Anti-corrosion performance of aniline trimer-containing sol–gel hybrid coatings for mild steel substrate

Novel electroactive sol–gel hybrid coatings were synthesized by hydrolysis and condensation reaction of tetraethoxysilane (TEOS) and different mass ratios of silane-capped aniline trimer (TSUPQD) on the surface of Q235 steel. Microstructure, thermal stability, and corrosion resistance of as-prepared hybrid coatings were characterized by FTIR, UV–Vis, SEM, TGA, CA measurement, polarization curve, and electrochemical impedance spectroscopy. It could be seen that the i_corr value of as-prepared novel coating was markedly lower than those of pure TEOS-based coating and bare substrate. EIS results indicated that the impedance of hybrid coating was higher than that of Q235 steel substrate, indicating the effective protective property for substrate. Meanwhile, the aniline trimer-based hybrid coatings presented much higher impedance after immersion in 3.5 wt% NaCl for 200 h, and the best corrosion performance was acquired when the mass ratio of TEOS/TSUPQD is 100:4. The XRD and SEM analysis of the corrosion product beneath the hybrid coatings showed that the redox catalytic capability of aniline trimer could induce the Q235 substrate to form the passive films which mainly consisted of Fe₂O₃ and Fe₃O₄. [Figure not available: see fulltext.].