热镀铝锌层镧掺杂硅烷钝化膜的腐蚀性能

Study on Corrodibility of Hot Dip Al-Zn Layer Passivated with La(NO_3)_3-Doped BTESPT Solutions

采用掺杂硝酸镧的硅烷(BTESPT)钝化液处理热镀铝锌层:室温(25℃)浸渍,120℃固化30min,在铝锌层上形成镧盐掺杂硅烷钝化膜.研究了热镀铝锌基体钝化后的结构、表面形貌与腐蚀性能.傅立叶变换红外光谱(FTIR)表明,掺杂硝酸镧的硅烷溶液与铝锌基体表面发生了化学键合作用,形成SiOAl与SiOZn网络结构的钝化膜,钝化膜中主要的有机基团种类与无掺杂剂硅烷膜无显著差别.SEM/EDS研究结果表明:掺杂硝酸镧的硅烷膜均匀、致密、无明显微裂纹,硅烷膜中主要含有C,O,Si,S,Al,Zn,La等元素.耐蚀性研究表明,掺杂硝酸镧的硅烷钝化能明显降低腐蚀电位和腐蚀电流密度,增大极化电阻,使其耐蚀性远远高于无掺杂剂的硅烷钝化.

The hot dip Al-Zn layer was passivated with La（NO3）3-doped BTESPT solution in which the layer was dipped at 25 ℃and cured at 120 ℃for 30 min, thus forming a passive film on the layer. The structure, surface morphology and corrodibility of the substrate after passivation were studied experimentally. FTIR （Fourier transformation infra-red spectroscopy） showed that the La（NO3 ）3-doped BTESPT films have been successfully deposited by chemical bonding between the solution and hot dip A1-Zn substrate and by the formation of Si -- O -- Al and Si -- O -- Zn. No obvious difference is found between the components of major organic groups in the passive films deposited and the undoped BTESPT films. SEM results indicated that the films deposited are compact and homogeneous without clear tiny cracks. The EDS （energy dispersive spectrometry） results showed that the films consist mainly of such elements as C, O, Si, S,Al,Zn and La. The test results of corrosion resistance showed that the corrosion potential and current density of the passive films decrease obviously, while the polarization resistance increases. It is therefore proved that the passivisity by La（NO3）3-doped BTESPT is much higher than that without doping in regard to corrosion resistance.