CORROSION BEHAVIOR OF A ZIRCONIUM-TITANIUM BASED PHOSPHONIC ACID CONVERSION COATING ON AA6061 ALUMINIUM ALLOY

The conversion coating was formed by dipping AA6061 in a fluorotitanate/zirconate acid and amino trimethylene phosphonic acid （ATMP） solution at room temperature. The formation process and the anti-corrosion performance of the conversion coating were investigated using electrochemical test and salt spray test （SST）, respectively. The electrochemical test shows that the Zr/Ti and ATMP coating improves the corrosion resistance of AA6061 as good as the chromate （VI） coating. But the results of SST show that the corrosion resistance of Zr/Ti and ATMP coating is not as good as the chromate （VI） coating. The corrosion area is less than 2% after 72 h.

基于水性硅烷聚合物与Ti/Zr复合化学转化技术在多种金属表面的工艺研究

以6061铝合金、7075铝合金和镀锌钢为研究对象,通过优化一种水性环氧基硅烷聚合物与氟钛酸/氟锆酸复合化学转化工艺,同步提高了3种金属的耐腐蚀性能。采用电化学性能测试和硫酸铜点滴试验对膜层的耐腐蚀性能进行探讨,并结合扫描电镜(SEM)和能谱(EDX)对转化膜微观形貌及元素组成进行表征分析,最后探讨了钛锆硅烷复合转化膜的成膜机理。结果表明:当选择最优的工艺配方,即WB100水性硅烷2.7%、H_(2)TiF_(6)2.2 mL/L、H_(2)ZrF_(6)1.0 mL/L、转化时间90s、pH=3.7、温度40℃时,多种金属材料的复合转化膜表面均匀致密,具有较优的耐腐蚀性能。成膜机理分析表明,起始钛锆硅烷复合转化膜经3个阶段演变后,最终形成了由金属氧化物和有机单分子膜组成的双层膜结构。

钢热浸镀锌层氟钛酸–聚丙烯酸复合转化膜制备和表征

在以氟钛酸为成膜剂的转化液中添加聚丙烯酸(PAA),在热浸镀锌层上制备了氟钛酸–聚丙烯酸复合转化膜(简称H–P转化膜),获得了最佳成膜工艺:H2Ti F6(质量分数60%)5 m L/L,Mn(H2PO4)2·2H2O 15 g/L,PAA 10 m L/L,p H 2.5,处理时间1 min。通过扫描电镜(SEM)研究了复合转化膜成膜过程的表面形貌,采用能谱(EDS)、红外光谱(IR)和X射线光电子能谱(XPS)技术对膜层组成进行了表征。结果表明,PAA参与了成膜反应,所获得的H–P转化膜表面均匀致密,主要由Zn的氧化物、氟化物、磷化物,Ti的氧化物,Mn的氧化物以及聚丙烯酸盐类物质组成,其耐蚀性能比纯氟钛酸转化膜高。

Structural investigation of the zirconium-titanium based amino trimethylene phosphonate hybrid coating on aluminum alloy

A zirconium-titanium based amino trimethylene phosphonate hybrid coating on AA6061 aluminum alloys was formed by dipping in a fluorotitanate/zirconate acid and amino trimethylene phosphonic acid （ATMP） solution for improving the lacquer adhesion and corrosion resistance as a substitute of chromate coatings. The morphology and structure of the hybrid coating were studied by means of scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The surface composition and structure characteristics were also investigated by means of X-ray photoelectron spectroscopy （XPS） and Fourier transformation infra-red spectroscopy （FTIR）. The results of SEM and AFM show that the hybrid coating present piece particle distribution which is much denser than that of the zirconium-titanium coating. The results of XPS and FTIR indicate that the hybrid coating is a hybrid composite structure composed of both the zirconium-titanium and amino trimethylene phosphonate coatings.

热浸镀锌层氟钛酸转化膜的制备和耐蚀性能

以氟钛酸为成膜剂、磷酸二氢锰为促进剂对热浸镀锌层表面进行钝化处理,获得了氟钛酸转化膜。采用扫描电镜研究了不同处理时间所得转化膜的微观形貌;通过中性盐雾试验、电化学极化和电化学阻抗谱,研究了不同处理时间所得转化膜的耐蚀性。确定了氟钛酸转化膜的制备工艺条件为:H2TiF6(w=60%)5mL/L,Mn(H2PO4)2·2H2O15g/L,pH2.5,处理时间1min。与未经处理的热浸镀锌试样相比,经氟钛酸钝化后的试样在中性盐雾试验中出现白锈的时间明显延迟,在5%NaCl溶液中的腐蚀电流密度明显降低,极化电阻和电化学阻抗显著增大。处理时间为1min时所得转化膜的耐蚀性能最好。