Grafting of polyaniline onto polydopamine-wrapped carbon nanotubes to enhance corrosion protection properties of epoxy coating

Ordinary coatings can hardly meet the long-term corrosion protection requirements of modern industries. Incorporating high-performance fillers in these coatings is considered an effective way to solve this problem. In this work, the carbon nanotubes (CNTs) with polydopamine (PDA) modification was obtained by self-polymerization of dopamine on the surface of carbon nanotubes (CNTs), and then polyaniline (PANI) was grafted onto the surface of CNTs-PDA, and CNTs-PDA-PANI nanocomposites were successfully prepared. This novel strategy improves the dispersion of CNTs while increasing their surface active sites, which facilitates the uniform grafting of PANI onto the CNTs surface. Finally, the obtained nanocomposites were incorporated into epoxy resins (EP) to study their enhancement of epoxy coatings under both passive and active corrosion protection mechanisms. Electrochemical impedance spectroscopy (EIS) showed that the low-frequency impedance of CNTs-PDA-PANI/EP coating was still as high as 1.19 × 1010 Ωcm2 after 50 days of immersion in 3.5 wt% NaCl solution, which was about two orders of magnitude higher than that of the pure epoxy coating. The superior corrosion protection mechanism was attributed to the barrier of the nanofillers to the corrosive medium and the induction of the metal passivation film. Therefore, this nanocomposite construction strategy may have a high potential in the field of corrosion protection.