ULTRA-ALKALINE CORROSION RESISTANCE COATINGS VIA ELECTROPHORETIC SOL-GEL PROCESSING

传统的溶胶-凝胶工艺是在基材浸出到溶胶溶液中后进行热处理以形成致密的复合膜，而新的溶胶-凝胶工艺在室温下结合紫外线（UV）照射来提高铝的耐碱性腐蚀能力。环境温度下紫外辐照制备的溶胶-凝胶膜的抗碱性腐蚀性能是传统复合膜的2.4 ~ 2.6倍，加热温度为573K。耐碱性腐蚀性能的提高是涂层致密化的主要原因，这是由于消除了光激发引起的残留有机物。辐照膜的高耐碱性可能是由于形成了致密的涂层，以及在NaOH溶液渗透路径中反应物的重复制备和溶解引起的自修复作用。其次，研究了溶胶-凝胶电泳沉积法制备厚涂层的方法。镀层厚度随外加电压和时间的增加而增加。所得到的涂层比浸涂法得到的涂层更厚、密度更大。

Instead of conventional sol-gel process in which the heat treatment is performed for forming dense composite film after the dipping-withdrawing of substrate into the sol solution, a new sol-gel process incorporated with an ultraviolet(UV) -irradiation at an ambient temperature have been attempted to improve the alkaline corrosion resistance of aluminum. The sol-gel film prepared by UV -irradiation at an ambient temperature indicated the alkaline corrosion resistance superior in the range of 2.4 times to 2.6 times to that of the conventional composite film heated at 573K.The improvement of alkaline corrosion resistance was responsible for the densification of coating layer due to the elimination of residual organics induced by photo-exixitation. The high alkaline corrosion resistance of the irradiated film may be attributed to the formation of dense coating layer and the self repairing action caused by a repetition for preparation and dissolution of the reactant in the penetrating path of NaOH solution into the composite film. Next, the preparation of thick coating film by the sol-gel electrophoretic deposition method have been investigated. The thickness of coating layer was observed to increased with increasing applied voltage and time. The coating layer produced were thicker and more dense than those obtained in dip-coating.