Aging Behavior of Fluorocarbon Polyurethane and Epoxy System Coating for Carbon Steel under Subtropical Monsoon Climate

Outdoor exposure tests were carried out on fluorocarbon polyurethane and epoxy coating for carbon steel under subtropical monsoon climate in Guangzhou, in order to study the aging characteristics of the coating. The aging behavior of the coating was analyzed by the electrochemical impedance spectrum and micro morphology of the coating after outdoor exposure for different periods of time. The failure behavior of the coating after damage was analyzed with the surface potentials of the micro-area in cross-cutting sample. The results showed that the coating had a good anti-aging property and protective effect on the substrate under subtropical monsoon climate. After 12 months of outdoor exposure test, the coating did not fail, but there were micron-sized pores in its surface, so the impermeability of the coating decreased. With the increase of outdoor exposure time, the metal substrate in the damaged part of the coating quickly corroded, and the failure behavior gradually expanded to the coated area under the action of corrosion products.