Effect of frequency and duty cycle on corrosion and wear resistance of functionally graded Zn–Ni nanocomposite coating

Abstract

ABSTRACTIn this study, functionally graded Zn–Ni nanocomposite coatings with a nanoparticle mix of 80 wt-% alumina, 5 wt-% yttria and 15 wt-% graphene were electrodeposited on a mild steel substrate by the pulsed current method. The effects of pulse parameters such as frequency and duty cycle on chemical composition, microstructure, corrosion resistance and tribological properties of coated specimens were evaluated. The coatings were formed through changing the duty cycle from 10% to 90% in five steps during the coating process and different frequencies of 500, 1000, 3000 and 5000 Hz. A continuous decrease in the duty cycle led to an increase of the nanoparticles embedded in the coating structure from the interface to the surface, so that most increments corresponded to the sample with a 500 Hz frequency and was 1.41 wt-%. By increasing the frequency, Ni and nanoparticle content in the coating surfaces increased up to 3.6 wt-% and 1.82 vol.-%, respectively. In particular, by increasing the frequency and nanoparticle content in the coatings, corrosion and wear resistance of coatings improved.