热镀锌钢上铈盐转化膜在含Cl-介质中的耐蚀性

Corrosion Resistance of Cerium Salt Conversion Film on Hot-dip Galvanized Steel in Aqueous Chloride Media

将热浸镀锌钢浸渍在20 g·L^(-1)Ce(NO_3)_3·6H_2O溶液(pH=4,25℃)中10s^24 h,制备了铈盐转化膜试样。通过中性盐雾和盐水浸泡试验评价了转化膜在含Cl^-介质中的耐蚀性能。采用扫描电镜和X射线衍射能谱研究了转化膜的形貌和物相结构。结果表明,铈盐转化膜能显著推迟热浸镀锌层出现白锈的时间;随成膜时间的延长,转化膜的耐蚀性能先增加后下降;当成膜时间为30~60 min时,转化膜的耐蚀性能最佳。铈盐转化膜主要由非晶态结构的ZnO和CeO_2组成,在腐蚀介质中不易形成腐蚀微电池。

The cerium conversion film on hot-dip galvanized （HDG） steel sheets was prepared by chemical conversion in 20 g· L^-1 Ce （NO3）3-6H20 solution （pH=4, 25 ℃） for 10 s-24 h. The corrosion resistance of the galvanized steel coated with cerium conversion film was evaluated by the neutral salt spray （NSS） test and salt water immersion test in aqueous chloride media. The surface morphology and physical phase structure of the conversion film were investigated by means of SEM and XRD. The results show that the cerium conversion film can markedly prevent galvanized steel sheets from white rusting in comparison with the blank galvanized steel, the corrosion resistance of the cerium conversion film initially increases and then decreases with the increase of treatment time. The film prepared in the solution for 30 min-60 min exhibits the optimum corrosion resistance. The cerium salt conversion film mainly consists of amorphous ZnO and CeO2. It isn＇t easy for the film to form micro corrosion battery in corrosive media.