镀锌钢上钼酸盐/硅烷复合膜的结构与耐蚀性

将热镀锌钢板用二步法（先后浸入钼酸盐钝化液和硅烷溶液）和一步法（一次浸入加有钼酸盐钝化剂的硅烷溶液）获得钼酸盐/硅烷复合膜，用XPS和AES对 2种复合膜的化学成分进行表面分析和剥层分析，用Tafel极化曲线测量和盐雾腐蚀试验（NSS）对膜层的耐蚀性能进行了研究，并将它们与单独的钼酸盐转化膜、硅烷膜对比。结果表明，由一步法制备的复合膜与二步法制备的复合膜具有相似的双层结构，内层以钼酸盐转化膜（含O、Mo、Zn、P）为主而外层以硅烷膜（含C、O、Si）为主，内外层之间及膜与锌基体之间的化学成分呈梯度变化；和单独的钼酸盐膜、硅烷膜相比，2种复合膜对腐蚀的阴极过程的抑制明显增加，自腐蚀电流减小至单层膜的1/5以下，耐蚀性显著提高，接近常规铬酸盐钝化膜。

Structure and Corrosion Resistance of Molybdate/Silane Composite Film on Galvanized Steel

Hot-dip galvanized steel sheets were firstly immersed in a molybdate solution and then in a silane solution ( called two-step method) or directly dipped in a solution containing silane and molybdate as additive (called one-step method) to obtain molybdate/silane composite films on the zinc coating. The chemical composition of the films was determined by X-ray Photoelectron Spectroscopy (XPS) and Augur Electron Spectroscopy (AES). The corrosion resistance of these films was investigated by means of Tafel polarization curve measurement and neutral salt spray (NSS) test and compared with that of single molybdate film and silane film respectively. The results show that the molybdate/silane composite film obtained by one-step treatment exhibits the same double-layer structure as that by two-step treatment. The inner layer, similar to molybdate conversion film, mainly contain O、Mo、Zn、P , and the outer layer, similar to silane film, mainly contain C、O、Si. Moreover, the chemical compositions of composite films are changed gradually from substrate to film and from the inner layer to the outer layer. Compared with single molybdate film and silane film, the cathode polarization process of the composite films is inhibited evidently. The corrosion current is decreased to the less than 1/5 of that of the single films, while the corrosion resistance of composite films is enhanced remarkably, close to that of the conventional chromate passivation film.