Synergistic effect of homogeneously dispersed PANI-TiN nanocomposites towards long-term anticorrosive performance of epoxy coatings

Novel polyaniline-titanium nitride (PANI-TiN) nanocomposites were synthesized by one step chemical oxidation polymerization at a low temperature and PANI-TiN/epoxy coatings with enhanced corrosion resistance were obtained based on the synergistic effect of TiN nanoparticles and PANI nanorods. PANI-TiN nanocomposites and resultant epoxy coatings were characterized by Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Raman and X-ray photoelectron spectroscopy (XPS). Their anticorrosion performance in a 3.5 wt.% NaCl aqueous solution was investigated by the electrochemical impedance spectroscopy (EIS) and polarization curves. The results indicated that the corrosion resistance of PANI/epoxy coatings can be highly enhanced by introducing TiN nanoparticles to the PANI nanorods and the PANI-TiN/epoxy composite coating with 0.4 wt.% TiN (mass ratio to epoxy) exhibited the best corrosion protective performance, whose corrosion potential ( E corr = −0.338 V) was positively shifted by 0.235 V compared with pure epoxy matrix ( E corr = −0.573 V), and the corrosion current density was reduced by two orders of magnitude. The chemical structure of the rust layer and the anticorrosion mechanism were studied via X-ray diffraction analysis (XRD) and XPS. TiN nanoparticles showed a remarkably inhibiting effect on the agglomeration of PANI nanorods in epoxy coating. The corrosion resistance was attributed to the mixed mechanism of “passivation effect” of highly dispersed PANI and “labyrinth effect” of TiN nanoparticles.