Zetec, Inc

Eddy Current for Thickness Measurement: Why Ultrasonic may be the better choice

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Courtesy of Zetec, Inc

Many of the most complex, large-scale systems also depend on the successful functioning of the smallest components and carefully-calibrated coordination. Tiny flaws or small layers of corrosion can cause huge problems. To ensure product reliability, manufacturers and asset owners run tests frequently. Both wall and coating thickness measurements are among these tests. 

Coating thickness measurement on conductive and non-conductive materials is important to detect abrasion, erosion, or other forms of corrosion in a wide variety of fields. These small layers of wear and tear can be the start of larger issues. Therefore, catching them quickly is key to saving time and resources. 

Nondestructive testing (NDT) is the preferred method for both of these types of materials. Eddy current testing is typically used for nonconductive coatings, and ultrasonic for most standard wall thickness testing measurements. 

In many large-scale manufacturing efforts, using the right equipment for the job is the only way to succeed. When it comes to ultrasound or eddy current testing for thickness measurement, the same is true. Understanding what kind of tools you need can help ensure integrity for years.

Eddy Current for Thickness Measurement: Why Ultrasonic may be the better choice

Eddy Current Testing for Thickness Measurement

Eddy current testing and more recently eddy current array (ECA) is one of the standards of thickness measurement because it can be used for nonconductive coatings on conductive-base materials. By inducing a magnetic field, ECA can read the currents to create a picture of the surface. This helps detect any abrasions. 

There are a few reasons why ECA is such a popular choice for nonconductive materials. 

  • It can determine thickness of non-metallic coatings on magnetic substrates.
  • It doesn’t always need surface contact to get a reading, which can be a huge plus for complicated testing sites.
  • With the right equipment, it can be used to test irregular shapes such as cylinders and rods.
  • With a highly flexible probe, spot checks of targeted areas can be conducted. 
  • It can be used on large surfaces (such as an airplane wing) with relative ease by the testing analyst. 

What’s also important is the rendering of quick results. By using a proper handheld ECA probe and employing sophisticated, easy-to-use eddy current array testing equipment, you’ll have a layer-by-layer picture in almost real-time, allowing you to quickly identify areas of corrosion or abrasion. 

Of course, this is mostly only true if you have the right kind of handheld eddy current instrument. Having the right tool allows you to measure thickness regardless, in a wide array of thickness and conductivity levels. Versatility is the key to proper thickness measurement—especially when testing non-uniform shapes and sizes. 

Not everything measured will be the same. Nonconductive coatings won’t always be an issue. And when they are not, there might be other NDT methods for determining thickness.

The Use of Ultrasonic Testing for Thickness Measurement

Many critical assets, such as those in industrial settings including pipes, vessels and storage tanks will require corrosion mapping or wall thickness measurements. In this case, phased array ultrasonic testing (PAUT) might be the better choice to conduct fast, accurate, and efficient tests. 

A good testing regimen requires the right ultrasonic testing equipment. This entails:

  • an easy-to-use encoded scanner 
  • a portable ultrasonic instrument 
  • intuitive analysis and reporting software

Thickness testing needs to be conducted directly on the surface and sometimes those surfaces are incredibly large. That’s why any instrumentation needs to be easy-to-use for the technician. 

Phased array ultrasonic testing uses sound waves to create a perfect 3D image of the surface layers, which allows the user to see a full picture in real-time. They are essentially scanning the surface and getting a look underneath, layer by layer. 


The right software will not only ensure that no spot is missed, but it can detect minute damages and abrasions completely invisible to the naked eye. 

PAUT testing is portable, cost-effective, saves time, and is wholly accurate. When every millimeter matters—and they always matter—phased array ultrasonic testing is the best way to ensure integrity and effectiveness.

The Right Tools for Thickness Management

Typical thickness measurements demand NDT that is easy to use. While eddy current array testing is invaluable when dealing with nonconductive coatings, phased array ultrasonic testing is the go-to choice for most projects. 

Whatever your needs, it is crucial to get the right equipment. Tiny damages to subsurface layers can unpeel into costly problems. Having the best testing equipment that is easy-to-use saves you time during testing, and saves you money during the lifespan of your manufactured equipment.

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