Glossary

Eddy Current Testing (ECT) is a non-destructive testing (NDT) method that relies on electromagnetic induction to detect flaws in conductive materials. A probe containing a coil is energized with alternating current, which generates a changing magnetic field. When the probe is brought near a conductive material, this field induces circulating electrical currents—called eddy currents—at the surface. These eddy currents in turn produce their own opposing magnetic fields, which alter the electrical impedance of the probe’s coil. If the material is free from defects, the eddy currents flow in a predictable way. However, when there is a discontinuity such as a crack, corrosion pit, or thinning of the material, the flow of eddy currents is disrupted, and the resulting change in coil response is measured and displayed on an instrument.

ECT is widely used in aerospace, power generation, and manufacturing industries for detecting cracks in aircraft skins, measuring tube wall thickness in heat exchangers, inspecting welds, and monitoring corrosion under paint or thin coatings. It has several advantages: it is fast, highly sensitive to small surface-breaking flaws, requires little or no surface preparation, and can even detect defects through thin coatings. Unlike ultrasonic testing, it does not require couplants, and unlike radiographic testing, it does not involve radiation. However, it does have limitations: it only works on electrically conductive materials, its penetration depth is shallow (best for surface and near-surface defects), and accurate interpretation depends heavily on the skill of the operator and proper calibration with reference standards. Despite these constraints, ECT remains an essential inspection method wherever precision, speed, and sensitivity are required.