碱活化对镁合金化学镀Ni-P镀层形貌与性能的影响

Influence of Alkali Activation on Morphology and Properties of Electroless Ni-P Coating on Magnesium Alloy

研究了碱活化工艺中焦磷酸盐、碳酸钠及活化温度对化学镀Ni-P镀层形貌与性能的影响,并采用扫描电镜和电化学工作站对典型试样的形貌及耐蚀性进行了分析。最佳的碱活化工艺条件为:焦磷酸盐140~200g/L,碳酸钠15~35g/L,添加剂适量,活化温度80℃,活化时间2min。未经碱活化的镀层粗糙、孔隙明显;而经碱活化的镀层表面较平整、均匀,无明显缺陷,具有典型的胞状或球状形貌。碱活化镀层的自腐蚀电流密度为1.38×10^(-6) A/cm^2,仅为未经碱活化镀层的15.5%。

The influences of pyrophosphate, sodium carbonate and activation temperature of alkali activation on the morphology and properties of electroless Ni P coating were studied, and the morphology and corrosion resistance of typical sample were analyzed by scanning electron microscope and electrochemistry workstation. Results showed that the optimal alkali activation process conditions were as follows： pyrophosphate 140~200 g/L, sodium carbonate 15~35 g/L, appropriate amount of additive, activation temperature 80 ℃, activation time 2 min. The coating without alkali activation was rough with many pores, while the coating with alkali activation possesses smooth and even surface without obvious defects, and shows typical cellular or spherical morphology. The self corrosion current density of the coating with alkali activation was 1.38 × 10^-6 A/cm^2 , only 15.5 % of the self corrosion current density of the coating without alkali activation.