电镀锌及硅酸盐钝化工艺研究

【作者】 刘文君；

【导师】 张英杰；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2007， 硕士

【摘要】 本文研究了电镀锌和镀锌层硅酸盐无铬钝化工艺,主要研究内容包括以下几个方面:以电镀锌工艺体系作为研究对象,对各种体系的优缺点进行了对比,并选择氯化物钾盐镀锌。通过正交优化实验确定了氯化钾镀锌工艺的最佳工艺条件:ZnCl₂:80g/L:KCl:200g/L;H₃BO₃:35g/L;主光亮剂:2ml/L;载体光亮剂:10ml/L;辅助光亮剂:6ml/L;pH:5.0;电流密度:1～1.5A/dm²。确定了硅酸盐钝化工艺的最佳条件:Na₂SiO₃:20g/L;H₂SO₄:3g/L;H₂O₂:30g/L;添加剂:10ml/L;pH值:2.5;钝化时间:60s。研究了各工艺因素对氯化钾镀锌工艺中镀层外观质量的影响,试验结果表明:镀液中主光亮剂卞叉丙酮的含量过低则镀层黯淡无光,表面粗糙,不平滑,含量过高则试片高电流密度区易烧焦,析氢现象严重,边缘效应明显;载体光亮剂含量过低则卞叉丙酮无法溶解,镀层粗糙不平滑,含量过高则低电流密度区域发黑光亮范围缩小;辅助光亮剂含量过低则光亮范围小,低电流密度区域发黑,含量过高则边缘效应明显且镀层表面发黄;镀液PH值过低则析氢严重,pH值过高则镀层表面发雾,光亮性变差,镀液出现浑浊;镀层厚度随电镀时间的变长而变厚。研究了影响钝化膜耐蚀性的因素,结果表明,钝化时间、温度、pH值、钝化液各组分含量对钝化膜的耐蚀性影响很大,偏离了其最佳值钝化膜的耐蚀就会明显降低,其它工艺条件如老化时间、干燥方式对钝化膜耐蚀性也有较明显的影响,老化时间以24h最佳,干燥方式采用热风干燥。而空气中停留时间对耐蚀性影响很微弱,5s较好。将硅酸盐钝化工艺与其它各种无铬钝化工艺进行了对比试验,结果表明:硅酸盐钝化液具有良好的稳定性,硅酸盐钝化膜的耐腐蚀性明显好与其他无铬钝化膜,该工艺在代替镀锌铬酸盐钝化方面具有良好的应用前景。更多还原

【Abstract】 The technics of zinc-electroplating and the silicate non-chrome passivation of zinc-plating are studied in this paper.The research we have done including the follows:By the comparation of different systems,We get the appropriate method of zinc-electroplating in the solution that contains kalium.We also gain the optimal technics using the orthogonal experiments,that is,ZnCl_2:80g/L; KCl:200g/L;H₃BO₃:35g/L;main brightener:2ml;carrier brightener:2ml; supplementary brightener:2ml;pH:5.0;current density:1～1.5A/dm².and we get the best technics by orthogonal experiments as follows,Na₂SiO₃:20g/L; H₂SO₄:3g/L;H₂O₂:30g/L;additive:10g/L;pH:2.5;passivation time:60s.The technics factors have a distinct effect on the appearance of coatings, especially the additive content and pH effect directly the brightness,leveling and the stability of plating solution,the plating time has relation with the thickness of coatings.The experiments we have done shows that,when the main brightener acetune content is too low,the coatings will be dull and coarseness.However,when it becomes too high,the coatings will be burned in high-density area,and there will be serious hydrogen bubbing and edge effect. If the carrier brightener content is lower,main brightener acetune cann’t be dissolved and the coatings are coarse and tough.But when it becomes too high, the coatings in low-density area will be dark and lightness area becomes smaller.When supplementary brightener content is low,the coatings in low-density area will be dark.The edge effect is serious and the coatings become yellow in high-density area.If pH in solution is low,hydrogen bubbing is high,and when it becomes high,the coatings are dark and fogged, the solution is turbidity.The coatings thickness becomes larger with the plating time becoming longer.Some factors influencing the corrosion resistance of passivation film are presented in this paper,passivation time,temperature,pH,passivation solution content are the most important factors.In addition,there are other factors that can have important influence,such as aging time,drying method.The optimal aging time is 24h,and we can use heated air to dry.The dwell time in the air is not important,5s is better.The silicate non-chrome passivation solution is stable.We have studied the corrosion resistance in silicate passivation of the coatings and found silicate passivation films have better corrosion resistance than other non-chrome passivation films in NSS and dipping-in brine experiments.The technics has has good prospect in zinc-electroplating passivation for replacing chromate.更多还原