Through coating imaging and nondestructive visualization evaluation of early marine corrosion using electromagnetic induction thermography

Early marine corrosion especially under coating is difficult to be detected, sized and predicted. This work proposed through coating imaging (TCI) based on high frequency electromagnetic induction, thermal wave propagation and infrared temperature field measurement. The proposed method is called electromagnetic induction pulsed phase thermography (EMIPPT), whose advantages include being nondestructive, non-contact, fast speed, large-area, high resolution and visualization. By phase analysis, the complex influence of parameter variation on temperature can be eliminated and then relative variation of corrosion height can be characterized. The mild steel (S275) samples providing coated real marine atmosphere corrosion with exposure from 1, 3 and 6 months were tested. The experimental results illustrate that EMIPPT has greater potential for in-service corrosion detection, sizing and monitoring than laser profilometry, pulsed eddy current, and microwave waveguide.