What Is Eddy Current Testing?
Eddy Current Testing (ECT) is an electromagnetic NDT method that uses an alternating current
driven coil to induce circulating electrical currents — eddy currents — in an electrically
conductive material. Discontinuities in the material alter the flow of these eddy currents,
producing measurable changes in the probe's impedance that are detected, displayed, and
interpreted by the ECT instrument.
Key characteristics of ECT:
- No couplant required — completely dry, contact or near-contact inspection
- Effective through thin non-conductive coatings (paint, anodising) up to several millimetres
— no need to remove the coating for screening inspection
- High sensitivity to surface-breaking cracks — particularly fatigue cracks and stress
corrosion cracks
- Rapid scanning speed for surface survey applications
- Applicable to non-ferromagnetic materials (austenitic stainless steel, aluminium, titanium,
copper alloys) where MT is not available