硅烷膜的阴极电化学辅助沉积及其防护性能

CATHODICALLY ELECTROCHEMICAL-ASSISTED DEPOSITION AND PROTECTIVE PROPERTIES OF SILANE FILMS

采用电化学辅助技术在LY12铝合金表面沉积了两种防护性硅烷膜(1,2-二-(三乙氧基硅基)乙烷(BTSE)膜与十二烷基三甲氧基硅烷(DTMS)膜)．电化学阻抗谱测试结果显示,经硅烷化处理后铝合金的耐蚀性能得到大幅度提高,并且发现在阴极电位下沉积所得硅烷膜的耐蚀性能较常规“浸涂法”有明显提高;两种硅烷膜均存在一个最佳的“临界阴极电位”(-0．8 V),在此电位下制得的膜耐蚀性最佳．扫描电镜观察显示临界电位下所得硅烷膜最为完整致密,电位过正不利于成膜,而电位继续变负膜表面呈现多孔形貌,可能与氢气的生成并溢出破坏表面有关．由于在硅烷分子中含有疏水性较强的十二烷基长链,DTMS 膜具有更好的耐蚀性．

Two types of protective silane films, bis-1, 2-[triethoxysilyl] ethane （BTSE） and dodecyltrimethoxysilane （DTMS）, were deposited on LY12 aluminum alloys with aiding of electrochemical technique. Electrochemical impedance spectroscopy （EIS） tests show that after silanization the corrosion resistances of Al alloys are increased significantly, especially after deposition at cathodic potentials. A critical deposition potential （CDP）, namely -0.8 V, is generally found for each silane system, at which the highest protectiveness is obtained. Scanning electron microscopy （SEM） shows that silane films prepared at CDP display the highest uniformity and density. Applying more positive potentials does not facilitate the film formation. On the other hand, when potential shifts more negative the surface of films presents porous morphology, probably due to the intensive evolving of hydrogen bubbling near the surface. Due to the presence of long hydrophobic Dodecyl chain in bone structure, DTMS films display the best barrier properties.