Abstract
The effectiveness of glass-fiber reinforced plastics （GFRP） may decrease with age. This research aims to develop a quantitative health （anti-corrosion performance） diagnosis method of the GFRP that applied inner surface of steel oil storage tanks during open inspections. To achieve this purpose, the degradation characteristics of the GFRP based on an unsaturated polyester resin coated steel plates that have been in contact with petroleum fuels （kerosene, diesel oil, regular gasoline and premium gasoline） for approximately 17 years were investigated by physiochemical techniques. The results of electrochemical impedance spectroscopy measurements which can quantitatively evaluate anti-corrosion performance, show that the electrical properties of GFRP decrease with long-term use. FT-IR measurements suggest that the decrease in electrical properties is due to swelling, where the hydrocarbons permeate inside the resin and open up its network structures. The swelling could also be detected by the longitudinal speed of sound of the GFRP, which is related to mechanical property such as the hardness. Finally, based on the assumption that changes in electrical and mechanical properties are brought about by the swelling, a practical method for estimating anti-corrosion performance of the GFRP in field from the longitudinal speed of sound is proposed.
