Growth behavior and corrosion resistance of micro-arc oxidation film on SiC_p/Al matrix composites

The micro-arc oxidation film was fabricated on SiC_p/Al matrix composites in an aluminate electrolyte. The growth behavior of micro-arc oxidation film on the surface of SiC_p/Al matrix composites was studied by analyzing the changes of current density and temperature, film morphology, interfacial structure and phase. The corrosion resistance of the film was analyzed by potentiodynamic polarization curve and electrochemical impedance spectroscopy. The results show that the film is preferentially formed in the Al substrate and the interface between SiC particles and Al of SiC_p/Al matrix composites at the initial stage of micro-arc oxidation. The stable growth of the film is realized through the continuous breakdown and discharge of the weak part and the repeated aggregation. The growth mode is inward and outward growth, and mainly outward growth. The interface between the substrate and the film of SiC_p/Al matrix composite consists of three kinds of structures, which are the amorphous oxide structure formed by Al and O near the Al substrate at the interface, the dense amorphous oxide structure formed by Si and O near the SiC particles, and there are many micro and nanoporous structure. The corrosion resistance of SiC_p/Al matrix composite can be improved effectively by micro-arc oxidation film. After soaking for 168 h, the corrosion potential of the film is −1.212 V, the corrosion current density is 2.767×10⁻⁵ A·cm⁻², and the corrosion resistance of the film is still better than that of the substrate.