Advancements in Deterioration Detection for Steel Bridge Anticorrosion Coatings via Short-wavelength Infrared Hyperspectral Imaging

Abstract

A long in-service period of steel bridges can be achieved through a comprehensive approach that involves clarifying the corrosive environment, understanding the rate of deterioration caused by corrosion, and designing appropriate repairs. Therefore, monitoring systems to predict the deterioration of infrastructure structures and nondestructive testing methods to evaluate the degree of deterioration have been developed. This study introduces short-wavelength (SW)-infrared hyperspectral imaging as a method for detecting deteriorated areas in the top coats of anticorrosion systems with unknown infrared spectral properties. Deteriorated regions on in-service bridge coatings are identified by selecting specific wavelengths that exhibit significant differences in infrared reflection intensity within the SW-infrared spectrum. Moreover, measurements of SW-infrared hyperspectral imaging obtained using a maintenance vehicle were nearly as accurate as those from the motorized stage, indicating the imaging systemʼs potential to detect early-stage deterioration during routine maintenance. Additionally, the spectral lock-in method—which employs a lock-in process to extract synchronous components from a reference signal—is demonstrated as an effective technique for identifying top coat deterioration based on distinct variations in the spectral properties of the coatings.