Effects of pulse plating parameters on the microstructure and properties of high frequency pulse electrodeposited Ni–Co/ZrO2 nanocomposite coatings

Abstract

Ni–Co/ZrO2 nanocomposite coatings were fabricated in a modified Watt’s bath by using high frequency pulse electrodeposition and the effects of pulse parameters such as frequency and duty cycle on the microstructure and properties were investigated. The surface morphology, phase structure, and microhardness of the Ni–Co/ZrO2 nanocomposite coatings were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction and Vickers’ microhardness tester. The corrosion behaviour of the nanocomposites was evaluated by electrochemical impedance spectroscopy in the 3.5 wt% NaCl solution. The results revealed that increasing frequency and duty cycle resulted in a change of morphology from rough and porous structure to compact and homogeneous structure and reduced the ratio of relative intensity I(200)/I(111) of the Ni–Co/ZrO2 nanocomposites by intervening the adsorption–desorption of interfacial inhibitors at the cathode/solution interface. Furthermore, the effects of frequency and duty cycle on the microhardness of Ni–Co/ZrO2 nanocomposites should be associated with the ZrO2 nanoparticles according to dispersion strengthening from Orowan mechanism. It has been found that the corrosion resistance of the nanocomposites in 3.5 wt% NaCl solution depended on the incorporation of ZrO2 nanoparticles and the phase structure of Ni–Co/ZrO2 nanocomposites.