(1. 厦门理工学院 材料科学与工程学院，厦门 361021；
2. 华南理工大学 材料科学与工程学院，广州 510640)
摘 要: 通过磷化/硝酸铈封闭后处理技术在镀锌层表面形成复合膜以提高其耐蚀性能。采用SEM、EDS、XPS和XRD研究复合膜的显微组织、化学成分、元素价态和相组成，并从热力学角度探讨复合膜的生长机理。结果表明：磷化镀锌层经硝酸铈封闭处理后，针片状磷化膜的间隙被铈盐膜覆盖，形成了连续完整的复合膜；在封闭过程中，部分磷化膜发生溶解，针片状磷化膜的边缘变得粗糙模糊，溶解的磷酸根离子又与Ce3+结合，生成不溶的水合磷酸铈，覆盖在复合膜表面，其中一部分水合磷酸铈与复合膜牢固结合，一部分为絮状疏松且可被漂洗下来；延长封闭时间，溶解的磷化膜增多，絮状化合物也增多并几乎覆盖整个复合膜表面；复合膜中含有Zn3(PO4)2·4H2O、CePO4·xH2O、CeO2和Ce(OH)4。
关键字: 镀锌层；复合膜；磷化膜；硝酸铈；封闭；生长机理
（1. School of Materials Science and Engineering, Xiamen University of Technology, Xiamen 361021, China;
2. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China）
Abstract:To enhance the corrosion resistance of galvanized steel, a composite coating was formed by phosphating and cerium nitrate post-sealing treatment. The microstructure, chemical composition, element valence and phase of the composite coatings were investigated by SEM, EDS, XPS and XRD. And the growth mechanism of the composite coating was discussed based on thermodynamics. The results show that after post-sealing the phosphated galvanized steel with cerium nitrate, the gaps of the needle-like zinc phosphate crystals are covered with cerium salts, and thus, the continuous and intact composite coatings form. During post-sealing process, the edges of phosphate crystals become rough and fuzzy due to the dissolution of phosphate. The dissolved phosphate ions simultaneously combine with cerium ions, and the corresponding insoluble CePO4·xH2O compounds form and cover on the composite coatings. A part of compounds bond strongly, and the other parts are flocculent and will be rinsed easily. Both the dissolved zinc phosphate and the new-formed flocculent compounds increase with the increase of post-sealing time, and finally the flocculent compounds almost completely cover the composite coatings. The composite coatings are composed of Zn3(PO4)2·4H2O, CePO4·xH2O, CeO2 and Ce(OH)4.
Key words: galvanized steel; composite coatings; phosphate coatings; cerium nitrate; post-sealing; growth mechanism
