Abstract: The corrosion behavior of Q420 carbon steel in the atmospheric environment of Yajiang and Litang areas in Sichuan Province after 1 year of exposure was studied through exposure tests, macro morphology observation, Raman spectroscopy analysis, and electrochemical testing. The results showed that after being exposed to the atmospheric environment for one year in both regions, there was a significant rust layer on the surface of carbon steel. The average corrosion rates in Yajiang and Litang were 23. 75 g/(m² ·a) and 8. 48 g/(m² ·a), respectively. After 1 year of exposure to sunlight, the corrosion products on the surface of carbon steel were mainly composed of γ-FeOOH, α-FeOOH and γ-Fe₂O₃, α-Fe₂O₃ appeared in corrosion products after corrosion in the Litang area. The surface corrosion product resistance and surface charge transfer resistance of the steel in the Litang atmospheric environment were both higher than those in the Yajiang atmospheric environment. That means that, after exposure to sunlight for 1 year in the Litang environment, the surface corrosion product of the sample had a relatively good protective effect on the substrate, which could slow down further corrosion of the carbon steel surface.