Which defect is least likely to be detected by Eddy Current Testing?

Eddy Current Testing (ECT) primarily detects surface and near-surface defects due to its reliance on electromagnetic induction. The technique is highly sensitive to small changes in conductance and permeability, which are often associated with surface anomalies.

Embedded voids in solid metals are typically located deeper within the material, well beyond the reach of the electromagnetic fields generated by eddy currents. Since ECT is designed to identify discontinuities at or near the surface, its effectiveness diminishes significantly with defects that are buried or located away from the surface.

In contrast, surface cracks, inclusions, and lap defects, all of which can originate and manifest at or close to the surface, are more readily detectable through ECT. This is because the test relies on changes in the flow of eddy currents caused by these types of discontinuities, allowing operators to identify issues effectively.