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| Failure Behavior of Epoxy Coatings in Seawater at Different Temperatures |
| Received:October 30, 2018 Revised:April 25, 2019 |
| View Full Text View/Add Comment Download reader |
| DOI：10.7643/ issn.1672-9242.2019.04.021 |
| KeyWord:epoxy coating seawater different temperature electrochemical impedance spectroscopy equivalent circuits |
| Author | Institution |
| WANG Ling |
1. China Weathering Test and Research Center of Science Technology and Industry for National Defense, Southwest Technology and Engineering Research Institute, Chongqing , China |
| LU Zhong-hai |
2. College of Chemistry & Chemical Engineering, Yantai University, Yantai , China |
| LIU Jie |
2. College of Chemistry & Chemical Engineering, Yantai University, Yantai , China |
| HE Jian-xin |
1. China Weathering Test and Research Center of Science Technology and Industry for National Defense, Southwest Technology and Engineering Research Institute, Chongqing , China |
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| Abstract: |
| Objective To study failure behaviors of epoxy coatings in seawater at different temperatures. Methods EIS tech-nique was used to study the EIS characteristics of coatings in two seawater environments. Meanwhile, changes of coating re-sistance and coating capacitance were analyzed to study protective properties of the epoxy coatings with immersion time. Results When the coating was immersed in seawater at 15 ℃ for 1440 h, the impedance value dropped below 106 Ω?cm2; while the impedance value dropped to 106 Ω?cm2 when the coating was immersed for only 72 h in seawater at 30 ℃. With the increase of immersion time, the EIS of the coating immersed in seawater at 15 ℃ changed from a single capacitive loop to double capacitive loop, and the EIS of the coating immersed in seawater at 30 ℃ firstly evolved from a single capacitive loop to double capacitive loop, followed by obvious Warburg resistance characteristic. When the coatings were immersed in seawater at two temperatures, the coating capacitance presented a rising tendency, and the coating resistance showed a decreasing tendency. Conclusion The degradation rate of epoxy coatings in seawater at 30 ℃ is accelerated, which is attributed to that the high temperature reduces the binding force between the coating and the metal, and speeds up the rate of permeation of seawater into the interior of the coating. As the temperature rises, the diffusion process of dissolved oxygen is also accelerated, and thus the oxygen diffusion process becomes a control step of the corrosion reaction, which leads to obvious Warburg resistance characteristics of the EIS of the coating immersed in seawater at 30 ℃. When the epoxy coating is immersed in seawater at 15 ℃ and 30 ℃ for 1800 h, the changes of protective properties could be divided into three stages: rapid decline, slow decline, and stabilization. |
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