Fabrication and performance of composite coating doped with CeO2 nanoparticles by plasma electrolytic oxidation on Cu–Zn alloy surface.

A CeO2-doped plasma electrolytic oxidation (PEO) composite coating was prepared on the surface of Cu–Zn alloys by adding CeO2 nanoparticles into the mixed electrolytes of Na2SiO3·9H2O and sodium hydroxide. Surface microstructure and element composition of PEO coatings were studied by a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Microstructure analysis showed that CeO2 nanoparticles were uniformly deposited on the sample surface, and most of the particles were embedded into PEO coatings. Ce element found in the EDS and XRD analysis confirmed the successful incorporation of CeO2 nanoparticles. Furthermore, with the addition of CeO2 nanoparticles, the coating porosity decreased gradually, while the thickness and surface roughness of PEO coatings decreased and then increased. Corrosion resistance of PEO coatings was investigated by using a potentiodynamic polarization test. The results show that the addition of CeO2 nanoparticles has significantly improved the corrosion resistance of PEO coatings. Especially, the corrosion current density of the PEO coating with 4 g/L CeO2 concentration is 3 orders of magnitude more than that of the bare alloy substrate. [ABSTRACT FROM AUTHOR]