Monitoring Steel Bar Corrosion in 3.5 wt. NaCl Solution Using a Fiber Optic Corrosion Sensor

摘要

In this study, a Fe-C coated LPFG corrosion sensor was employed to monitor corrosion of steel bar in 3.5 wt.% NaCl solution. This corrosion sensor was coated with an inner silver layer and an outer layer of Fe-C coating. The inner silver was sputter coated with a thickness of 800 nm, and the outer Fe-C layer was electroplated with a thickness of 20 μm. A steel bar was cut, prepared and tested in 3.5 wt.% NaCl solution, together with the fiber optic corrosion sensor. The corrosion evolution of both the outer layer of Fe-C coating and the steel bar were investigated with electrochemical impedance spectroscopy (EIS), and the change in the transmitted spectrum of the Fe-C coated LPFG was recorded with an optical sensing interrogator. EIS results showed that the corrosion behavior of steel bar remained stable throughout the whole test period, while the corrosion resistance of Fe-C layer gradually increased with time. Due to the limitation of interaction range between the coating layer and the light propagating in the fiber as well as the coating thickness, this fiber optic corrosion sensor can only monitor the corrosion of steel bar for 18 hours in 3.5 wt% NaCl solution.