A Simulation of Pulsed Eddy Current Testing for Detecting Local Thinning in Corrosion-Resistant Coated Steel Plates

This study investigated the interaction between magnetic fields and eddy currents in locally thinned regions of corrosion-resistant coated steel using pulsed eddy current testing (PECT). Protective coatings on steel components often develop cracks and delamination, allowing moisture to penetrate and cause subsurface corrosion and thinning. Traditional eddy current testing using AC excitation is limited in detecting such defects due to increased lift-off and magnetic attenuation from the coating. To overcome these limitations, PECT — which generates broadband magnetic fields with low-frequency components — was employed. Numerical simulations using COMSOL Multiphysics were conducted on steel models with thinning rates of$10 \%, 20 {\%}$, and 30%, and varying lift-off distances from 1 mm to 20 mm. The results clarified how lift-off and thinning depth influence magnetic field behavior and the detectability of thinning beneath coatings.