无机为主无铬复合钝化的综合对比研究与展望

基于镀锌层表面无铬钝化技术,从钝化膜性质、钝化液稳定性和成膜耐蚀机理3大方面,总结了以硅酸盐、钼酸盐、钛盐以及稀土金属盐为主要成膜物质的4种复合钝化体系的优缺点,认为耐蚀性最优的体系为硅酸盐体系;对比了各体系钝化液稳定性的差异及不同影响因素,总结了不同体系的相应改善方法,认为硅酸盐体系稳定性最好。阐明了硅酸盐、钼酸盐和钛盐体系通过不同复配方法可得到丰富多彩的颜色。钼酸盐、钛盐和稀土金属盐体系耐蚀机理类似,钝化液环境导致Zn;反应生成沉淀物附着于基体表面,而硅酸根的配位作用易形成网状大分子物质,达到均匀附着的效果。列举了各体系的最佳配伍原则。经过以上综合对比得到硅酸盐体系作为主要成膜物质应用前景较好,其膜层耐蚀性优良、膜层颜色多样、表面缺陷最少,而钼离子、稀土金属离子可作为添加剂提高膜层的自修复性能。

Comprehensive Comparative Study and Prospect of Inorganic-Based Chromium-Free Composite Passivation

Based on the chromium-free passivation technology on the surface of the galvanized layer, the advantages and disadvantages of four composite passivation systems with silicate, molybdate, titanium salt and rare earth metal salt as the main film-forming substances were summarized from the 3 aspects including the properties of the passivation film, the stability of the passivation solution and the corrosion resistance mechanism of the film, which showed that the system with the best corrosion resistance was the silicate system. The differences in the stability of the passivation solution of each system and the different influencing factors were compared, and the corresponding improvement methods of different systems were summarized, which indicated that the silicate system had the best stability. Besides, it was described that silicate, molybdate and titanium salt systems could obtain plenty of colors through different compounding methods. The corrosion resistance mechanisms of molybdate, titanium salt and rare earth metal salt systems were similar. The passivation solution environment caused Zn;reaction to produce precipitates that adhered to the surface of the substrate, while the complexation of silicate was obviously easy to form a network of macromolecular substances to achieve uniform adhesion. The best compatibility principles of each system were listed. Finally, through the above comprehensive comparison, it was found that the silicate system had a good application prospect as the main film-forming substance. Its film had excellent corrosion resistance, diverse film colors and minimal surface defects. Molybdenum ions and rare earth metal ions could be used as additives to improve self-repairing performance of film.