Preparation and characterization of the electrodeposited Cr–Al2O3/SiC composite coating

To increase the SiC content in Cr-based coatings, Cr–Al2O3/SiC composite coatings were plated in Cr(VI) baths which contained Al2O3-coated SiC powders. The Al2O3-coated SiC composite particles were synthesized by calcining the precursor prepared by heterogeneous deposition method. The transmission electron microscopy analysis of the particles showed that the nano-SiC particle was packaged by alumina. The zeta potential of the particles collected from the bath was up to +23 mV, a favorable condition for the co-deposition of the particles and chromium. Pulse current was used during the electrodeposition. Scanning Electron Microscopy (SEM) indicated that the coating was compact and combined well with the substrate. Energy dispersive X-ray analysis of Cr–Al2O3/SiC coatings demonstrated that the concentration of SiC in the coating reached about 2.5 wt.%. The corrosion behavior of the composite coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The data obtained suggested that the Al2O3/SiC particles significantly enhanced the corrosion resistance of the composite coating in 0.05 M HCl solution.