EddyCurrentTests

Eddy current testing (ECT), also called eddy current tests, is a non-destructive method for evaluating conductive materials. An alternating current in a probe coil generates a changing magnetic field that induces eddy currents in the test piece. Flaws, changes in conductivity or permeability, and geometric variations alter the eddy current flow and produce measurable changes in the coil impedance or signal phase.

ECT uses various probes: surface, differential, encircling coils, and arrays. Techniques may be impedance-based, phase-based, or multi-frequency, enabling depth-sensitive inspection. Non-contact or light-contact methods are common, allowing fast, in-process testing.

Applications include aerospace tubing and skins, automotive components, power plants, and other metal parts. It is especially effective for near-surface cracks, corrosion under insulation, and coating or thickness variations on conductive substrates.

Advantages: rapid, sensitive to small surface and near-surface flaws, suitable for complex geometries, minimal preparation, and compatible with automation.

Limitations: limited depth sensitivity; mainly applies to conductive materials; ferromagnetic materials can complicate interpretation; lift-off and surface condition affect results; requires calibration and skilled analysis.

Standards: procedures and calibration are guided by standards from ASTM International and ISO for eddy current testing.