Influence of Rainfall on Atmospheric Corrosion Behavior of Carbon Steel

A combined cycle corrosion test including the conditions simulating rainfall was conducted to investi gate the effect of rainfall on the atmospheric corrosion behavior of carbon steel. Atmospheric corrosion sensors developed were used as the electrodes, and the corrosion rate during the corrosion test was monitored by an electrochemical impedance method. The corrosion rate was monitored by continuously measuring the impedance at low frequency (10 mHz) and high frequency (10 kHz) at 5-minute intervals. The corrosion rate of corrosion sensor exposed to the corrosive environment without a rainfall process showed a high value in a salt spray process, and dropped sharply after proceeding to the drying process. The salt deposited on the sensor surface absorb moisture in the wet process, resulting that the corrosion rate increased again. This change in corrosion rate was almost the same at the beginning of corrosion and after the for mation of corrosion products. The corrosion sensors exposed to rainfall process gave very high corrosion rates after rainfall. Although The corrosion sensor with the rainfall process for 1 minute showed a higher corrosion rate in the early stage of corrosion, there was no difference in the corrosion rate due to rainfall time after the formation of corrosion products. Analysis of corrosion products showed that the attached salt was washed away by rainfall. However, in this study, the wetting due to rainfall greatly affected the corrosion rate of carbon steels.