Abstract
Generally, the organic coating on bottom plate of oil storage tank is used in corrosion protection. However, the coating degrades with a long time. The degradation of the coating is one of important factor which dominates the inspection period of the oil storage tank like the back-side local corrosion. As the technique to evaluate the degradation of organic coating, appearance inspection, adhesion test (pull-off test) and electrical characteristics evaluation by impedance measurement is done. The impedance method is a nondestructive inspection technique. Also, because it is very handy to measure, this method is applied as the evaluation of organic coating on bottom plate of oil storage tank. However, in the present situation, the measured data and the analysis result aren't sufficiently utilized in fields. In this study, a lot of impedance data was measured in the place of a wide range of degradation levels. The data is analyzed by the new equivalent circuit model. As the result, correlation between the impedance analysis result and the degradation level was admitted. Therefore, the degradation level could be quantitatively shown.
