교류임피던스(EIS)법을 이용한 아연분말 및 편상아연 코팅의 방식성능 연구

Abstract

Corrosion is the disintegration of a metal into its constituent atoms, generally, due to the electrochemical oxidation of metal in reaction with oxygen in its environment. A well-know example of electrochemical oxidation is the formation of iron oxide on the iron surface, causing the degradation of its physical properties such as mechanical strength. Leaking containers, tanks, and pipelines often result in significant economic losses. Coating is the most economical, among the widely used methods to prevent corrosion. Zinc-rich coating is employed to protect steel from corrosion most effectively. However, the optimization to attain maximum anti-corrosion performance with minimum thickness of zinc-rich coating is always an engineering issue. In our group, the mixing of zinc flakes and spherical zinc for zinc-rich coating was investigated to enhance the barrier effect possibly by more efficient particle stacking. In this study, the anti-corrosion performance of spherical zinc particles and zinc flakes was systematically investigated. To consider the inter-dependency of operating parameters, the anti-corrosion performance was analyzed at different conditions of particle shape (sphere and flake), particle size (4~6μm, 6~9μm, 12~14μm, and 16~20μm), and pigment volume concentration (PVC) (30%, 50%, and 70%). Cross-sections of coatings were compared using SEM micrographs and electrochemical properties were measured by electrochemical impedance spectroscopy (EIS) as the major analysis tool. A couple of supplementary tests such as coating adhesion test and salt dipping test of 720 hours were employed to evaluate the anti-corrosion performance of coated samples. As a summary, zinc flake showed better anti-corrosion performance than spherical zinc in general, although the effect of PVC was varied depending on zinc particle size and shape. For spherical zinc of 6~9μm size, the polarization resistance decreased as the PVC increased. However, the polarization resistance increased for zinc flakes of the same size. Based on the result that lower adhesion correlates with lower corrosion restraint in salt dipping test of 720 hours, ZF1330 (zinc flake, 12~14μm, and 30% PVC) showed the best anti-corrosion performance under all conditions.