Preparation of Poly(o-ethylaniline)-SiC/Zinc Bilayer Coatings and Study of Its Corrosion Resistance Properties

Abstract

The present work aims to study the differences of structure and corrosion resistance of poly(o-ethylaniline) (POE)-SiC/zinc (Zn) and POE/SiC-Zn bilayer coatings. Herein, POE and POE/SiC composite (PSC) were prepared by emulsion polymerization method, Zinc (Zn) and SiC/Zn composite coatings were prepared by electrodeposited technique. The structures of polymer materials were characterized by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), and the electrochemical behavior was studied by cyclic voltammetry (CV) measurement. Subsequently, the polymer materials were spread on the surface of electrodeposited coatings and thus obtained POE-Zn, PSC-Zn and POE-SiC/Zn bilayer coatings. The structures of Zn and SiC/Zn coatings were characterized by FTIR, XRD and energy dispersion spectroscopy (EDS) and the surface morphologies of all coatings were also studied by SEM. The corrosion resistances of the coatings were investigated in 3.5% NaCl solution by Tafel polarization curve and electrochemical impedance spectroscopy (EIS). It was shown that the addition of SiC nanoparticles to Zn matrix significantly changed the microstructure and improved the corrosion resistance. POE-SiC/Zn coating is more protective than PSC-Zn and POE-Zn coatings, with a corrosion rate of 0.021 mm/year and the corrosion protection efficiency up to 98.86%. The excellent corrosion protection of POE-SiC/Zn bilayer coatings was attributed to the fact that inner SiC/Zn coating possess a compact micro/nano surface, which facilitates the good embedding of outer POE coating and thereby eliminates the damage of the residual air in the grooves to outer coating. A conclusion was depicted that the protection is associated with the double barrier effects of outer/inner coatings and the passivation effect of POE. The protection mechanism conferred by POE-SiC/Zn bilayer coatings was also discussed.