Preparation and investigation of the protective properties of bipolar coatings

Different ion-selective coatings were prepared. Electrochemical impedance spectroscopy was used to investigate the failure behaviour of the coatings immersed in 5 wt.% KCl solution at 60 °C. The corrosion product was analysed by scanning electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectroscopy. Results show that the products were mainly ferrous oxide for bipolar and anionic coatings. Some KCl and K elements were observed in varnish and cationic coating, in addition to ferrous oxide. The results indicate that bipolar and anionic coatings can inhibit ion permeation because of ionic selectivity and increasing of the cross-link density of the coatings facilitated by silane coupling agent KH550.