The durability of a steel floodgate can have disadvantage to corrosion damage, because it is often come in contact with high humidity condition. In this study, to evaluate the corrosion rate depending on installation environment of a steel floodgate, atmospheric exposure test was performed using corrosion environment measurement sensors and monitoring specimens. From the correlation between the mean corrosion depth and corrosion current, the corrosion rate was estimated depending on the installed environment for the member of a steel floodgate.