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Conductive vs Nonconductive Coating Thickness Measurement Inspection Tips

Coating thickness measurement is important in aviation maintenance

Both conductive and nonconductive coating thickness measurements require precision. Accurate coating measurements are crucial in the aerospace industry, as a loss of coating material compromises safety standards and can lead to dangerous malfunctions. Even a small amount of thickness lost can result in the degradation of assets over time until the situation becomes critical.

This is why nondestructive testing (NDT) is such a vital part of routine aircraft maintenance. Using the best possible NDT approach and equipment for a coating thickness measurement helps ensure no flaw goes undetected and allows analysts to provide early recommendations for repairs or replacements, preventing larger complications (which can cost significantly more to address) from developing. The following tips can further help analysts enhance and streamline the inspection process for the best possible results.

Tips for Conductive Coating Thickness Measurements

Since conductive coats can be applied in laminate, spray, or paint form, they are ideal for retrofitting or upgrading aircraft without replacing the material. Conductive coatings such as silver, copper, or molybdenum transmit heat and electricity as a safeguard against such dangers as lightning strikes or ice formation.

Any loss of coating thickness could negatively impact the integrity of the coating and expose substrate layers to a host of dangers. Ice formation is particularly perilous, as it can alter the aerodynamics of an aircraft and increase its weight to the point where it would be too heavy to safely operate. Additionally, a thin or damaged conductive coating can expose sub-layers to corrosion. Therefore, analysts need an instrument that can test variations in thickness while pinpointing areas of potential corrosion.

Tip #1: Choose Quality NDT Equipment

In order to detect thinning early on and prevent more dangerous complications from arising, analysts need precise instruments designed specifically to measure conductive coating thickness. Older or substandard instruments may cost less to acquire upfront than higher-quality alternatives. However, using inferior equipment can incur greater future costs down the road as it increases the risk of analysts overlooking certain difficult-to-detect flaws until they become more prominent problems requiring more expensive solutions.

Tip #2: Utilize a Modular Measuring System

The correct conductive measuring system depends on a variety of factors, such as the coating type and material type. But one commonly suggested method for conductive thickness coating is a modular measurement system (MMS). A modular system automates the measurements on conductivity and thickness, in addition to the substrate material. Further, MMS integrates various modules that permit flexible techniques. For example, there’s a module that can test the thickness of galvanized nickel coating on non-ferrous metallic material and another module for copper coating. Another module could use the magnetic-inductive and eddy-current measurement techniques for non-magnetic coating on such metals as copper or zinc.

Tip #3: Use Eddy Current Testing When Appropriate

Eddy current testing (ECT) can also be a useful approach to measuring conductive coating thickness—if the uppermost layer of coating is non-magnetic.

Ultimately, the optimal approach for inspecting the thickness of conductive coatings is best determined on a case-by-case basis. 

Tips for Nonconductive Coating Thickness Measurements

Nonconductive coatings protect components from excessive heat, electricity, and corrosion. If a layer of epoxy is applied to a steel sheet, for example, the nonconductive paint protects the steel subsurface from acidity or rusting. The thinner the coating becomes, the more exposed the component is—and the more likely it will be to sustain damage such as thermal fatigue or warping.

Tip #1: Use Eddy Current Testing for Nonconductive Materials

Eddy current testing is one of the best methods for measuring nonconductive coatings because it can test anodic coating, in addition to most nonconductive coatings on nonmagnetic basis metals. ECT instruments have features that streamline the inspection process and produce comprehensive data. Further, ECT instrumentation is more likely to produce fast, accurate results thanks to the enhanced technology and software. Modern-day ECT instruments and scanners with high signal-to-noise ratios (SNRs) tend to be more efficient and effective than other testing approaches that may require more intensive setup and cleanup or even cause damage to the coating (such as those methods that require analysts to scrape samples from the coating itself for testing).

Tip #2: Incorporate Surface-Array Probing

While even conventional eddy current testing tends to produce better-quality data than other methods, including surface-array probing can further enhance data quality and testing comprehensiveness. Surface-array probing can adapt to a non-flat surface while detecting thickness variations with impeccable precision. The best probes include high-quality coil sets that foster even greater accuracy and reliability.

Tip #3: Utilize Portable Instrumentation

For the greatest level of both efficiency and convenience, analysts should be equipped with portable ECT equipment. Handheld devices are on the cutting edge of the eddy current testing field, affording analysts increased mobility and ease of access to certain difficult-to-reach areas without sacrificing high SNRs. Quality eddy current array handheld instruments can reduce inspection times by up to 95 percent compared to traditional pencil probing.

Improving Coating Thickness Measurements

More and more people are taking to the skies—last year alone, airlines carried nearly 4.5 billion passengers to their destinations. This makes it more imperative than ever for aircraft inspections to be airtight. The more comprehensively components can be scanned, the safer all of those passengers (not to mention, crew members) will be.

Utilizing the best techniques and NDT solutions for each application, whether analysts are testing conductive or nonconductive coating thickness, is key to success. In all cases, high-quality instruments, scanners, and probes can help increase testing efficacy and minimize the possibility of overlooked thinning in coatings leading to greater-scale dilemmas down the runway.

Zetec has been a leading provider of quality nondestructive testing equipment for decades. Contact us today for more information about our eddy current and ultrasonic testing solutions.