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Abstract

This study explores the weather resistance, mechanical properties and corrosion resistance of polyurea coatings in marine environments. The relevant analysis results can be used as a reliability assessment of offshore wind turbine structural coatings during their service life under the influence of marine environments. The long-term experiment uses seawater and 70°C thermal aging conditions as coating reliability assessment items. The microstructure of the samples that have been immersed in seawater for a long time and thermally aged is observed using a scanning electron microscope (SEM). The results show that the surface of the 100 and 125 series polyurea coatings is flat at the beginning of the seawater corrosion test (96 hours). At this time point, the polyurea coating will be accompanied by the phenomenon of mechanical property recovery (i.e., the mechanical properties are improved). When the test time is increased to 168 hours to 3 months, precipitates will appear on the coating surface and holes will form; when the test time is increased to 5-12 months, wrinkles and holes will appear on the test piece. After the functional group detection by Fourier transform infrared spectroscopy (FTIR), the spectrum shows that the peak at a frequency of 3300 cm⁻¹ belongs to the stretching vibration reaction of the N-H bond, and the peak intensity of the N-H bond will weaken as the test time increases. The peak at a frequency of 1660–1620 cm⁻¹ belongs to the carbonyl bond. The test results show that the carbonyl bond peak will shift as the test time increases. This shift belongs to the reaction of hydrogen bond aging and dissociation. Finally, the mechanical property test results show that the mechanical property retention rate of the coating can be maintained at more than 80% after long-term testing. The results of the QUV test and the marine exposure test show that the corrosion rate of the steel pile coating in the marine environment is only 0.00141 mm/year, the weight loss is 0.076%, and there is no significant peeling on the coating surface, only seaweed and shells are attached. The actual results of marine corrosion show that the polyurea coating has excellent corrosion resistance and has long-term stability in harsh marine environments, and can be used as an outer protective layer for marine structures.

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