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.

The main foundation structure of photovoltaic power generation facilities is a steel pile foundation. Soil corrosion rate is regarded as 0.02 mm/year regardless of the soil. However, it is considered that corrosion rates of each soil are difference. In this study, we estimated the soil corrosion environment by measuring the physical properties of soil and evaluated the charge transfer resistance of each soil environment by AC impedance method that regarded soil as electrolyte, in order to investigate the effect of soil particle size on soil corrosion.

Glass beads of uniform sphere haven’t been packed close-packed structure, and porosity of soil with particle size distribution was nearly equal to regardless of particle size. But in case of the soil that included particles less than 50μm in a large quantity, porosity of the soil was increase. Porosity of soil that had similar particle size distribution was nearly equal regardless of water content. Therefore, it is suggested that the change of soil water content was replacement liquid phase and gas phase. The charge transfer resistance of soil corrosion decreased with decrease of gas phase ratio in soil. Therefore, it is suggested that the charge transfer resistance of soil corrosion might be estimated from the soil particle size distribution and water content.