AZ91D压铸镁合金表面最佳硅烷成膜工艺及其耐蚀性能  

Optimization of Technology for Preparing Silane Coating on Magnesium Alloy and Evaluation of Corrosion Resistance of the Coating

作　　者：吴海江[1] 徐国荣[2] 许剑光[1] 徐红梅[1] 吴玉蓉[1] 颜焕元[1] 

机构地区：[1]湖南科技大学高温耐磨材料及制备技术湖南省国防科技重点实验室,湖南湘潭411201 [2]湖南科技大学化学化工学院,湖南湘潭411201

出　　处：《材料保护》2013年第9期32-34,56,共4页Materials Protection

基　　金：湖南省自然科学基金资助项目(10JJ6084)

摘　　要：过去,对AZ91D压铸镁合金表面硅烷化的报道较少。以耐点蚀性能为指标,采用正交试验法优选了AZ91D压铸镁合金表面制备γ-氨丙基三乙氧基硅烷(KH-500)膜的主要工艺参数,包括硅烷体积分数、乙醇与去离子水体积比、水解时间、溶液pH值和浸涂时间等;通过盐水全浸试验考察了优化工艺条件下所得硅烷膜的耐蚀性能,利用扫描电镜(SEM)和能谱仪(EDS)分析其表面形貌和组成。结果表明:影响AZ91D压铸镁合金表面KH-550硅烷成膜因素的主次顺序为溶液pH值>水解时间>乙醇与去离子水体积比>硅烷体系分数>浸涂时间;最佳成膜工艺条件为硅烷体积分数为5%,乙醇与去离子水体积比为85∶15,水解时间为2 h,pH值为9,浸涂时间90 s;以最佳工艺制备的KH-550硅烷膜自然干燥后不太均匀,膜主要由C,N,O,Mg,Al,Si等元素组成,其防护能力略优于常规低铬钝化膜,可显著改善镁合金基体的耐蚀性能。Orthogonal experiments were carried out to determine the optimized bath composition and parameters( volume fraction of silane,ratio of ethanol to deionized water,hydrolysis time,pH value of silane solution and immersion time) for preparing KH-550 silane coating on die casting magnesium alloy AZ91D. The corrosion resistance of the silane coating obtained under the optimal conditions was evaluated based on complete immersion test in neutral salt water. The morphology and composition of the silane coating were analyzed by means of scanning electron microscopy and energy dispersive spectrometry. Results indicated that,in terms of the effect on the film-formation of silane coating,various factors could be ranked as solution pH value > hydrolysis time > volume ratio of ethanol to deionized water > volume fraction of silane > immersion time. The optimized parameters were suggested as silane volume fraction of 5%,ethanol to deionized water volume ratio of 85 ∶ 15,hydrolysis time of 2 h,solution pH value of 9, and immersion time of 90 s. Resultant silane coating consisted of C,N,O,Mg,Al,and Si. Particularly,as-prepared silane coating had better shielding ability than traditional low chromate passivation coating,and it could significantly improve the corrosion resistance of the Mg alloy substrate.

关 键 词：γ-氨丙基三乙氧基硅烷(KH-500)膜 耐蚀性 AZ91D镁合金 正交试验 

分 类 号：TG174.4[金属学及工艺—金属表面处理]