压铸镁合金植酸转化处理中添加剂的研究

压铸镁合金植酸转化处理中添加剂的研究/宋东福等压铸镁合金植酸转化处理中添加剂的研究*宋东福' ,赵雅情',戚文军',梁涛’,农登l(1 广州有色金属研究院材料加工研究所,广州510650; 2广州市机械科学研究院有限公司,广州510700)摘要通过在植酸基础转化液中添加两种不同组成的成膜促进剂制备镁合金植酸转化膜，采用SEM、EDS及失重法研究了添加剂对转化膜结构、形貌及耐蚀性能的影响。结果表明:经植酸转化处理后,镁合金表面耐蚀性能均得到了大幅提高，120 h盐水浸泡后失重率仅为镁合金基材的1/5;Ca(NO3)z、NH,VO3及NaC.HO%●2H2O组合添加剂的加入有利于改善膜层结构和致密性,转化膜由完整、致密且与基材结合紧密的内层和网纹的外层组成,耐蚀性能较纯植酸转化膜提高1倍,而NaF、Nar: BO及NaeCH4O%●2H2O的组合添加剂则对转化膜结构和耐蚀性能影响不显著。关键词镁合金添加剂植酸转化膜 失重率中图分类号:TG178文献标识码:AStudy on Additives in Phytic Acid Treatment for Diecasting Magnesium AlloySONG Dongfu'，ZHAO Yaqing'，QI Wenjun'，LIANG Tao2，NONG Deng'(1 Material Processing Institute ,Guangzhou Research Institute of Non- ferrous Metals,Guangzhou 510650;2 Guangzhou Mechanical Engineering Research Institute CO. ,LTD, Guangzhou 510700)AbstractTwo different kinds of phytic acid conversion coatings on magnesium alloy were prepared in phyticacid base conversion solution with accelerants. The effect of additives on the structure, morphology and corrosion re-sistance of conversion coating were investigated by SEM, EDS and weight loss method, respectively. The results showthat the magnesium alloy surface corrosion performance is improved substantially through phytic acid conversion treat-ment, and the weight loss of conversion coating is only 1/5 of the magnesium alloy substrate after 120 h saline soa-king. The structure and compactness of conversion coating are greatly improved by adding Ca(NOz)z ,NH VO3 andNa2C. H,O%●2H2O, as the conversion coating consists of inner layer which is combined with the substrate compactlyand outer layer which exhibits overlapping curve. The corrosion resistance of corversion coating increases 100% com-pared to pure phytic acid conversion coating. However, other additives such as NaF,Naz BO and Na2CH4O%●2H2Ohave no significant impact on structure and corrosion resistance of phytic acid conversion coating.Key words magnesium alloy, additive, phytic acid conversion coating, weight-loss ratio镁及镁合金具有比强度和比刚度高、铸造性能好、电磁等6种有毒有害物质的RoHS指令。拥有百年历史的金属屏蔽和阻尼性能良好及可回收利用等优点,广泛应用于航空表面铬酸盐处理传统工艺受到限制,开发其替代工艺迫在眉航天、汽车摩托车、电动工具、电子通讯、光学仪器、计算机等睫,在这样的形势下,镁合金低成本、环境友好型无铬转化工领域”。但耐蚀性差成为了制约镁合金应用于苛刻领域的艺,如高锰酸盐、钼酸盐.锡酸盐、钴酸盐、有机转化膜、稀土三大技术瓶颈之- _[C。 为了改善镁合金表面的耐蚀性能,许等体系8-1]成为各国研究的热点。多防护处理方法相继被开发出来,如化学转化、阳极氧化、微植酸是废弃谷壳的提取物,其分子中含有6个磷酸基，弧氧化、金属覆层、气相沉积以及有机涂层等13-1 ,其中化学是一种少见的金属多齿螯合剂。当其与金属络合时,易形成转化法因具有工艺简单、成本低廉、不受工件形状和尺寸的多个整合环,且所形成的络合物稳定性极强。同时,植酸膜影响以及与有机涂层结合力强等优点0:1]而备受青睐。最早表面富含羟基和磷酸基等有机官能团,对提高镁合金表面涂应用于工业化生产的转化膜是铬酸盐系列，以美国的DOW装的附着力进而提高其耐蚀性具有非常重要的意义。崔秀公司开发的一系列处理液为代表,该法工艺成熟，所得转化芳等[1]采用纯植酸溶液制备的镁合金植酸转化膜覆盖度高，膜性能优良,在第二次世界大战期间得到了大规模的应用，无开裂现象,成膜后自腐蚀电流密度降低6个数量级,大幅但处理液中含有毒的Cr离子,对人体和环境危害极大,欧盟提高了AZ91D镁合金的耐蚀性。郑润芬等[4 -16]也通过实验已于2003年通过了关于在电气电子设备中限制使用六价铬得到了类似的中国煤化工中于纯植酸溶液条YHCNMH G*广东省粤港关键领域重点突破项目(2010A090604001);广东省重大科技专项(zv1IAvOU4UUU5;宋东福:男,1984年生,硕士,工程师,主要从事轻合金加工与成型技术研究Tel:020-37238039 E-mail:375462908@qq. com.●102●材料导报B:研究篇2013年10月(下)第27卷第10期(2)Ca(NO2)2、NH,VO3及Na2CHO。●2H2O组合添magnesium based metal matrix composites []. 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