Zn-Al合金镀层低铬钝化膜的组成和耐蚀性

目前，在中国采用热浸镀Zn及其合金一直是防止钢材在自然环境中腐蚀的最经济有效的方法，为了提高镀层的防腐和涂装性能，往往在其表面进行钝化处理。传统的镀锌层钝化处理工艺均采用高浓度的铬酸盐溶液， 这对环境污染和人体的危害较严重。随着环境保护问题日益引起人们的重视，在传统的高铬钝化基础上，低浓度铬酸盐钝化开始步入实用性阶段(吴双成，1996；卢燕平等，1995)。但是，目前低铬钝化研究主要集中于热浸镀Zn或电镀Zn镀层，而合金镀层由于化学稳定性高，与铬酸溶液自发反应能力差，无法采用常规的低铬钝化方法处理，有关这方面的报道目前尚少。王洪仁(1998)对Zn-Al合金镀层的低铬钝化处理进行了有益的探索，获得了一个优化的低铬钝化配方和稳定的钝化工艺，并成功地应用于热浸镀Zn-Al合金镀层的表面防锈处理；实验证明，海水在模拟浸泡6个月后，钝化处理Zn-Al合金镀层的腐蚀失重比未钝化样品降低65.9%，表明低铬酸盐钝化使Zn-Al合金镀层的耐海水腐蚀性能得到显著提高(Li Y et al.，2001)。本文作者在前人基础上对Zn-Al合金镀层低铬钝化膜的组成和耐盐雾腐蚀性进行了研究，并初步探讨了钝化膜的形成过程及其耐蚀机理。对Zn-Al合金镀层低铬钝化处理技术的研究，不仅大大降低了对环境的污染和人体的危害，也是在低铬钝化研究方面的重大突破，具有十分重要的意义和实际应用价值。

Composition and Anti-Corrosion Performance of Chromate Conversion Film on Hot Dip Zn-Al Alloy Coating

Low concentration chromate conversion technology was successively applied on ho t dip Zn-Al alloy coating. The primary dissolution of the active Zn-rich phase with in the coating immersed in the conversion solution associated with the evidence that the relative activities of each of the elements composing the A l-Zn coatings in the 0.5mo l /L H2 SO4 was Zn >A l > steel. XPS and AES analyses indicated that the chromate conversion film formed on the surface of the Zn-A l alloy coating consists of Cr(OH)3 , Cr2O3, ZnO, Al2O3 , and TiO2 . The results of CASS test confirmed that the corrosion resistance of Zn-Al alloy coating was improved remarkably after the chromate conversion treatment. The fingding that corrosion, especially local corrosion of Zn-Al alloy coating is remarkably reduced may be attributable to the fact that the chromate conversion film in prohibits the anodic and cathodic reactions of the corrosion process, and improves the surface state of the Zn-Al alloy coating.