The atmospheric corrosion performance of carbon steel exposed in Warming area, which located in the south part of China with tropic marine environment characters, was studied at different exposure periods (up to 2 years). To investigate the effect of beta-FeOOH on the corrosion behavior of carbon steel in high chloride ion environment, rust layer was analyzed by using infrared spectroscopy, scanning electron microscope, X-ray diffraction, and the rusted steel was measured by electrochemical impedance spectroscopy method. The weight loss test indicated that the corrosion rate of carbon steel sharply increased during 6 months' exposure and gradually reduced after longer exposure. The results of rust analysis revealed that the underlying corrosion performance of the carbon steel was dependent on the inherent properties of the rust layers formed under different conditions such as composition and structure. Among all the iron oxide, beta-FeOOH exerted significant influence. The presence of a monolayer of the rust as well as beta-FeOOH accelerated the corrosion process during the initial exposure stage. EIS data implied that beta-FeOOH in the inner layer was gradually consumed and transformed to gamma-Fe2O3 in the wet-dry cycle, which was beneficial to protect the substrate and reduced the corrosion rate. (C) 2008 Elsevier B.V. All rights reserved.