热镀锌板三价铬钝化剂的制备及其钝化膜耐蚀性能  

Preparation and Corrosion Resistance of Trivalent Chromium Passivation Agent on Hot Dipped Galvanized Steel

作　　者：李军伟[1] 衣守志[1] 冯瑞沁 闫婷婷[1] 艾青[1] 

机构地区：[1]天津科技大学,天津300457

出　　处：《表面技术》2014年第2期109-113,133,共6页Surface Technology

摘　　要：目的制备钝化膜耐蚀性良好的热镀锌板三价铬钝化剂。方法以铬酸酐、酒石酸盐、无机混酸、纳米硅溶胶为原料,制备三价铬钝化剂。采用该钝化剂对热镀锌板进行钝化处理,通过中性盐雾试验、Tafel极化曲线和交流阻抗谱分析钝化膜的耐蚀性能,并表征钝化膜的表面形貌和元素组成。结果钝化镀锌板经120 h中性盐雾试验后,腐蚀面积仅为5%。与未钝化镀锌板相比,钝化试样的自腐蚀电位有所正移,自腐蚀电流密度降低了约2个数量级。钝化膜表面较为平整,有少量白色颗粒沉积,膜中主要含有C,O,Si,Cr,Zn等元素,且Cr主要以三价和六价存在,Zn以二价存在。结论该三价铬钝化剂可提高镀锌板的耐蚀性能,具有较好的工业使用推广价值。Objective To study the preparation of trivalent chromium passivation agent and its corrosion resistance. Methods A kind of trivalent chromium passivation agent was prepared on the surface of galvanization with background film-former（ a chromium anhydride）, reducing agent（ tartaric acid sodium）, additive（ inorganic mixed acid） and hole sealing agent（ nano silica）. The cor- rosion resistance of the passive film was studied by neutral salt spray test （NSS）, tafel polarization and ac impedance （EIS） tests; and the surface morphology and elemental composition of passive film were analyzed by scanning electron microscopy （ SEM ） and energy spectrum analyzer （EDS）. Results The results showed that the corrosion area of 120 h NSS experiment was below 5%. Compared with the corrosion potential（ 1. 015 V） of the galvanized sheet without passivation, the self-corrosion potential （0. 965 V） had positive displacement, and the corrosion current density decreased by about two orders of magnitude, from 8. 458 x 10-4 A/ em2 to 6. 356x10-6 A/cm2. The corrosion resistance of galvanized sheet after passivation was greatly increased. SEM test showed that membrane surface was smoother with white particle deposition ; EDS experiment indicated that passivated membrane mainly contained C, O, Si, Cr and Zn. XPS showed the Cr compounds were mainly trivalent and hexavalent, while the zinc compounds were mainly bivalent. Conclusion The passivation agent could improve the corrosion resistance of the galvanized sheet and has great industrial value.

关 键 词：热镀锌板 三价铬钝化 硅溶胶 耐蚀性 

分 类 号：TG174.45[金属学及工艺—金属表面处理]