Influence of NH₄VO₃ Addition on Color and Corrosion Resistance of Micro-arc Oxidation Ceramic Film on Aluminum Alloy

Using micro-arc oxidation（MAO） technology, the black ceramic film was prepared on the surface of 2A12aluminum alloy by adding NH₄VO₃ to the silicate system electrolyte. The microscopic morphology and element composition of the ceramic film were analyzed by SEM and EDS. The thickness of the film was measured with the coating thickness gauge.The Tafel polarization curve and electrochemical impedance spectroscopy（EIS） were used to study the electrochemical corrosion behavior of film in the mass fraction of 3.5% NaCl solution.The results show that with the increase of NH₄VO₃ mass concentration, the blackness and thickness of the ceramic coating increase, while the corrosion resistance of the coating decreases and the surface roughness increases. The mass concentration of NH₄VO₃ should not be too high, otherwise the black ceramic film is easily mixed with a few fine gray-white markings. When the mass concentration of NH₄VO₃ is 7.5 g/L, the black purity of the ceramic membrane is highest. When the mass concentration of NH₄VO₃ is 5 g/L, the corrosion resistance of the ceramic membrane is best.