新型双季铵盐缓蚀剂的合成与性能评价

Synthesis and Property Evaluation of New Double Quaternary Ammonium Salt as Corrosion Inhibitor

以乌洛托品和二卤代烃为原料经季铵化反应合成了4种乌洛托品双季铵盐缓蚀剂:溴化1,2-二乌洛托品乙烷、溴化1,4-二乌洛托品丁烷、溴化1,6-二乌洛托品己烷、溴化1,8-二乌洛托品辛烷。采用失重法、电化学方法研究了双季铵盐缓蚀剂在15%(质量分数)HCl溶液中对QT-800钢的缓蚀性能,并采用量子化学计算对缓蚀剂的缓蚀机理进行了分析,通过电子扫描显微镜对QT-800钢的腐蚀表面进行分析。结果表明:双季铵盐缓蚀剂的缓蚀性能随缓蚀剂分子碳链长度的增加而提高,其中溴化1,8-二乌洛托品辛烷具有最好的缓蚀效果,其加量在0.7%~1.0%(质量分数)时,腐蚀速率低于4g/(m^2·h);溴化1,8-二乌洛托品辛烷属于能同时抑制阳极反应与阴极反应的混合型缓蚀剂;缓蚀剂分子的能隙以及它们在铁表面的吸附能均随着缓蚀剂碳链长度的增加而增大,且吸附能远大于水分子吸附能,缓蚀剂分子能够吸附在QT-800钢表面,抑制点蚀的发生。

Four kinds of double quaternary ammonium salt corrosion inhibitors-1,2-diullotropine ethane bromide,1,4-diullotropine butane bromide,1,6-diullotropine hexane bromide,1,8-diullotropine octane bromide-were synthesized using urotropine and dihalogenated hydrocarbon as raw materials by quaternary ammonium reaction.The corrosion inhibition performance of double quaternary ammonium salt corrosion inhibitors to QT-800 steel in 15%(mass fraction)HCl was studied by weight-loss method and electrochemical method,the mechanism of corrosion inhibitors was analyzed by quantum chemical calculation,and the surface after corrosion was analyzed by electron scanning microscopy.The results show that the corrosion inhibition performance of double quaternary ammonium salts increased with the increase of carbon chain length of corrosion inhibitor molecule.1,8-diullotropine octane bromide showed the best corrosion inhibition among four corrosion inhibitors,which had a corrosion rate lower than4 g/(m^2·h)when its dosage was in the range of 0.7%-1.0%(mass fraction).1,8-diullotropine octane bromide was a mixed inhibitor that inhibits both anodic reaction and cathodic reaction.The energy gaps of the corrosion inhibitor molecules and their adsorption energy on the surface of iron increased with the increase of carbon chain length of corrosion inhibitor,and the adsorption energy was much greater than that of water molecule.So the corrosion inhibitor molecules could adsorb on the surface of QT-800 steel and inhibited pitting corrosion.