Ion-triggered calcium hydroxide microcapsules for enhanced corrosion resistance of steel bars

Abstract

Herein, we synthesized Ca(OH)₂ microcapsules with ion-responsive shells composed of cross-linked poly-ionic liquids (CPILs). By exchanging PF₆⁻ with Cl⁻ in water, the hydrophobic poly-ionic liquids (PILs) on the shell are converted to hydrophilic channels. The encapsulated Ca(OH)₂ can permeate through the hydrophilic channels and release OH⁻. Meanwhile, the Cl⁻ content can be reduced. The release rate of Ca(OH)₂ is influenced by the content of monomers and concentration of Cl⁻ ions in water. SO₄²⁻ can also trigger the release of Ca(OH)₂ from the microcapsule. With these microcapsules, Q235 steel exhibited promising corrosion resistance in simulated seawater. These results indicate that encapsulation of corrosion inhibitors is highly desirable for enhanced corrosion resistance of steel bars and the proposed approach can be used to encapsulate various corrosion inhibitors and functional materials for a wide range of applications.