借助优化钛/锆基化学转化工艺,在碱性无氰镀锌层基体上获得了环保型的无铬转化膜,并与铬酸盐彩色钝化膜作对比.中性盐雾试验、动电位极化和电化学阻抗谱测试结果表明:钛/锆基化学转化膜出现白锈时间为96 h,达到铬酸盐彩色钝化膜标准,且呈现出较低的腐蚀电流和较高的极化电阻,但钝化特性不如铬酸盐彩色钝化膜明显.
In this paper,we obtained environmental-friendly chromium-free chemical conversion coating on the non-cyanide alkaline zinc electroplating layer by employing the optimized Ti/Zr based conversion technique.At the same time,the performances of the Ti/Zr based conversion coating were compared with chromate colour passivation coating.The corrosion resistances of the conversion coatings were investigated by using neutral salt spray(NSS) test,potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The results showed that the white rust appeared after 96 hours when the NSS test was performed on the Ti/Zr based conversion coating,which was close to the corrosion resistance rating of chromate colour passivation coating.Compared with the chromate passivation coating,the Ti/Zr based conversion coating showed lower corrosion current and higher polarization resistance.However,the passivation characteristic of the former was less evident than the latter.
[1]Perfetti B M.A comparison of pretreatments for pre-painted galvanized sheets[J].Metal Finishing,1983,81(5):57-59.
[2]Xiaoge Gregory Zhang(章小鸽).Corrosion and electro-chemistry of zinc[M].Beijing:China Metallurgical In-dustry Press,2008:19-22.
[3]John W Bibber.Chromium-free conversion coatings forzinc and its alloys[J].Journal of Applied Surface Fin-ishing,2007,2(4):273-275.
[4]An Chengqiang(安成强),Hao Jianjun(郝建军),MuShihui(牟世辉).Advances in nonchromium passiva-tion of galvanized steel plate[J].Surface Technology(表面技术),2003,32(2):6-8.
[5]Motoaki Hara,Ryoichi Ichino,Masazumi Okido,et al.Corrosion protection property of colloidal silicate filmon galvanized steel[J].Surface and Coatings Technolo-gy,2003,(169/170):679-681.
[6]Zhang Jianghong(章江洪),Zhang Yingjie(张英杰),Yan Lei(闫磊),et al.Progress in research on chromi-um-free passivation of galvanized wares[J].MaterialsProtection(材料保护),2009,42(3):48-53.
[7]Smit M A,Sykes J M.Titanium based conversion coat-ings on aluminium alloy[J].Surface Engineering,1999,15(5):407-410.
[8]Lunder O,Simensen C,Yu Y,et al.Formation and char-acterisation of Ti-Zr based conversion layers onAA6060 aluminium[J].Surface and Coatings Technol-ogy,2004,184(2/3):278-290.
[9]Shen Pinhua(沈品华),Tu Zhenmi(屠振密).Zinc andzinc alloies electroplating[M].Beijing:China MachinePress,2001:119-127.
[10]Verdiera S,Nvan der Laak,Dalard F,et al.An electro-chemical and SEM study of the mechanism of forma-tion,morphology,and composition of titanium or zirco-nium fluoride-based coatings[J].Surface and CoatingsTechnology,2006,200:2955-2964.
[11]Hamlaoui Y,Pedraza F,Tifouti L.Corrosion monitoringof galvanised coatings through electrochemical imped-ance spectroscopy[J].Corrosion Science,2008,50:1558-1566.
[12]Cachet C,Ganne F,Maurin G,et al.EIS investigationof zinc dissolution in aerated sulfate medium.Part I:Bulk zinc[J].Electrochimica Acta,2001,47(3):509.
