Fabrication of dual anti-corrosive polyaniline microcapsules via Pickering emulsion for active corrosion protection of steel

Abstract

A novel kind of inhibitor-loaded polyaniline (PANI) microcapsule was prepared by Pickering emulsion photopolymerization using polyaniline particles as the Pickering emulsifier. In our strategy, water-dispersible polyaniline nanoparticles were firstly synthesized using a micelle template method and used to stabilize oil-in-water emulsions, in which the oil phase contained photo-crosslinkable and pH sensitive monomers and a photo-initiator. Under UV light, the pH-responsive monomers underwent photo-polymerization and crosslinking and converted to microcapsule shells. During this process, polyaniline nanoparticles were trapped in the microcapsule shells, leading to the formation of PANI microcapsules. The structure and morphology of the synthesized PANI microcapsules were analyzed using FTIR spectroscopy, SEM, and EDX mapping. The inhibitor (mercaptobenzothiazole, MBT) was subsequently incorporated into the PANI microcapsule as a functional core and demonstrated pH-sensitive releasing behavior. With the anti-corrosive PANI as the microcapsule wall and the inhibitor MBT as the core, the as-prepared MBT loaded PANI (MBT@PANI) microcapsule could afford dual corrosion protection, allowing smart protection of metals when exposed to corrosive conditions. The MBT@PANI microcapsules were embedded in UV-cured coating for protecting steel. The corrosion protection performance of the coating with MBT@PANI microcapsules was evaluated using the electrochemical impedance spectroscopy technique and salt spray test, which demonstrated the synergistic inhibition effect of the PANI wall and the loaded MBT in improving anti-corrosion performance of the coating.