ZM5镁合金无铬前处理化学镀镍层的性能

采用优化的Na4P2O7+Na2SO4+NaNO3体系的化学蚀刻无铬前处理化学镀镍工艺,在ZM5镁合金上制备Ni-P镀层。利用扫描电镜、能谱仪、X射线衍射仪分析镀层的微观形貌、成分和相结构。通过电化学方法和摩擦磨损试验评价了镀层的耐蚀性和耐磨性。结果表明:无铬前处理工艺制备的镀层中P的质量分数为12.90%。与ASTM标准的含铬前处理工艺得到的镀层的耐蚀性和耐磨性相比,无铬前处理得到的镀层的自腐蚀电位为-0.506V,腐蚀电流密度为2.132×10-6 A/cm2,接近ASTM工艺含铬前处理得到的镀层的耐蚀性能;同时其磨损率为3.056×10-4 mg/s,与ASTM工艺的1.778×10-3 mg/s相比,其抗摩擦磨损性能明显优于含铬前处理的镀层。无铬前处理化学镀镍显著提高了ZM5镁合金的耐蚀性和耐磨性。

Properties of Coating on ZM5 Magnesium Alloy Prepared by Chromium Free Electroless Nickel Plating

NiP plating was prepared on ZM5 magnesium alloy adopting chromium free Na₄P₂O₇+Na₂SO₄+NaNO₃ chemical etching pretreatment. The micro morphology, composition and phase structure of the coatings were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Xray diffraction (XRD). The results show that the mass fraction of phosphorus of the coating prepared by chromium free process is 12.90%.The corrosion and wear resistance of the coatings prepared by chromium free process and ASTM process were evaluated by electrochemical methods and ballondisc wear test. The results show that the corrosion potential and corrosion current density of the coatings prepared by the chromium free process are -0.506 V and 2.132×10^-6 A/cm², respectively. The corrosion resistance is close to the coating prepared by ASTM process. The wear loss rates of coatings prepared by chromium free process and ASTM process are 3.056×10^-4 mg/s and 1.778×10^-3 mg/s, respectively. The wear resistance of chromium free process is obviously higher than that of ASTM process. The coating prepared by chromium free process can provide favorable corrosion and wear resistance for ZM5 magnesium alloy.