零污水排放镁合金化学镀镍沉积机制及Ni-P镀层的耐蚀性

摘要

对传统镁合金化学镀工艺进行改进，分析“零污水排放”化学镀镍新工艺的沉积机制。并以316L 不锈钢作为对比材料，研究该化学镀镍层的耐蚀性能。结果表明：新工艺获得的 Ni-P 镀层具有非晶结构，且组织均匀致密；在20%H2SO4溶液中，镀态和经200℃热处理的镀层的耐蚀性均优于316L不锈钢的；Ni-P镀层与316L不锈钢在20%H2SO4溶液中的动电位极化曲线对比表明，Ni-P镀层具有更正的腐蚀电位，可对AZ91D镁合金起到有效的保护作用。氟化镁转化膜在镀液中是稳定的，化学镀后与镀镍层和镁合金基体间的界面结合良好。%Traditional process of electroless Ni-P plating on AZ91D magnesium alloy was improved, and the deposition mechanism of a new wastewater-free electroless nickel plating was investigated. Meantime, the corrosion resistance of the Ni-P coating was studied using stainless steel 316L as contrast material. The results show that the Ni-P coating prepared with the new process is amorphous, and its microstructure is compact and uniform. The corrosion resistance of both as-plated and heat-treated Ni-P coating at 200℃is superior to that of stainless steel 316L in 20%H2SO4 solution. The potentiodynamic polarization curves in 20%H2SO4 solution indicate that the Ni-P coating has more positive corrosion potential than that of stainless steel 316L, and can provide good protection to magnesium alloy substrate. The MgF2 conversion film on the surface of magnesium alloy is stable in the bath. Good interface coherences, both in Ni-P coating-MgF2 film and in magnesium alloy matrix-MgF2 film, are formed.