Effect of different electrodeposition methods on oxidation resistance of Ni-CeO2 nanocomposite coating

Pure Ni and Ni-CeO2 nanocomposite coatings were prepared by direct current electrodeposition (DC) and pulse current electrodeposition (PC) and pulse current electrodeposition with ultrasound (PC+ultrasound), respectively. The oxidation resistance at 800 °C of three Ni-CeO2 nanocomposite coatings were comparatively investigated. The microstructure of the three nanocomposite coatings before and after oxidation was characterized using scanning electron microscopy (SEM) with EDAX, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the electrodeposition methods can significantly affect the microstructure and the oxidation resistance of Ni-CeO2 nanocomposite coatings and those of the pure Ni coatings. For the same electrodeposition methods, the oxidation resistance of the Ni-CeO2 nanocomposite coatings is clearly superior to the pure Ni coatings. The PC+ultrasound nanocomposite coating has finer grains and exhibits a superior oxidation resistance compared to the DC nanocomposite coating and also the PC nanocomposite coating. The dispersed CeO2 nanoparticles in the coating and the ultrasound agitation during electrodeposition synthetically contribute to the grain refinement of the nanocomposite coatings. Meanwhile, ultrasound agitation further promotes the grain refinement effect of the co-deposited CeO2 nanoparticles. Significant improvement in oxidation resistance of Ni-CeO2 nanocomposite coatings can be attributed to the homogeneously dispersed CeO2 nanoparticles and the finer-grained structure.