Electrochemical Corrosion Behavior of Carbon Steel Covered by Rust Layer in 3% NaCl Solution

The corrosion behavior of carbon steel in 3% NaCl solution was studied by weight-loss method, infrared spectroscopy (IR) and electrochemical impedance spectroscopy(EIS). The results indicate that the corrosion process of carbon steel is affected by rust layer significantly. The rust layer is composed of γ-FeOOH and Fe3O4. γ-FeOOH can be reduced easily and work as oxidant. The Fe3O4 layer provides a large cathodic area and oxygen can be reduced on the surface of rust layer. As a result, the rust layer can not prevent the corrosion of carbon steel and even can accelerate the corrosion process. The corrosion rate of carbon steel is determined by the limiting diffusion rate of oxygen.