Microarc oxidation process with spraying cathode applied to LY12 alloy

The spraying microarc oxidation process with a small scale pulsating source was used as field repairing purpose to prepare ceramic coatings in the local damaged region on large size aluminium component instead of the immersing microarc oxidation method. Microstructure and phase composition of coatings were characterized by SEM, XRD and EDS. The corrosion resistance properties of coatings were determined by potentiodynamic polarization and salt spraying test. The results show that under the same applied electrical parameters, the current density during spraying microarc oxidation is slightly higher than that of immersing oxidation, while the coating thickness is lower compared with immersing oxidation. The coating growth shows a similar variation in both oxidation modes. The coating, mainly composed of α-Al₂O₃ and γ-Al₂O₃, is dense in the inner layer, porous in the outer layer. The potentiodynamic polarization and salt spraying test indicates the microarc oxidation coating obviously improves the corrosion properties of LY12 alloy.