The rules of growth of the micro-arc oxidation coating on aluminum alloy

In order to improve the effectiveness of the MAO (micro-arc oxidation) coating on aluminum alloy (LV12), several comparative studies were made on ceramic coatings growth, which were associated with analyzing of the microstructure and morphology of MAO coating under different working time and working current densities, positive pulse and bipolar pulse modes, different pulse frequencies, respectively, using a homemade pulse power supply in the KOH-Na2SiO3 solution. The thickness of the coating was measured using the eddy current thickness indicator; the hardness was measured using HVS-1000 micro hardness Vickers tester. Scanning electron microscopy (SEM) was employed to characterize the microstructure and morphology of the coating and to study the rules of growth of the MAO coating on Aluminum alloy. The results show that the coating grows with higher thickness and hardness when the processing time and current density are increased. The bipolar pulse mode power supply can process the MAO coating with better properties. It is also found that the higher pulse frequency is one of the key factors to advance the properties of the MAO coating.