Enhanced hydrophobicity and barrier property of anticorrosive coatings with silicified polyaniline filler

Polyaniline has excellent potential in metal surface protection due to oxidation-reduction reversibility. However, the poor dispersity and endurance of polyaniline limit its further application. Herein, trimethylsilyl-substituted polyaniline (PSiAn) was synthesized and characterized by FTIR and SEM-EDS. Results showed that silanes were successfully linked onto the PANI chains. The fabricated filler exhibits high hydrophobicity and good compatibility in the epoxy matrix. Incorporating PSiAn into epoxy coating has a significant influence to the barrier property, effectively reducing the porosity of coating and interrupting the permeation pathway of aggressive substance. The results of electrochemical impedance spectroscopy showed that the |Z|0.01 Hz of PSiAn/epoxy composite coatings still reached 1010 Ω cm2 after 60-day immersion in 3.5 wt% NaCl solution, which was almost three orders higher than that of the pristine coating. XPS and EIS confirmed the formation of dense complex on alloy surface. It turned out that the synergy between impermeability and passivation effect endowed epoxy coating with excellent corrosion resistance. The long-term effectiveness of anti-corrosion epoxy coating was significantly improved, and a novel approach to preparing a highly hydrophobic filler was proposed.