Quantification and assessment of steel pitted corrosion using optical frequency domain reflectometry (OFDR)-based distributed fiber optic sensors

Steel corrosion is a widespread issue affecting the integrity and serviceability of infrastructures, industrial equipment, and transportation systems. Distributed fiber optic sensors (DFOSs) based on optical frequency domain reflectometry (OFDR) offer high spatial resolution, distributed sensing ability, and environmental resistance, making them ideally suited for detecting steel corrosion, especially pitting corrosion. This study presents a real-time corrosion detection-based assessment methodology using OFDR-based DFOSs. A practical sensing model was proposed to derive corrosion severity from the strain measurements obtained from distributed sensors, enabling the estimation of pit depth, mass loss, and average corrosion rate. The corrosion conditions of steel specimens were monitored through accelerated corrosion tests using OFDR-based DFOSs, which was further validated against commonly used corrosion detection methods. The experimental results demonstrated an excellent matching in the location and depth of pitting corrosion, mass loss, and corrosion rate between the well-established detection techniques and the proposed methodology, indicating the accuracy and effectiveness of DFOSs in assessing corrosion. Specifically, the pit depths evaluated by DFOS and measured by microscopic scanning predominantly ranged from 13 μm to 22 μm, demonstrating excellent consistency between the two methods. The maximum pit depths evaluated by DFOSs for the three specimens were 27.23 μm, 28.10 μm, and 31.93 μm, respectively. In addition, the DFOS configurations were optimized by examining the effects of deployment spacing and gauge pitch of the DFOSs. This study highlights the potential of DFOSs in steel corrosion evaluation, paving the way for advanced design and practical application of DFOSs in structural health monitoring.