抄録
Impedance characteristics of corrosion at asphalt-sand/steel interface were studied on laboratory scale tests and model tanks of 2m in diameter. The equivalent circuit and impedance were interpreted in a similar manner to the under film corrosion of coated steels. Degradation of asphalt-sand layer was evaluated from decrement of film resistance Rf, and the corrosion rate was estimated qualitatively from the impedance Rcor measured at the lowest frequency range around or less than 10mHz. It was confirmed that the main factors to increase the corrosion rate of tank bottom were penetration of water precipitated and oxygen into the asphalt-sand/bottom plate interface. The two frequencies impedance method, proposed previously by the authours, can be applied as monitoring corrosion of fuel tanks, being supported by these impedance characteristics.
