AZ31镁合金轧态薄板化学镀Ni-P合金的工艺研究

Investigation of Electroless Ni-P Alloy Plating Process on Rolling Sheet of AZ31 Magnesium Alloys

为了改善AZ31镁合金轧态薄板的耐腐蚀性能，通过正交试验优化了化学镀Ni-P的配方及工艺，并对Ni-P镀层的形貌、镀层厚度、镀层中P元素的含量以及镀层在3．5％NaCI溶液中的极化曲线进行了测试和表征。结果表明，AZ31镁合金化学镀Ni—P的最优方案为：碱式碳酸镍10g／L，次亚磷酸钠25g/L，温度80％，pH值=8。所得的Ni—P镀层均匀，无明显缺陷，厚度约为18～23μm，P元素的质量分数为9．68％。试样经化学镀Ni—P后的自腐蚀电位大幅度提高，出现了约600mV的钝化区间，其耐蚀性能明显提高。

The technology of electroless Ni-P plating on rolling sheet of AZ31 magnesium alloys was studied to improve the corrosion resistance of this alloy. And the best ratio and the process parameters of eleetroless Ni-P plating were optimized by the orthogonal design experiment. The morphology of the Ni-P coating was studied. The thickness of Ni-P coating was measured and the content of P in the coating was measured. And the polarization curve of the Ni-P coating was studied in 3.5 % NaCl solution. The results show that the best parameters of the orthogonal design experiment are NiCO3-3Ni（ OH）2·4H2O 10g/L; NaH2PO2·H2O 25g/L; Temperature 80℃ ; pH =8. The Ni-P coating obtained by the optimized parameters is even and don＇t have any defects. The thickness of the coating is about 18 - 23μm. The mass fraction of P in the coating is 9.68%. After electroless Ni-P plating, the corrosion potential of the sample increases and there is a passive zone which is about 600mV, so the corrosion resistance of this rolling sheet of AZ31 magnesium alloys has been improved significantly.