The effect of co-electrodeposited ZrO₂ particles on the microstructure and corrosion resistance of Ni coatings

Abstract

Pure Ni and Ni–ZrO₂ composite coatings were electroplated using a Watt’s bath containing different amounts of ZrO₂ to be co-deposited. Surface morphology and microstructure of the samples and particle distribution in the coatings were studied using optical microscope, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The results showed that the electroplated sample in the bath containing 90 g l⁻¹ ZrO₂ has the maximum particle content and the best particle distribution. Evaluation of microstructure and corrosion behavior demonstrated that with increasing ZrO₂ content in the coating, the corrosion potential shifted toward noble and positive values. This is probably due to diminishing of the metallic surface area exposed to the solution. Higher ZrO₂ contents in the coating results in lower corrosion current densities probably due to the changing of the microstructure from coarse-grained columnar to fine-grained granular structure. The results revealed that the electroplated sample in the bath containing 90 g l⁻¹ ZrO₂ has the best corrosion resistance.