The application of a lining on the inner surface of steel single-shell underground oil storage tanks (USTs) is effective as a corrosion prevention measure, but its anti-corrosion performance decrease over time. Therefore, it is necessary to evaluate the lifetime of the lining in terms of the anti-corrosion performance by using non-destructive inspection. However, the definition of the lifetime and its relationship to numerical values of the non-destructive inspection is not clear. In this study, the electrical property and the adhesion of the inner lining in contact with petroleum fuel for a long period was investigated. The anti-corrosion performance degradation of the lining was evaluated based on the glass flake coating’s evaluation standard of HPIS G105 TR(2017).
Based on the tan
δ1kHz, which is one of the electrical properties, the lining was evaluated as good in all samples. On the other hand, the lining was evaluated as poor in some parts in terms of the adhesion. The lining inside the tank swells due to petroleum fuel, causing damage to the lining’s resin itself and the lining/steel plate interface. This leads to poor adhesion. However, because there would be little water and ions inside the tank that cause active corrosion and decrease electrical property, tan
δ is difficult to decrease. Thus, it is thought that the degradation of the adhesion occurs before that of the electrical property in the inner lining of USTs. If degradation in the anti-corrosion performance of the lining is defined as a decrease in the adhesion due to swelling, it is possible to quantitatively evaluate the anti-corrosion performance by using the speed of sound of ultrasonic, which is a non-destructive inspection value linked to swelling.
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