Microstructure And Properties Of Electroplating Aluminum Coating Treated By Micro-arc Oxidation Process On Q235 Steel

The phase used electroplating aluminum in molten salt, and the electroplating aluminum on Q235 steel obtained by electroplating in molten salt of AlCl₃-NaCl-KCl was treated by micro-arc oxidation in Na₂Si₂O₃ solution system for different time. The morphologies and phase structure of electroplating aluminum coating treated by micro-arc oxidation were investigated by means of SEM and XRD, and the hardness,wear resistance and corrosion resistance of the treated aluminum coating was also examined.The results show that after the electroplating aluminum coating was treated by the micro-arc oxidation for different time, the morphology of surface of the coating was similar as those of surfaces of aluminum and its alloys treated by micro-arc oxidation, the shape of electroplating aluminum coating treated was of porous melting solidification, and the hole's sizes on the surface increased with the micro-arc oxidation prolonging. The coating treated 30min was composed ofγ-Al₂O₃ and Al, and the thickness of oxidation film increased with the micro-arc oxidation prolonging. The hardness of the electroplating aluminum coating was improved remarkably after micro-arc oxidation treatment, with micro-arc oxidation time increasing, the hardness of oxidation film increased. The hardness of the electroplating aluminum coating was 571 HV0.01 after 30min micro-arc oxidation treatment, and was enhanced 7 times compared with the original electroplating aluminum coating. The friction coefficient of the electroplating aluminum coating which was treated by micro-arc oxidation for different time decreased first and then increased with the increase of time, and the friction coefficient was up to the minimum value after 20min micro-arc oxidation treatment. The wear resistance of electroplating aluminum coating had a considerable drop after micro-arc oxidation treatment, and with micro-arc oxidation time increasing, the wear volume decreased. After 30min micro-arc oxidation treatment, the wear volume decreased to 1/400 compared with the that of original electroplating aluminum coating. In 3.5% NaCl solution the corrosion resistance of electroplating aluminum coating was improved much after micro-arc oxidation treatment, and the corrosion resistance increased first and then decreased with increase of time, and the corrosion resistance of the electroplating aluminum treated by micro-arc oxidation for 20 min was the best.