Synthesis of inhibitor-loaded polyaniline microcapsules with dual anti-corrosion functions for protection of carbon steel

In this work, a novel type of two-shell structured inhibitor-loaded polyaniline (PANI) microcapsule was fabricated for efficient corrosion protection of carbon steel. In our strategy, modified SiO 2 nanoparticles were used to stabilize an oil phase containing aniline, photo-crosslinkable monomer and crosslinker. Upon UV irradiation, the monomer and crosslinker underwent polymerization and converted into the first shell of microcapsules, which endows sufficient stability and robustness to the microcapsules. The subsequent polymerization of aniline at the oil/water interface contributed to the second layer of the microcapsules shell, which functioned as anticorrosion filler and pH-sensitive gatekeeper of the microcapsules to realize the responsive release of the incorporated inhibitor simultaneously. Corrosion inhibitor (2-mercaptobenzothiazole, MBT) was encapsulated into the prepared polyaniline microcapsules and pH-responsive release of MBT from the microcapsule was demonstrated. The anti-corrosion performance of the epoxy embedded with MBT loaded polyaniline microcapsules was achieved by the combination of the passivation of the steel surface by PANI and the on-demand release of MBT during the corrosion process, thus affording dual corrosion protection for the mild steel. The results showed that MBT loaded polyaniline microcapsules exhibited significantly enhanced corrosion protection of carbon steel than unloaded polyaniline microcapsules as well as MBT, demonstrating a synergistic inhibition effect of MBT and PANI.