What is Eddy Current Testing?

Overview

Eddy Current Testing (ECT) induces small electrical currents in a conductive material. A crack or flaw disturbs these currents, which the instrument detects. ECT may inspect through suitable non-conductive paint or coatings, making it useful for rapid screening when lift-off and surface condition are controlled.

It can be useful for fatigue-crack screening on conductive components such as elevated work platforms and cranes. The response is affected by conductivity, permeability, lift-off, probe frequency, geometry and the depth and orientation of a discontinuity.

What ECT Detects

• Surface and near-surface cracks
• Fatigue cracking at welds
• Cracks through paint and coatings
• Conductivity and coating thickness

When ECT Is a Good Fit

ECT is useful where a rapid, localised examination of conductive material is needed and removing a non-conductive coating would be undesirable. It is especially useful for repeat screening of known fatigue-critical areas. See how eddy current works for the signal principle.

Limitations and Interpretation

• ECT does not work on electrically insulating materials and magnetic permeability can complicate responses
• Lift-off, coating thickness, edges, fasteners, curvature and weld geometry can mask or mimic indications
• Sensitivity decreases with depth; a claim that ECT works through paint does not mean every coating or condition is suitable
• Signals require calibration, qualified interpretation and comparison with relevant reference indications
• ECT is not a general volumetric examination; use UT or another suitable method when internal coverage is required

Related Inspection Scope

For a commercial inspection scope, see eddy current testing services, crack detection or EWP inspection.