Intelligent anti-corrosion coating with multiple protections using active nanocontainers of Zn[sbnd]Al LDH equipped with ZIF-8 encapsulated environment-friendly corrosion inhibitors

Abstract

The incalculable metal corrosion loss makes the research of long-term corrosion resistant coatings attract much attention. Herein, we demonstrated a new strategy for constructing a pH-responsive nanocontainer as a gatekeeper, which consisted of a laminated double hydroxide (LDH) surface in situ grown ZIF-8 containing the corrosion inhibitor of 2-mercaptobenzimidazole (MBM). The shell-core structures of the composite fillers displayed the excellent barrier performance and pH-responsive controlled release properties in epoxy (EP) coatings. Electrochemical impedance spectroscopy and salt spray tests were conducted to investigate the multifunctional role in providing an intelligent anti-corrosion MBM@ZIF-8@LDH/EP composite coating. After immersing in salt solution (3.5 wt%) for 30 days, the impedance value of the MBM@ZIF-8@LDH/EP coating at 0.01 Hz (|Z|0.01 Hz) was 2.82 × 108 Ω∙cm2, which was about four orders of magnitude higher than that of the epoxy coating (1.54 × 104 Ω∙cm2). The outstanding corrosion protection of MBM@ZIF-8@LDH was attributed to not only the compactness improvement of the composite coating, but also the anion exchange capability to act as a storage station for chloride ions. Meanwhile, the active filler could be used as a pH-responsive nanocontainer to release the loaded corrosion inhibitor of MBM and prevented further damage to the steel substrate, displaying a self-healing behavior. This strategy provides a new idea to combine perfect barrier effect and active anti-corrosion performance to prepare high-performance anti-corrosion and self-healing coatings. The multi-protective smart anti-corrosive coating would be a candidate with excellent performance for use in a variety of fields.