辅助成膜剂对锌酸盐镀锌蓝白钝化外观的影响

摘要

镀锌蓝白钝化膜的颜色相比彩色钝化单一,钝化膜的颜色更易受到金属离子的影响,辅助成膜剂可以提高镀锌钝化膜的致密性和耐蚀性,改变钝化膜的颜色.研究发现,在三价铬基础钝化液中添加适量的硫酸钴,能增加蓝白钝化膜的蓝色并延长硫酸铜点滴试验的变色时间,但对增强钝化膜的抗盐雾性能不明显;加入适量的氯化镍,能改善蓝白钝化膜的外观,但不显著;加入0.5～2.0 g/L的镧离子对蓝白钝化膜外观没有明显的改善作用.硅酸钠虽然能提高钝化膜的耐蚀性,但增大了钝化试样的杂色,使得钝化膜的颜色不均匀.%Auxiliary film-former can improve the compactness and corrosion resistance of passivation film and change the film color.Compared with blue-white passivation,the color of coloring passivation is single and more susceptible to the effects of metal ions.Results show that:adding suitable amount of cobalt sulfate to trivalent chromium based passivation solution can increase the blue color of blue-white passivation film and prolong the discoloration time of copper sulfate spot test,but no obvious effect in strengthening the salt spray resistance of the passivation film;adding suitable amount of nickel chloride can improve the appearance of the blue-white passivation film,but not obviously;adding 0.5 ～ 2 g/L of lanthanum ions has no significant improvement on the appearance of the blue passivation film.Although sodium silicate can improve the corrosion resistance of the passivation film,but mottled color will increased and makes the passivation film non uniform.