Abstract
Degradation of aged power transmission systems have become a serious problem in Japan. In the case of a transmission tower, inner corrosion of the steel pipe beam is one of the issues because internal corrosion assessment based on the external appearance of the pipe is difficult. In order to utilize practical inspection techniques, characterization of the corrosion properties of the pipe, especially of the internal surface, is required. In this study, several atmospheric corrosion (ACM) sensors were arranged at a regular interval inside steel pipes which were set up at a coastal testing field and the time dependence and corrosion rate distribution of the inner surface of the pipes from the end to the center were evaluated. Based on the study it was concluded that the corrosion behavior of the inner section of the steel pipe strongly depends on climatic conditions such as temperature, dew point, relative humidity, rainfall and wind direction. The corrosion rate tends to become less from the end to the center inside the steel pipe. The corrosion information acquired from ACM sensors showed good agreement with the corrosion condition of the steel pipe sample, which indicates that the method used in this study is effective for monitoring the internal corrosion status of steel pipes.
