Cailiao Baohu (Aug 2022)

Study on Corrosion Behavior of Acrylic Powder Coating in Simulated Marine Atmospheric Environment

  • YU Qiang, XIANG Ji-ming, ZHANG Li-wen, ZHANG Li-ming, ZHOU He-rong

DOI
https://doi.org/10.16577/j.issn.1001-1560.2022.0210
Journal volume & issue
Vol. 55, no. 8
pp. 22 – 30

Abstract

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Acrylic powder coating has excellent anti-aging function and often used as an environmentally friendly topcoat coating. In order to understand its anti-corrosion performance and anti-corrosion mechanism for the purpose of expanding its application, the corrosion behavior and mechanism of intact acrylic powder coatings in marine environment and the defect of acrylic powder coating had been investigated using CASS test, immersion test and AC impedance method. Results showed that the transparent acrylic powder coatings with a thickness of 80 μm and 120 μm respectively had a few blisters on the edge of the scratch after treated by a 240 h CASS test. For the powder coating with a thickness of 120 μm, the maximum and minimum widths of corrosion products around the scratch were about 3.5 mm and 0.5 mm respectively, and the adhesion to the surface was level 0, indicating that the coating had good CASS resistance. After an immersion of 30 d, the amount of corrosion products generated around the scratch of 120 μm coating was smaller than that of 80 μm coating, revealing that 120 μm coating had better immersion resistance. Furthermore, the EIS of scratch specimens in 0.6 mol/L NaCl solution showed that the electric double layer capacitance decreased rapidly firstly and then tended to be stable, and the corrosion rate increased with the prolonging of immersion time. The impedance of the intact acrylic powder coating decreased from about 1010～1011Ω·cm2 to 106 Ω·cm2 after an immersion in 0.6 mol/L NaCl solution for 720 h. The barrier effect of these two kinds of coatings was basically the same after a 360 h immersion. Besides, as the aluminum alloy material covered with acrylic powder coating had poor corrosion resistance, the acrylic powder coating was not suitable to be used alone as the coating system for the automobile aluminum wheel hub or the alumimum alloy material. Hence, it is recommended to use composite coating system as the coating scheme for automobile aluminum alloy wheel hub.

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