Defect mapping of steel substrate under fire protection layer using EM NDE methods

Accurate and reliable defect detection and characterization of structures and critical components is becoming of increasing importance. Electromagnetic (EM) methods like eddy current (EC), electromagnetic acoustic transducer (EMAT), alternating current field measurement (ACFM) and microwave imaging have lend credence to this search for a reliable defect detection and characterization probe. However, a probe that would exhibit high sensitivity and spatial resolution in detecting corrosion of substrate under fire protection layer (FPL) with relatively high liftoff is desirable. This paper therefore presents a comparative investigation of the potentials of eddy current displacement sensor and microwave imaging in detecting corrosion in cladded steel samples of varying clad thickness. The possibilities and potentials of these EM NDE techniques for defect-under FPL detection are brought to light in the results presented.