Anticorrosion performance of the coating/metal system by electrochemical impedance spectra

In order to investigate the anticorrosion performance of the organic coating/metal system, electrochemical impedance spectra (EIS) were measured in the 3.5wt% NaCl solution, the chemical component and the formation of corrosion products scale were analyzed by laser Raman microspectroscopy, and the pattern of the organic coating/metal system was observed by scanning electron microscopy (SEM). The characteristics and the delamination process of the organic coating/metal system were investigated systematically, and the emphases were on the transportation of the corrosive medium and the changes of the coating/metal interface. The results show that the impedance decreases at the initial immersion, then increases at the middle-immersion, and again decreases at last, which is related to the corrosion products scale. The concentration of Cl⁻ in the coating, which destroys the corrosion products scale, increases with the immersion time.