镁合金磷酸盐 /氮化硅双层复合膜结构及耐蚀性能研究

目的针对传统镁合金化学转化膜裂纹尺寸大、耐腐蚀性差等问题,制备一种镁合金磷酸盐/氮化硅双层结构的抗腐蚀复合膜。方法先对镁合金进行传统磷酸盐转化处理,再运用等离子体增强化学气相沉积技术沉积氮化硅膜层,分析复合膜的形貌、元素分布、表面电位及极化曲线,并与磷酸盐转化膜进行对比。结果氮化硅膜层能在磷酸盐转化膜裂纹处选择性优先沉积,从而在相当程度上填补转化膜层的裂纹,形成致密的复合膜结构。具有复合膜结构的镁合金表面电位和腐蚀电位明显高于传统磷酸盐转化处理的镁合金。结论镁合金表面制备磷酸盐/氮化硅双层复合膜后,抗腐蚀能力明显高于传统磷酸盐转化处理的镁合金。

Study on the Structure and Corrosion-resistant Performance of Phosphate/Silicon Nitride Double Composite Coating on Magnesium Alloy

Objective To solve the problems of traditional chemical conversion coatings on magnesium alloy such as large microcracks and poor corrosion resistance, a novel phosphate /silicon nitride compound coating was prepared in this article. Methods First traditional magnesium phosphate conversion treatment was conducted, and then plasma enhanced chemical vapor deposition technology was used to deposit silicon nitride film layer. The morphology, element distribution, surface potential and polarization curve of the composite coating were analyzed, and compared with those of the phosphate conversion coating. Results Silicon nitride film layer could be selectively priorly deposited on the cracking positions of the phosphate conversion coating, and filled the cracks on the conversion coating layer, forming dense composite coating structure. The surface potential and corrosion potential of magnesium alloy with composite coating structure were significantly higher than those of magnesium alloy treated with traditional phosphate conversion process. Conclusion After preparation of phosphate /silicon nitride double composite coating on the surface of magnesium alloy, the corrosion resistance was significantly higher than that of the magnesium alloy treated with traditional phosphate conversion.