Detection of Early-Stage Corrosion on Coated Structural Steel Using the Hyperspectral Imaging in SWIR Range

Protective coating on steel fails when it ages and under continuous atmospheric influences. When it becomes vulnerable, corrosion begins to form on the coating and even infilters inside corroding the steel underneath the coating. This present study reports the feasibility to use a hyperspectral imaging system in short-wavelength infrared (SWIR) range for detection of early-stage corrosion on the protective coating. Corroded specimens prepared in the laboratory environment and onsite extracted from in-service electricity transmission tower were tested. Experimental results suggest that the spectral response of early-stage corrosion formed on the coating is unique. The corrosion on the coating shows higher reflectance at 1326 nm and lower reflectance at 980 nm than that of the pristine section. Also result shows a correlation between the severity of surface corrosion and the recorded spectral response.