Electrodeposition of Zn-Ni-ZrO2, Zn-Ni-Al2O3 and Zn-Ni-SiC nanocomposite coatings from an alkaline bath

Zn-Ni-ZrO2, Zn-Ni-Al2O3 and Zn-Ni-SiC nanocomposite coatings were obtained on mild steel substrate by electrodeposition technique from an alkaline bath. ZrO2, Al2O3 and SiC nanoparticles were added to the bath with concentrations of 5 and 10 g dm-3. The effect of current density and particles concentration on the deposit composition, morphology, structure and microharness was studied. The results show that the addition of nanoparticles to the plating solution does not affect significantly Zn-Ni electrodeposition process and alloy Ni percentage. X-ray diffraction patterns of the coatings show only the presence of cubic γ-phase Ni5Zn21. With ZrO2 or Al2O3 nanoparticles, homogeneous and compact deposits with low grain size were obtained. On the contrary, SiC nanoparticles incorporation perturbs the growth of the alloy matrix by reducing γ-phase orientation. ZrO2 and Al2O3 lead to an increase in the coating microhardness, whereas SiC leads to a decrease, due to the strong modification induced in the alloy structure.