通过单因素对比实验,研究了硅酸钠浓度、添加剂以及封闭时间、封闭温度等对磷化膜封闭效果的影响,获得了最佳封闭工艺。采用加速腐蚀实验方法和电化学测试技术,将硅酸盐封闭的效果与铬酸盐封闭进行了对比,并探讨了封闭机理。结果表明:硅酸钠封闭后,磷化膜中性盐雾试验(NSS)24h未见腐蚀,自腐蚀电位正移,自腐蚀电流明显降低;硅酸钠封闭是通过形成硅酸盐沉淀封闭磷化膜的微小凹陷处,从而提高磷化膜耐蚀性的。

By single factor experiment, the best sealing prosess was obtained after studying the influence of the concentration of sodium silicate, the additives, sealing time and sealing temperature on the the sealing effect of phosphate coating. The sealing effect of silicate and chromate salt was compared by the accelerated corrosion experiment method and electrochemical test technology and the mechanism of sealing was explored. The results show that after sealing by sodium silicate, the phosphate coating has not seen the corrosion after 24 hours’neutral salt spray test and corrosion potential moves positively while the corrosion current reduces significantly; The sodium silicatesealing can improve the corrosion resistance of the phosphate coating because of the silicate deposite which can seal the hollow of the phosphate coating.