Eddy current testing (ECT) is one of the most versatile NDT methods, and your summary covers its main applications well. Here are some additional points that might help members working with it:

ECT works by inducing alternating electrical currents into a conductive material using a probe coil. Changes in the material's electrical and magnetic properties — caused by defects, changes in composition, or physical condition — alter the impedance of the coil, and these changes are detected and displayed as signals. Because it works only on conductive materials, ECT is particularly useful for metals.

Key advantages:

- Rapid inspection with no coupling medium needed
- Excellent sensitivity to small surface and near-surface defects
- Can inspect through thin coatings without removing them
- Portable equipment allows on-site testing
- Can measure coating and material thickness accurately

The method does have limitations. Depth of penetration depends on frequency, material conductivity and permeability, so deeper defects may be harder to detect. Surface finish and material composition variations can affect readings, sometimes making interpretation challenging. Thick materials and ferromagnetic materials require careful setup and technique.

When using ECT, always follow your written procedure and the applicable code or standard — ASME Section V, ISO 15549, or your customer's specification — which will define probe selection, calibration standards, scanning speed, signal interpretation and acceptance criteria. The responsible Level III or authorised inspector should oversee technique validation and acceptance decisions.