Evaluation of the anti-corrosion performance of poly(o-toluidine)/silica epoxy composite coatings

Addressing the dispersion and solubility issues of traditional polyaniline in organic coatings, we developed a poly(o-toluidine)/silica (PSC) composite in this work. Different from standard polyaniline, the methyl group in poly(o-toluidine) (POT) offers steric hindrance, which helps the material disperse better within the epoxy (EP) matrix. We synthesized the PSC composites using in-situ chemical oxidation and added them to EP coatings. Electrochemical tests show that the 3 wt% PSC-EP coating offers distinct corrosion resistance, achieving a protection efficiency of 98.56 % and a charge transfer resistance ( R _ct ) of 10,483 Ω·cm², which is more than three times that of pure EP. The corrosion current density dropped significantly to 7.07 × 10⁻⁷ A/cm². In terms of mechanism, the uniform PSC dispersion acts as a "labyrinth" to block corrosive ions, while the POT component helps form a stable passivation layer on the steel. These results suggest that silica-supported POT is a practical, high-performance alternative to conventional conductive polymer coatings.