Influence of graphene particles on the micro-arc oxidation behaviors of 6063 aluminum alloy and the coating properties

Ceramic coatings with different concentrations of graphene particles were prepared on 6063 Al alloy by Micro-arc oxidation (MAO) technique. Effect of graphene particles on the micro-arc oxidation behaviors and coating properties was investigated. The results showed that: The addition of graphene particles reduced the breakdown voltage and promoted the reaction of MAO. The MAO coating thickness and hardness increased with graphene particles. XRD patterns confirmed that all the MAO coatings mainly contained γ-Al2O3 phase, and characteristic peaks of graphene were detected by Raman spectra. The SEM observation indicated that the coating porosity was reduced with discharge holes plugged up when the content of graphene particles was more than 0.15 g/L, and cracks appeared as the concentration was 0.2 g/L. Electrochemical corrosion tests (polarization curve and EIS) showed that the corrosion resistance of the composite coatings with graphene particles increased greatly, and the best corrosion resistance was found in the coating deposited with 0.15 g/L graphene particles. The same results of corrosion resistance were also verified by salt-spray corrosion test.