AZ31B镁合金表面植酸改性V/Zr转化膜的耐蚀性  

Corrosion Resistance of Phytic Acid-Modified V/Zr Conversion Coating on AZ31B Mg Alloy

作　　者：蒋书琴[1] 郭瑞光[1] 蒋晓[1] 

机构地区：[1]西安建筑科技大学西北水资源与环境生态教育部重点实验室,陕西西安710055

出　　处：《材料保护》2015年第6期24-27,44,共5页Materials Protection

基　　金：国家自然科学基金项目(20976143);教育部高等学校博士学科点专项科研基金(20096120110007)资助

摘　　要：为了进一步提高镁合金表面V/Zr转化膜的耐蚀性,在转化液中加入植酸,在AZ31B镁合金表面制备了植酸改性V/Zr转化膜。采用扫描电镜、能谱分析、傅里叶红外光谱、中性盐雾试验、电化学测试及厚度仪分析了转化膜的性能,并对转化液配方及工艺条件进行了优选。结果表明:转化液最佳配方为3.0 g/L偏钒酸钠,2.0 g/L氟锆酸钾,1.0 m L/L植酸;最佳工艺参数为温度50℃,p H值2.0,时间15 min;植酸改性后转化膜主要由C,P,O,F,Mg,Al,V,Zr元素组成,呈无定形结构,耐中性盐雾时间为140 h,较改性前增加了60 h,其腐蚀电位较改性前正移了91 m V,自腐蚀电流密度减小了1个数量级,膜厚较改性前增加2.73μm,转化膜耐蚀性显著提高。Phytic acid was added into the V/Zr conversion fluid of AZ31 B Mg alloy so as to prepare V/Zr conversion coating with improved corrosion resistance.The morphology,composition and chemical structure of the as- prepared V/Zr conversion coating were analyzed by scanning electron microscopy,energy dispersive spectrometry and Fourier transform infrared spectrometry.The corrosion resistance of the V/Zr conversion coating was evaluated with a neutral salt-spray test rig and an electrochemical test rig,and the conversion bath and condition for fabricating V/Zr conversion coating were optimized.Results showed that the conversion fluid exhibited optimal composition of 3.0 g/L sodium metavanadate,2.0 g/L potassium fluorozirconate and 1.0 mL/L phytic acid,while the optical processing parameters for fabricating the conversion coating were suggested as a temperature of SO℃,a pH value of 2.0 and a conversion time of 15 min.Asprepared phytic acid-modified V/Zr conversion coating consisted of C,P,O,F,Mg,Al.V and Zr,and it exhibited amorphous structure.Besides,the modified conversion coating was able to endure neutral salt-spray for up to 140 h(increased by 60 h as compared with the unmodified conversion coating),while its corrosion potential positively shifted by 91 mV and its corrosion current density declined by one order of magnitude as compared with the unmodified counterpart.Modification by phytic acid helped to significantly improve the corrosion resistance of the V/Zr conversion coating.

关 键 词：V/Zr转化膜 镁合金 植酸改性 耐蚀性 

分 类 号：TG174.4[金属学及工艺—金属表面处理]