目的 为提高镁合金化学镀Ni-P合金镀层的腐蚀防护性能。方法 在AZ31B镁合金表面，先化学镀Ni-Cu-P，再化学镀Ni-P，制备Ni-Cu-P/Ni-P复合镀层。研究复合镀层的表面形貌、成分、厚度和腐蚀电流密度随镀液硫酸铜浓度的变化规律，表征1.0 g/L硫酸铜质量浓度下，复合镀层的截面形貌、成分和晶态结构。结合动电位极化曲线和盐雾试验，分析复合镀层的耐蚀性能和腐蚀防护机理。结果 复合镀层中的铜含量随硫酸铜浓度的增加而升高，铜对复合镀层的结构和性能影响很大。通过抑制镀层表面胞状物的生长和增加形核点数量，铜的共沉积能够大幅提高复合镀层的致密性。随硫酸铜浓度的增加，样品表面的催化活性下降，镀液稳定性升高，由此导致复合镀层的厚度随硫酸铜浓度的增加而明显下降。硫酸铜质量浓度为1.0 g/L时，复合镀层均匀致密，并具有可钝化性，按照ISO 9227，其耐盐雾腐蚀时间超过180 h。结论 化学镀Ni-Cu-P/Ni-P复合镀层能够赋予镁合金表面优异的耐蚀性能，复合镀层所具有的可钝化性和均匀致密的镀层结构，是镀层腐蚀防护性能提升的主要原因。

The work aims to improve the anti-corrosion properties of the electroless Ni-P coatings on magnesium alloys. Ni-Cu-P/Ni-P composite coatings were prepared by plating Ni-Cu-P and Ni-P on AZ31B magnesium alloys. The change rules of surface morphologies, compositions, thicknesses and corrosion current densities of the composite coatings along with the CuSO4 concentrations in the bath solutions were studied. The cross-section morphology, compositions and crystal structure of the com-posite coating with CuSO4 concentration of 1.0 g/L were characterized. Potentiodynamic polarization curves and salt spray tests were conducted to investigate the anti-corrosion properties and mechanisms of the composite coatings. From the experimental results, the copper content in the composite coatings increased with the increasing CuSO4 concentrations, and copper had sig-nificant influences on the structures and properties of the composite coatings. The copper codeposition could enhance the com-pactness of the composite coatings to a large extent by suppressing the growth of the nodules and producing more nuclei. As the concentration of CuSO4 increased, the catalytic activity on the sample surface decreased and the stability of bath solution improved, which resulted in the obvious decrease in the coating thicknesses with the increasing CuSO4 concentrations. The composite coating with a CuSO4 concentration of 1.0 g/L was uniform, compact, and passivable, and the corrosion performance was found to withstand >180 h salt spray test in accordance with ISO 9227. Ni-Cu-P/Ni-P composite coatings can provide a superior corrosion resistance to the magnesium alloy substrates. The passivable and compact coating layers of composite coatings are main factors to improve the anti-corrosion properties.