(1. 廈門理工學(xué)院 材料科學(xué)與工程學(xué)院，廈門 361021；
2. 華南理工大學(xué) 材料科學(xué)與工程學(xué)院，廣州 510640)
摘 要: 通過磷化/硝酸鈰封閉后處理技術(shù)在鍍鋅層表面形成復(fù)合膜以提高其耐蝕性能。采用SEM、EDS、XPS和XRD研究復(fù)合膜的顯微組織、化學(xué)成分、元素價態(tài)和相組成，并從熱力學(xué)角度探討復(fù)合膜的生長機理。結(jié)果表明：磷化鍍鋅層經(jīng)硝酸鈰封閉處理后，針片狀磷化膜的間隙被鈰鹽膜覆蓋，形成了連續(xù)完整的復(fù)合膜；在封閉過程中，部分磷化膜發(fā)生溶解，針片狀磷化膜的邊緣變得粗糙模糊，溶解的磷酸根離子又與Ce3+結(jié)合，生成不溶的水合磷酸鈰，覆蓋在復(fù)合膜表面，其中一部分水合磷酸鈰與復(fù)合膜牢固結(jié)合，一部分為絮狀疏松且可被漂洗下來；延長封閉時間，溶解的磷化膜增多，絮狀化合物也增多并幾乎覆蓋整個復(fù)合膜表面；復(fù)合膜中含有Zn3(PO4)2·4H2O、CePO4·xH2O、CeO2和Ce(OH)4。
關(guān)鍵字: 鍍鋅層；復(fù)合膜；磷化膜；硝酸鈰；封閉；生長機理
（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
