▎ 摘　　要

NOVELTY - Method for preparing black micro-arc oxidation film layer, involves (i) grinding surface of the magnesium alloy substrate with sandpaper, cleaning with acetone solution and deionized water, and blow drying, (ii) placing the treated magnesium alloy substrate in an electrolyte of silicate system, and adding potassium permanganate, EDTA, lanthanum (III) nitrate and graphene to the electrolyte, and (iii) adopting a bipolar pulse power supply, adjusting appropriate electrical and non-electrical parameters, and preparing a corrosion-resistant, dense and uniform black micro-arc oxide film on the surface of the metal substrate. USE - The method is used for preparing black micro-arc oxidation film layer (claimed) on AZ91D magnesium alloy surface doped with rare earth salt and graphene. ADVANTAGE - The method provides black micro-arc oxidation film layer having excellent corrosion resistance, wear resistance, hardness, hardness uniformity and compactness, and excellent bonding performance. The black film layer and the magnesium alloy bonding force of the film layer are enhanced. The film layer has excellent appearance, and has wide application range. The performance of magnesium alloy is improved, and the application range is made wider. The corrosion resistance of the black coating and the substrate is improved. The appearance of the substrate surface black color is uniform and pure, and metal surface to generate a compact ceramic coating is generated to improve the corrosion resistance and the performance of the metal substrate. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a magnesium alloy black micro-arc oxidation film layer comprising produced film layer which is pure and uniform in black, has high blackness, strong bonding force with the magnesium alloy matrix, excellent corrosion resistance and wear resistance, where the composition of the micro-arc oxidation film layer comprises magnesium oxide and forsterite with a spinel structure, and the substance that appears black on the surface is manganese oxide.