离子选择性涂层下碳钢表面腐蚀产物的XPS分析

CORROSION COMPOSITIONS OF CARBON STEEL UNDER ION-SELECTIVE COATINGS BY XPS

用XPS分析不同离子选择性涂层下碳钢表层的化学组成 .结果表明 ,SO2 - 4 型阴离子选择性和Na+ 型阳离子选择性涂层下碳钢表面锈层的主要成分是含结合水的Fe(OH) 2 和少量FeO ,SO2 - 4 型阴离子选择性 /Na+ 型阳离子选择性双极涂层下碳钢表面的主要成分是Fe0 ,Fe2 + 所占比例很少 .在涂装阴离子选择性涂层的碳钢表面可以检测到比较明显的Cl- 的XPS信号 ,而在涂装阳离子选择性涂层和双极性涂层的碳钢表面则不明显 .

Ion-selective (anion-selective,cation-selective and bipolar) phenolic coatings were prepared by mixing phenolic varnish with ion exchangers.SO 2- 4-type anion exchanger resin and Na +-type cation exchanger resin were utilized as anion and cation exchangers respectively.The bipolar coating consisted of an anion-selective inner layer and a cation-selective outer layer.The corrosion compositions of carbon steel depriving of the painted ion-selective coatings after exposure in 3%NaCl solution for 30 days were investigated by XPS.The research results of XPS showed that the main compositions in the surface layer of carbon steel are Fe 2+ ,OH -,O 2- and Cl -under SO 2- 4-type anion-selective coating,whereas the main compositions are Fe 2+ ,Fe 0,OH -,and O 2- under Na +-type cation-selective and SO 2- 4-type anion-selective / Na +-type cation-selective bipolar coatings.The XPS signal of Cl -can be inspected obviously on the surface layer of carbon steel with anion-selective coating,whereas there is no obvious signal in the case of cation-selective and bipolar coatings.This indicated that Cl - could migrate from the NaCl solution to the substrate metal when carbon steel covered with anion-selective coating,whereas the migration of Cl - would be blocked in the case of cation-selective and bipolar coatings.From these results,it can be concluded that SO 2- 4-type anion-selective coating has poor corrosion resistance,Na +-type cation-selective coating has better corrosion resistance,and SO 2- 4-type anion-selective/Na +-type cation-selective bipolar coating has excellent corrosion resistance.