Surface characterization of the Zn–Ni–Al2O3 nanocomposite coating fabricated under ultrasound condition

Zn–Ni–Al2O3 nanocomposite coating, which was fabricated by eletrodeposition technique with the aid of ultrasound, was investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). The results reveal that 7.2 wt.% nano-alumina particles uniformly dispersed in the matrix of the composite coating. The XPS analyses demonstrate that the outermost layer of Zn–Ni–Al2O3 coating was composed of nano-alumina and Zn(OH)2, while the transition layer between the outermost layer and the Zn–Ni matrix consisted of nano-alumina, metallic Zn, ZnO and metallic Ni. In order to investigate the influences of ultrasonic agitation and the incorporation of nano-alumina on the composition and surface structure of Zn–Ni matrix, the comparison studies of Zn–Ni–Al2O3 nanocomposite coating with Zn–Ni coatings fabricated with and without ultrasound were conducted. The results indicate that ultrasonic agitation resulted in a decrease of Ni content in the Zn–Ni matrix and an increase of the thickness of surface oxide layer; while the incorporation of nano-α-Al2O3 increased the Ni content in the Zn–Ni matrix.