Eddy Current vs. Ultrasonic Testing: Which is Best for My Application?

Consider whether eddy current or ultrasonic is best for each application.

When it comes to eddy current vs. ultrasonic testing (UT), both technologies can deliver quality data. However, there are certain situations where one method is better than the other. For instance, eddy current testing (ECT) is more conducive to flatter welds and surface flaws than ultrasonic testing. On the other hand, ultrasonic testing is better at detecting flaws on a volumetric level, including thicker welds.

This article will explore some other pros and cons of ultrasonic and eddy current techniques.

Ultrasonic Testing Advantages

The main advantage of ultrasonic nondestructive testing (NDT) is the depth penetration, and advanced methods like phased array ultrasonic testing (PAUT) provide additional flexibility during the inspection process. In addition, ultrasonic testing with phased array comes with the following benefits:

The ability to inspect a wide range of materials and geometries, while ECT is optimized to inspect conductive materials.
Ideal for inspection of welds, thickness and dimensional measurement, corrosion and flaw detection.
Capacity to inspect subsurface flaws on a volumetric level and provide diverse angles from a single probe.
Enhanced flaw characterization via beam shaping and beam tailoring.
Electronic optimization to augment focusing depth.

Like UT, ECT also has customization procedures but not when it comes to achieving a more comprehensive scan on a subsurface level. Moreover, UT is often more desirable because it can analyze larger areas in a single testing campaign and the complexities of certain welds that are more challenging for ECT.

Eddy Current Testing Advantages

Eddy current testing is often the preferred option when inspecting tubes and surface flaws like cracking. Eddy current instrumentation, for example, can come with simultaneous and multiplexed injections in a single box to test many types of tubing materials, including magnetic alloys like carbon steel. Advanced tubing probes can integrate bobbin and array technologies together for greater flexibility, inspection speed and quality data. An advanced ECT technology campaign excels in detecting extremely small surface defects, inspecting non-flat surfaces, and covering a wide area in a single pass.

Quality eddy current equipment can also achieve the following:

Additional coverage with array coils in probes, reduces the number of probe changes and provides quality data with a single pass of the probe
Conductivity and thickness measurements on alloys and metals
Measurement and probing of coated surfaces
Multi-layer corrosion inspection using exceptional signal-to-noise ratio
Powerful surface array abilities in a handheld device

In addition, ECA has several advantages such as fast inspection, improved detection capability, accurate flaw positioning and sizing, making it an ideal choice for many aerospace, oil and gas inspection applications.

Eddy Current vs Ultrasonic Testing: What’s the Verdict?

The question of eddy current vs ultrasonic testing comes down to the type of material being tested and the inspection application. Eddy current is usually the best technique when inspecting tubing materials, thinner welds, and surface flaws, whereas ultrasonic technology is a good choice when assessing corrosion, wall sizing and thicker forms of welding that may harbor deviations on a volumetric level.

Even though eddy current and ultrasonic testing have their limitations, these setbacks can be overcome with quality equipment and software made by a trustworthy NDT provider. With the right solution and approach, eddy current and ultrasound can find more flaws safer and at times quicker than other NDT techniques, such as magnetic particle testing or liquid penetrant testing. Eddy current and ultrasound can find early forms of deviations sooner rather than later, allowing maintenance departments to commence the necessary repairs to avoid hazards and ensure safety.

Zetec is a major provider of eddy current and ultrasonic equipment for surface and subsurface indications. Contact us today to get a custom inspection plan and quality equipment.