Long period fiber grating sensors coated with nano iron/silica particles for corrosion monitoring

In this study, a novel long period fiber grating (LPFG) sensor coated with a thin film of nano iron and silica particles is proposed, designed, and tested for corrosion and environmental monitoring. Nano iron particles were introduced to facilitate the monitoring of the corrosion rate while nano silica particles were added to improve coating transparency and robustness. Proof-of-concept tests have demonstrated that the coated thin film did not affect the sensitivities of either the intensity or wavelength of the LPFG sensor to temperature and pH values. However, the resonant wavelength of the coated LPFG sensor increased as iron particles were gradually corroded away. Therefore, with a parallel LPFG sensor for nearby temperature and pH measurements, the proposed novel sensor can measure the corrosion rate of nano iron particles and, once calibrated and correlated, provide critical information about a nearby reinforcing steel bar and structural member. (paper)