钢铁表面纯锆盐转化膜技术研究现状与进展

Research Status and Progress of Pure Zirconium Salt Conversion Coating Technology Applied on Steel Surface

锆盐转化膜技术是一种十分重要的环境友好型钢铁表面处理技术,有望完全取代磷酸盐和铬酸盐转化技术。锆盐转化膜的耐蚀性与磷酸盐和铬酸盐转化膜接近,对有机涂层和钢铁基体有着优异的附着力。从纯锆盐转化基本原理、锆盐体系选择、制备方法、转化工艺参数控制、膜层形貌与结构、膜层耐蚀行为、膜层与后续涂层的附着力等方面,对国内外钢铁表面纯锆盐转化膜技术的研究进展和成果进行了综述。纯锆盐转化技术采用的转化液以氟锆酸及其盐为主,制备方法主要是浸渍法。为了获得质量稳定的纯锆盐转化膜,需要控制工艺参数:Zr^(4+)体积分数3%~5%,pH值3.5~4.5,转化时间90 s左右,温度20~35℃。锆盐转化膜一般为100~350 nm厚的双层结构,由纳米颗粒、小结节和聚集体构成,这种结构发挥的锚固作用会显著增加基体与后续涂层的结合强度。但是,锆盐转化成膜机理不够成熟,工艺欠稳定,在实际工业生产应用中仍面临挑战。所以,成膜机制和工艺稳定性的深入探究是未来锆盐转化膜的重点研究方向。

As one of vital and environment-friendly surthce treatment technologies applied on the steel surface, Zirconium salt conversion coating technology is expected to completely replace phosphate and chromate conversion technologies. The zirconium salt conversion coating exhibited high corrosion resistance which was almost comparable with that of conventional phosphate and chromate conversion coatings. In addition, it exhibited excellent adhesion to steel and organic coating. Research progress and achievements on zirconium salt conversion technologies applied on steel surface at home and abroad were reviewed in aspects including basic principle of zirconium salt conversion, selection of zirconium salt, preparation method, conversion process parameter control, coating morpholo- gy and structure, coating anti-corrosion behavior and adhesion to subsequent coating. Zirconium conversion film was usually prepared in dipping method and its conversion solution was mainly composed of hexafluorozirconic acid and its salts. In order to obtain high-quality conversion film, process parameters as follows should be controlled： [Zr4＋] should be 3%-5%, pH 3.5-4.5, t≈90 s and temperature 20-35 ℃. Zirconium conversion coating was generally a 100-350 nm thick two-layered structure consisting of nano par- ticles, small nodules and clusters. Anchoring effect of the structure could significantly improve the adhesion between substrate and sub- sequent coating. However, the zirconium salt conversion technology is still confronted with some challenges in the practical industrial production applications due to its underdeveloped conversion mechanism and unstable conversion process. Thcrelbre, thorough inves- tigation of film-forming mechanism and process stability were the focus of research on zirconium salt conversion film in the future.