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For solving the problems of poor structural stability and machining difficulties of non-metallic insulating rings in space conductive slip rings, Al₂O₃ ceramic coatings were deposited on 2A12 aluminum alloy substrate by atmospheric plasma spraying technology to replace non-metallic insulating materials, and the phase composition, microscopic morphology, microhardness, bonding strength, and insulation performance of the coating were studied. Results showed that the main phase of Al₂O₃ spherical powder prepared by agglomeration sintering of original nanoparticles was α-Al₂O₃. After spraying, Al₂O₃ in the coating existed as α phase and γ phase, and the coating bonded well with the substrate, and the porosity of the coating was relatively lower. Moreover, the as-prepared coating had a uniform and dense microstructure, with no obvious macroscopic cracks or large pores inside the coating. Although no sealing treatment was used, the coating still presented high insulation performance in insulation resistance tests with a DC voltage of 1 000 V in atmospheric environments, which could meet the service requirements of space conductive slip ring insulating rings.