Anti-corrosive and self-healing properties of epoxy coatings loaded with montmorillonite modified with zinc-based ionic liquid

Abstract

In this work, the outstanding corrosion resistance of coated steel and self-healing ability of epoxy coatings loaded with 1 % of sodium montmorillonite (MMT-Na+) clay modified with bis-(1-butyl-3-methylimidazolium) zinc tetrachloride (bmim2[ZnCl4]) was successfully demonstrated. The corrosion protection properties and self-healing ability of artificially scratched ER coatings containing 1 % of MMT-bmim2[ZnCl4] were compared with those loaded with MMT-Na+, MMT-ZnCl2 and the MMT modified with the ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl), using electrochemical impedance spectroscopy (EIS) under saline medium. The presence of 1 % clay modified with ZnCl2 and bmim2[ZnCl4] promoted outstanding anti-corrosion protection to the scratched ER coatings. The last one exhibited the best anti-corrosive response, whose |Z|f=0.01Hz value corresponded to 2.9 × 106 Ω·cm2 after 24 h immersion and increased by around two orders of magnitude after 360 h immersion in saline solution. Furthermore, the charge transfer resistance (Rct) increased after 360 h immersion followed by significant decrease in double-layer capacitance values (Cdl) at the electrolyte/metal interface. The self-healing ability was also confirmed by SEM/EDX (due to the presence of Zn in the scratched region) and by visual observation of the scratched region after immersion in the saline solution for 360 h.