热镀锌钢铈盐/硅烷复合膜的制备及其耐蚀性能

Preparation and Corrosion Resistance Evaluation of Cerium Salt/Silane Composite Coating on Hot-Dip Galvanized Steel

热镀锌钢板上单一的铈盐、硅烷钝化膜有一些缺点,对提高其耐蚀性作用不大。为此,将热镀锌钢板先经铈盐溶液处理,再用乙烯基三甲氧基硅烷溶液浸渍,获得了铈盐/硅烷复合钝化膜。采用扫描电镜(SEM)、俄歇电子能谱(AES)、盐水全浸试验和电化学交流阻抗谱(EIS)研究了复合膜层的表面形貌、结构特性和耐蚀性能。结果表明:硅烷膜能较好地填充铈盐转化膜中的裂纹,铈盐/硅烷复合膜层连续、完整、致密,厚400～450 nm,与基体结合较好,复合膜中硅烷膜/铈盐转化膜/锌基体的化学成分呈连续的梯度变化;与热镀锌钢相比,单一铈盐转化膜、硅烷膜的交流阻抗值增加了1个多数量级,复合膜的则增加了约2个数量级,复合膜层的耐蚀性较单一膜层显著增强,且优于常规铬酸盐钝化膜。

Hot-dip galvanized steel was firstly treated in the solution of cerium nitrate and then immersed in vinyltrimethoxysilane solution to obtain composite coating consisting of cerium salt coating and silane coating.The morphology and microstructure of as-obtained composite coating were analyzed by scanning electron microscopy and Auger electron spectroscopy,and its corrosion resistance was evaluated based on immersion test in salt water and electrochemical impedance spectroscopic analysis as well.Results showed that the microcracks in the cerium conversion coating could be well filled up with the silane coating.As-obtained cerium salt/silane composite coating with a thickness of 400~450 nm was continuous,complete and compact,and had good adhesion to the steel substrate as well as gradient chemical composition.In the meantime,the electrochemical impedance values of the cerium conversion coating and silane coating were increased by more than one order of magnitude as compared with that of hot-dip galvanized steel substrate,and the electrochemical impedance value of the cerium salt/silane composite coating was increased by about two orders of magnitude.In one word,as-obtained cerium salt/silane composite coating possessed much better corrosion resistance than single cerium salt conversion coating or silane coating as well as conventional chromate conversion coating.