Relationship between degradation characteristics of organic coating on internal bottom plate of oil storage tank and constant-phase element parameter values

A quantitative evaluation method is proposed based on electrical impedance measurements for predicting the residual lifetime of a high-performance anticorrosion organic coating on the internal bottom plates of oil storage tanks. The field data obtained from an actual oil storage tank suggest that the impedance characteristics of the degradation of the coating were elucidated by three equivalent circuit models including two CPEs (constant-phase elements) in parallel. It was revealed that these CPEs indicate the intact and the deteriorating coatings. In addition, the degradation process of the coating with age can be monitored quantitatively by using scatter diagrams of CPE parameters.