摘要
热镀锌重铬酸盐钝化毒性大、不环保。为解决此问题,研究了以无毒、无污染的铈盐取代剧毒重铬酸盐的钝化工艺,采用正交试验确定了热镀锌钢表面稀土转化膜的最佳成膜工艺参数,讨论了处理液组成、pH值、成膜温度及成膜时间等因素对稀土转化膜耐蚀性的影响,并采用中性盐雾试验(NSS)和极化曲线测定等方法评价了转化膜对热镀锌层的防护作用。结果表明,本工艺可以明显推迟热镀锌层出现白锈的时间;稀土转化膜同时抑制了热镀锌层腐蚀的阳极和阴极过程,腐蚀电流密度下降,极化电阻升高,显著改善了热镀锌层的耐蚀能力。
A nontoxic passivation process for galvanized steel,based on cerium salt solution as a replacement of highly toxic dichromate,was investigated.Thus orthogonal tests were carried out to determine the optimized parameters for the preparation of the rare earth chemical conversion film on the steel surface.The effects of bath composition,pH value,temperature and passivation time on the properties of the conversion film were discussed.Moreover,the protection of the galvanized steel by the conversion film was explored using neutral salt-spray test and polarization curve test as well.As the results,the optimum bath composition for the preparation of rare earth conversion film on galvanized steel was suggested as 20 g/L Ce(NO3)3·6H2O,30 mL/L H2O2,and 1.5 g/L H3BO3,and the optimized pH value,temperature,and duration were determined as 4,40 ℃,and 30 min.The rare earth conversion film could prevent the galvanized steel sheets from white rusting and simultaneously restrain cathodic and anodic reactions in corrosion process.At the same time,the rare earth conversion film was capable of decreasing the corrosion current density,increasing the polarization resistance,and significantly increasing the corrosion resistance of the galvanized steel.
出处
《材料保护》
CAS
CSCD
北大核心
2008年第8期28-31,79,共4页
Materials Protection
关键词
稀土转化膜
热浸镀锌
钝化
耐蚀性
正交试验
rare earth conversion film
hot-dip galvanizing
passivation
corrosion resistance
orthogondal test
