Abstract:
A novel type of microcapsule with pH-responsive release and anti-corrosion function was prepared via the UV-initiated polymerization and interfacial polymerization of Pickering emulsion. Then the microcapsule was loaded with corrosion inhibitor 2-mercaptobenzothiazole (MBT) and embedded into epoxy coating for enhancing the anti-corrosion performance of coating. SiO
2 nanoparticles were used as the Pickering emulsifier to stabilize the oil phase of emulsion, which contained aniline, glycidyl methacrylate (GMA) and 1,6-hexanediol diacrylate (HDDA). GMA and HDDA underwent crosslinking along with the interior of the emulsion droplets and formed the first shell of microcapsule initiated by UV light. The polyaniline (PANI) was synthesized subsequently via chemical oxidative polymerization of aniline initiated by ammonium persulfate (APS) and acted as the second functional layer of microcapsule shell material. The shell of the as-prepared PGMA@PANI microcapsule is thus of composite structure. The PGMA shell stabilized the morphology of the emulsion droplets and improved the robustness of the microcapsule. The PANI shell functioned as anti-corrosion filler and a pH-sensitive gatekeeper to realize the responsive release of corrosion inhibitor. After being loaded MBT, the MBT-PGMA@PANI microcapsule could achieve dual anti-corrosion function. PANI could passivate the steel and released MBT could form dense barrier layer on the steel surface to resist corrosive medium. Electrochemical impedance spectroscopy (EIS) was used to test the performance of coating. The Bode plots showed that the impedance values at low frequency (|
Z|
f=0.1 Hz) of coating with 1% mass fracion of MBT-PGMA@PANI microcapsule could be maintain above 10
8 Ω·cm
2 after immersed in NaCl solution (
w=3.5%) for 30 d, demonstrating significant improvement of anti-corrosion performance.