Comparative study on the degradation of a zinc-rich epoxy primer/acrylic polyurethane coating in different simulated atm
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Comparative study on the degradation of a zinc-rich epoxy primer/acrylic polyurethane coating in different simulated atmospheric solutions Wei Sun, Chao Xing, Xiaobo Tang, Yu Zuo, Yuming Tang , Xuhui Zhao
American Coatings Association 2020 Abstract The degradation of a zinc-rich epoxy primer/acrylic polyurethane coating system on carbon steel was studied in the simulated marine atmospheric solution (0.05% NaCl), industrial atmospheric solution (0.35% (NH4)2SO4), and marine-industrial atmospheric solution (0.05% NaCl + 0.35% (NH4)2SO4), by electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy methods. The influences of the soluble contaminants in the atmospheres, including chloride ions, sulfate ions, and ammonium ions, on the coating failure mechanism were compared and analyzed. The results showed that the degradation speed of the coating system in three simulated atmospheric solutions is in the following order: simulated marine atmosphere > simulated marine-industrial atmosphere > simulated industrial atmosphere. The degradation is mainly related to the permeation rate of the water through the coating. The aggressive ions, basic cations, and the property of the corrosion products also have influences on the degradation process. The alternating temperature environment (45C 12 h + 25C 12 h) could increase the degradation speed of the coating and the difference of the speed in the three solutions.
W. Sun, C. Xing, X. Tang, Y. Zuo, Y. Tang (&), X. Zhao (&) Key Laboratory of Electrochemical Process and Technology for Materials, Beijing University of Chemical Technology, Beijing 100029, China e-mail: [email protected] X. Zhao e-mail: [email protected] W. Sun AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China
Keywords Simulated atmospheric solutions, Zinc-rich epoxy coating, Acrylic polyurethane coating, EIS, Degradation
Introduction Organic coatings have been extensively used to protect carbon steels from corrosion in atmospheric environments. However, weathering conditions such as water, oxygen, temperature, and sunlight can cause the degradation of coatings and reduce the service lifetime. The soluble contaminants (mainly chloride ions and sulfur dioxide) in the atmosphere also have negative influences on the coating degradation.1–3 Based on the primary compositions of contaminants, there could be three kinds of atmospheres, which are marine atmosphere containing chloride ions, industrial atmosphere containing SO2, and marine-industrial atmosphere containing both chloride ions and SO2.4–6 Most of the studies on the degradation of organic coatings in atmospheric environments have been carried out on the degradation mechanisms under different accelerated weathering tests,7–10 or the correlations between the accelerated tests and natural exposure tests.11,12 Perrin et al. studied the degradation processes and mechanisms of several anticorrosion coating systems under UV irradiation and neutral salt spray accelerated test c
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