Fabrication of Poly(o/m-Toluidine)–SiC/Zinc Bilayer Coatings and Evaluation of Their Corrosion Resistances

摘要

The purpose of this research was to study the structure and corrosion resistance of poly(o/m-toluidine)-SiC/zinc (Zn) bilayer coatings. Poly(o/m-toluidine) films, such as poly(o-toluidine) (POT) and poly(m-toluidine) (PMT), were chemically deposited on the surface of composite SiC/Zn coating using the solution evaporation method. The structures of poly(o/m-toluidine) were characterized by various optic techniques and the electrochemical behavior was studied by cyclic voltammetry (CV). The structures and morphologies of the SiC/Zn coating were detected by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and scanning electron microscopy (SEM). Thereafter, the corrosion resistances of electrodeposited and bilayer coatings were investigated in 3.5% NaCl solution by electrochemical corrosion techniques and an accelerated immersion test. The results showed that the outer POT film exhibits a lower corrosion behavior with respect to PMT, which significantly reduces the corrosion rate of SiC/Zn coating and prolongs the service life of the zinc matrix. The conclusion demontrates that the stronger adsorptive POT film ensures the formed POT–SiC/Zn bilayer coatings possess a compact and low-defect surface, which facilitates POT film to develop its excellent barrier and passivation properties against corrosion.