Synthesis and characterization of a poly(o-anisidine)-SiC composite and its application for corrosion protection of steel

Conducting polymers have been widely used for corrosion protection of metals. Herein, a poly(o-anisidine) (POA)-SiC composite was synthesized by an in situ chemical oxidative polymerization method in a p-toluenesulfonic acid medium. The structure and morphology of the POA-SiC composite were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). The thermal stability was studied by thermal gravimetric analysis (TGA) and the electrochemical behavior was studied by cyclic voltammetry (CV) measurements. Subsequently, the synthesized POA-SiC composite was introduced to epoxy resin through a solution blending method, and the three-component POASiC/epoxy hybrid materials were applied onto the surface of steel. The corrosion resistance of the POASiC/epoxy coating was evaluated by Tafel polarization and electrochemical impedance spectroscopy measurements in a 3.5 wt% NaCl solution and also compared with that of a POA/epoxy coating. The results demonstrated that the POA-SiC composite containing coating has a higher corrosion resistance than that of POA, with a lower corrosion rate and a higher corrosion protection efficiency. The excellent corrosion protection ability of the POA-SiC/epoxy coating is mainly attributed to the micro/nano structure of the POA-SiC composite which promoted a good compatibility with the epoxy resin and thus decreased the pinhole defects of the coating, and a conclusion was drawn that the protection is associated with the barrier effect of SiC nanoparticles, and the passivation and hydrophobic effects of POA. Furthermore, the protection mechanisms of the POA/epoxy coating and the POA-SiC/epoxy coating were also discussed.