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将具有高耐蚀性的化学镀Ni-Sn-P三元合金过渡层应用于镁合金酸性化学镀镍过程。通过SEM和XRD对比研究传统碱性化学镀Ni-P过渡层与新型Ni-Sn-P过渡层的表面形貌和显微组织,并测试过渡层与AZ31镁合金之间的结合力。采用孔隙率、过渡层在p H=4.5的酸性化学镀镍溶液中的动电位极化曲线和电化学交流阻抗(EIS)以及10%HCl浸泡实验研究过渡层的耐蚀性。结果表明:过渡层对于直接在镁合金表面进行酸性化学镀Ni-P合金是必不可少的。在相同厚度(~6μm)条件下,与传统化学镀Ni-P过渡层相比,化学镀Ni-Sn-P过渡层的非晶化程度更高,表面平整致密,镀层无孔隙,结合力强,耐蚀性更高。最重要的是,以化学镀Ni-Sn-P为过渡层可以成功地在镁合金表面制备酸性化学镀Ni-P合金镀层。
The electroless Ni-Sn-P ternary alloy transition layer with high corrosion resistance is applied to the acid electroless nickel plating process of magnesium alloy. The surface morphologies and microstructures of the conventional alkaline electroless Ni-P transition layer and the novel Ni-Sn-P transition layer were studied by SEM and XRD. The bonding between the transition layer and the AZ31 magnesium alloy was also tested. The corrosion resistance of the transitional layer was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in the electroless nickel plating solution with pH = 4.5 and 10% HCl immersion test. The results show that the transition layer is indispensable for the acidic electroless Ni-P alloy coating directly on the surface of magnesium alloy. Under the same thickness (~ 6μm), the electroless Ni-Sn-P transition layer has higher degree of amorphization than the traditional electroless Ni-P transition layer, the surface is smooth and dense, the coating has no porosity, and the bonding strength is strong , Corrosion resistance is higher. Most importantly, the acidic electroless Ni-P alloy plating can be successfully prepared on the surface of magnesium alloy by electroless Ni-Sn-P as transition layer.