Objective To improve the corrosion resistance of the aluminum alloy drill pipe in offshore platform. Methods In this paper, the alumina ceramic membrane was prepared on the surface of 2A12 aluminum alloy for drill pipe in offshore platform by micro arc oxidation(MAO)technology. The effect of negative voltage on the corrosion resistance of MAO coatings was studied by salt spray test, and the microstructure and microstructure of MAO coatings were analyzed by scanning electron microscope and optical microscope. Results The negative voltage had a great influence on the preparation of MAO coating during the process of micro arc oxidation. The pore size of micro arc oxidation coating decreased with the increase of negative voltage, and the film surface became smoother. In addition, the content of Al2 O3 phase increased with the increase of negative voltage within a certain negative voltage range. When the negative voltage reached a limit value, the negative voltage increased with the decrease of Al2 O3 . The corrosion resistance of MAO coating could be improved as negative voltage increased. When the negative voltage was 8 V, the corrosion rate decreased from 0. 005 68 g / (dm2 ·h) to 0. 000 28 g / (dm2 ·h), which was 20 times higher than that at 24 V. When the negative voltage was 4 V, part of the coating was peeled off, and the corrosion was serious. When the negative voltage was increased to 24 V, the corrosion resistance of micro arc oxidation coating was effectively improved. Conclusion During the micro arc oxidation process, negative voltage had a great influence on the preparation of micro arc oxidation film. The corrosion resistance of micro arc oxidation could be effectively improved by increasing the negative voltage. In addition, Fe, S and other impurities in the matrix were the main factors that affected the corrosion resistance of micro arc oxidation coatings.