Atmospheric corrosion monitoring in each part of model structure using AC impedance method

AC impedance method has been applied to evaluate the corrosion resistance in each part of the steel model structure exposed to outdoor environment. The corrosion sensors, which were made of the same materials as the steel model structure, were installed to each part of the model structure. The impedances at 10 kHz and 10mHz were continuously measured between the steel model structure and the corrosion sensors, and the corrosion rate was obtained by subtracting the impedance at 10 kHz from at 10 mHz. The corrosion rate and the solution resistance in each part of the steel model structure were greatly influenced by the environmental factors. While rain and dew condensation were observed, the low solution resistance and the high corrosion rate were measured in all parts of the steel model structure, indicating that the corrosion progresses due to the wetness of the surface. From the corrosion loss in each part of the steel model structure, the horizontal parts showed larger corrosion loss than the perpendicular parts, and the tendency was stronger in flange part than in roof part. The change in impedance and the corrosion loss suggested that the corrosion behaviors in each part of the steel model structure are different.