13.47 wt%. SEM results showed that finer and smoother surface electrodeposits were obtained by pulsed current electrodeposition at a low (33%) duty cycle. In addition, the corrosion properties of the electrodeposits were characterized by Tafel plots and electrochemical impedance spectroscopy (EIS), while the microhardness of the electrodeposits was measured by a Vickers hardness tester. In summary, this study revealed that pulsed current electrodeposition at a 33% duty cycle led to a finer and smoother surface morphology, an enhanced strength, a greater corrosion resistance, and a higher Ni content in the ZnNiAl2O3 composite coatings compared to plating at higher duty cycles or plating through DC electrodeposition.