ZM6镁合金化学镀镍预处理工艺及镀层耐蚀性

Pretreatment process and corrosion resistance of electroless nickel plating on ZM6 magnesium alloy

采用浸锌预处理工艺,研究在碱式碳酸镍体系中ZM6镁合金表面化学镀镍层性能。用扫描电镜(SEM)、能谱仪(EDS)和X线衍射仪(XRD)研究浸锌层和镀镍层的形貌、成分及镀层结构,采用极化曲线测试镀层的耐蚀性。研究结果表明,浸锌溶液中加入Sn2+可在ZM6镁合金表面获得均匀致密的浸锌层,后续在碳酸镍体系中施镀1 h后所得非晶态Ni-P镀层均匀致密,无明显缺陷,厚度为8.74μm,磷质量分数达9.29%;在3.5%NaCl溶液中,镀层的自腐蚀电位为-0.609 V,腐蚀电流密度约为基体的1/10,耐腐蚀性能良好。

Nickel coating was prepared on ZM6 magnesium alloy by electroless nickel plating in nickel carbonate bath with pretreatment of zinc immersion. The morphology and composition of zinc coating and electroless nickel coating were studied by scanning electronic microscopy （SEM） and energy dispersive spectroscopy （EDS）. The structure of nickel coating was studied by X-ray diffraction spectroscopy （XRD）. Potentiodynamic polarization analysis was used to study the corrosion resistance of the coating. The results indicate that a compact, well-distributed zinc coating is obtained on the surface of ZM6 alloy in a new zinc immersion solution with addition of Sn^2＋. The subsequent amorphous electroless nickel coating is uniform and the thickness is 8.74 μm after 1 h deposition. Phosphorus mass fraction is 9.29% The corrosion potential is -0.609 V, and the corrosion current density is about 1/10 of substrate in 3.5% NaC1 solution.