Structure and effects of electroless Ni-Sn-P transition layer during acid electroless plating on magnesium alloys

镁合金酸性化学镀中化学镀Ni-Sn-P过渡层的结构与作用（英文）

An electroless ternary Ni-Sn-P transition layer with high corrosion resistance was applied for acid electroless nickel plating on magnesium alloys. The surface morphologies and microstructure of the traditional alkaline electroless Ni-P and novel Ni-Sn-P transition layers were compared by SEM and XRD, and the bonding strengths between the transition layers and AZ31 magnesium alloys were tested. The corrosion resistance of the samples was analyzed by porosity test, potentiodynamic polarization, electrochemical impedance spectroscopy（EIS） in acid electroless solution at p H 4.5 and immersion test in 10% HCl. The results indicate that the transition layer is essential for acid electroless plating Ni-P coatings on magnesium alloys. Under the same thin thickness（-6 μm）, the electroless Ni-Sn-P transition layer possesses superior properties to the traditional Ni-P transition layer, including high amorphization, smooth and dense surface without pores, enhanced bonding strength and corrosion resistance. Most importantly, acid electroless Ni-P coatings can be successfully deposited on magnesium alloys by using Ni-Sn-P transition layer.

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。