Evaluation for Properties of Anti-Corrosion Epoxy Coating after Photo-Oxidation Aging

摘要

In this article, a set of aging anti-corrosion epoxy coating was prepared in Xenon lamp light chamber of Oh, 72h, 144h, 216h, 288h, 360h and 432h. Meanwhile, the changes adhesion properties, functional groups, and corrosion resistance properties increasing with aging time were determined. The results showed that the thickness of epoxy coating was increased more than 50% as the aging time increased to 432h, and reached 32um. The adhesion reduced significantly, which was 0 grade in cross-cut test at Oh, but decreased to 2 grade after been aged for 432h. Meanwhile, the value of adhesive force declined more than 56% in pull-off test. The corrosion resistance properties were investigated by electrochemical impedance spectra (EIS) in both 3.5% NaCl neutral solution (pH=7) and acid solution (pH=2). The Nyquist plots in neutral solution transferred from single time constant to two time constants in neutral solution. The capacitive impedance loop became shorter, while coating resistance Rf declined more rapidly as the aging time increasing. Meanwhile, the Nyquist plots possessed three time constants in acid solutiondue to the dissolution of zinc in the coating. The FT-IR spectrum showed that the peak value of C-O-C and C-H declined with aging time increasing, and the peak of C=O becamemore significantly. The results showed that the protective properties of epoxy coating declined while the aging reaction going on, with chain broken of C-O-C and C-H bond and hydrophilicity enhancing.