A reasonable evaluation method is proposed based on an extreme value analysis for the appropriate management of a high−performance anticorrosion organic coating applying to the internal surfaces of the bottom plates of oil storage tanks.The analysis was applied to the values of constant−phase element(CPE)parameters extracted from the field impedance data obtained from the actual oil storage tanks.It was found that the representative degradation characteristics of the coating before the

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... of visual defects can be evaluated by using the probability plots of the maximum values. In addition,the comparative evaluation of the degradation degree of the coatings between oil storage tanks was performed using this method.