硝酸铈处理对磷化膜组织和耐蚀性的影响

Effect of Cerium Nitrate Treatment on Morphology and Corrosion Resistance of Phosphate Conversion Coatings

为了发挥磷化膜和铈盐膜的优势,采用硝酸铈前处理或硝酸铈后处理对热镀锌层上的磷化膜进行改进,通过SEM,EDS,NSS和Tafel极化研究了硝酸铈改进磷化膜的显微组织和耐蚀性,并与铬酸盐钝化膜进行了比较。结果表明:硝酸铈前处理或后处理改进磷化膜均为含P,O,Ce和Zn化合物的复合膜,基本上克服了单一膜层的缺陷,使得复合膜的耐蚀性明显增强;硝酸铈后处理改进复合膜的耐蚀性优于铬酸盐钝化膜,有望成为高毒性铬酸盐钝化膜的替代品。

To fully exert the advantages of phosphate coatings and cerium salt coatings,the traditional phosphate conversion coatings on hot-dip galvanized steel were modified by cerium nitrate pretreatment or cerium nitrate post-sealing.The morphology and corrosion resistance of cerium nitrate modified phosphated coatings were investigated using scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）,neutral salt spray（NSS） test and Tafel polarization measurement,and was compared with that of chromate passivation coatings.The results show that phosphate coatings modified by cerium nitrate pretreatment or post-sealing are the composite coatings contained P,O,Zn and Ce and the disadvantages of the single coatings are overcome,thus the corrosion resistance of two comosite coatings is enhanced greatly.The corrosion resistance of the composite coatings modifed by cerium nitrate post-sealing is superior to that of chromate coatings,and it is the promising replacer of toxic chromate passivation coatings.