| QI Xiao-yu,WANG Tao,WEI Li,FAN Cai-quan,CUI Zhong-yu,MAN Cheng,WANG Xin,CUI Hong-Zhi.Failure Behavior of Epoxy Coatings in Low Temperature and Ultraviolet Environment[J],52(12):408-418 |
| Failure Behavior of Epoxy Coatings in Low Temperature and Ultraviolet Environment |
| Received:December 02, 2022 Revised:February 21, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.12.035 |
| KeyWord:epoxy coating polar regions low temperature ultraviolet failure |
| Author | Institution |
| QI Xiao-yu |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| WANG Tao |
Polar Research Institute of China, Shanghai , China |
| WEI Li |
Polar Research Institute of China, Shanghai , China |
| FAN Cai-quan |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| CUI Zhong-yu |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| MAN Cheng |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| WANG Xin |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| CUI Hong-Zhi |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
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| Abstract: |
| The failure behavior and mechanism of epoxy zinc-rich coatings (EP-Zinc) and epoxy wear-resistant fast drying coatings (EP-WR) in ultraviolet (UV) and low temperature environments were studied in this work. The Q235 steel was used as the base material, and the coating was sprayed on the substrate surface with an airbrush. The two coating systems were put into a drying oven and kept at 60 ℃ for 1 day, and then were placed at the room temperature for 6 days to ensure that the organic solvent inside the coating was completely volatilized. The failure behavior and mechanism of epoxy coatings were studied by means of ultraviolet radiation and low temperature exposure, open circuit potential test, electrochemical impedance test, infrared spectrum test, surface characterization (SEM), and adhesion test. The results showed that the failure of the epoxy coating failed in the low temperature environment was mainly due to the large difference between the thermal expansion coefficient and the metal substrate, which resulted in the stress caused by the difference in volume between the coating and the metal substrate. The EP-WR coating produced tiny holes on the coating surface, resulting in the unsmooth coating surface. The ultraviolet (UV) environment changed the chemical structure of the coating surface, leading to the formation of the holes, cracks, and other microscopic defects within the coating. The electrochemical test results showed that the protection ability of the two coatings decreased in the ultraviolet (UV) and low temperature environment. The open circuit potential of the two coatings decreased and fluctuated with the extension of aging time, indicating that the electrochemical activity of the system increased, and the protection performance decreased. In the ultraviolet (UV) environment, the modulus values of the EP-Zinc and EP-WR coating decreased to 106 Ω.cm2 and 107 Ω.cm2, respectively. In the low temperature environment, the modulus values of the two coatings decreased to 106 Ω.cm2 and 105 Ω.cm2. In addition, adhesion played an important role in the failure behavior analysis of coatings. In the low temperature environment, the adhesion of the EP-Zinc coating decreased from 5.92 MPa to 4.97 MPa, and that of the EP-WR coating decreased from 6.51 MPa to 4.94 MPa. This indicated that the damage to the interfacial bonding strength between the coating and the substrate was relatively small in the low temperature environment. In the ultraviolet (UV) environment, the adhesion of EP-Zinc and EP-WR coatings had similar changes, and both of them showed a large decrease with the extension of ultraviolet irradiation time, among which the EP-Zinc coating adhesion decreased from 5.92 MPa to 2.02 MPa and the EP-WR coating adhesion decreased from 6.51 MPa to 3.44 MPa. FT-IR results showed that both EP-Zinc and EP-WR epoxy coatings produced similar characteristic peaks in 1 708-1 736 cm–1 in the UV environment, which was the stretching vibration peak of carbonyl group in saturated aldehydes, ketones and acids, indicating that aging occurred. However, no new bond was formed in the low temperature environment. The failure of coatings in low temperature environment is mainly caused by the change of physical factors, and the failure of coatings in ultraviolet environment is mainly due to the change of chemical factors. |
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