Skygauge Robotics' new dry film thickness (DFT) probe attachment lets you measure coating thickness remotely with the same precision as the human hand. Skygauge enables you to complete SSPC-PA 2 compliant inspections faster, safer, and easier than conventional methods. In this article, we take a deep dive into DFT, the surrounding standards, and the advantages of Skygauge as an emerging technology in this space.

What is DFT

Dry Film Thickness (DFT) testing involves measuring the coating thickness of paint, or another coating material, on top of a metal substrate. This can be paint on the wall of a storage tank, or the side of a ship, for example.

Paint thickness measurement is not just about maintaining a pretty coat of paint. The coating layer protects the underlying asset from moisture and rust.

DFT Standards

DFT Inspections help protect large painted industrial assets, such as these storage tanks, from corrosion

The most common standard for Dry Film Thickness testing is SSPC-PA 2. This standard outlines procedures for non-destructive measurement of coating thickness.

According to this standard, an inspector must take 5 sample points for every 10m2 area of painted surface. Each sample point should be a randomly selected 4cm circle, and the inspector must complete 3 DFT readings within each point.

Inspectors take readings with a commercially available Dry Thickness Film gauge, such as the ERAY Mil Thickness Gauge used onboard the Skygauge.

Each 10m2 area therefore requires 15 readings (3 readings in 5 areas).

To pass the inspection, the average thickness across these five sample areas should be between 9-12mils (0.2286-0.3408mm). If the average thickness is below this range, the coating in this 10m2 area is thinning, and in need of an additional coat of paint. An area where the reading is too high needs to be sanded down.

There is a caveat in the SSPC-PA 2 - if the coated area is particularly large, the inspector does not have to measure each 10m2 area. If the area is between 30m2 to 100m2, 3 arbitrarily selected, non-overlapping 10m2 areas must be inspected. If the area is larger than 100m2, inspectors must repeat this process of scanning 3 random 10m2 areas in each 100m2 area.

The Current Process

Considering the process outlined above, let's consider the example of a cylindrical tank 35m (117ft) high with a 44m (146 ft) diameter base. The surface area of the side of such a cylinder 138x35 meters, or 4830m2.

An inspector would have to inspect forty-eight 100m2 areas, and one 30m2 area. In each area, they would conduct a total of 45 readings (15 readings, in three randomly selected areas). That is a total of 2205 readings to map the entire tank surface.

The traditional method for conducting these inspections involves sending up an inspector to physically make contact with each of these 2205 points by hand. The inspector would use a rope hoist, scaffolding, or a man-lift to reach the target site. They would then press a handheld DFT sensor to each inspection point to collect inspection data.

DFT with Skygauge

Skygauge uses a modified handheld DFT gauge, with no loss of accuracy compared to manual testing.

Compared to traditional methods, an aerial data-gathering approach is faster, cheaper, and safer. The Skygauge DFT can take 60 coating thickness measurements per hour, easily completing a 360-point inspection in a single day, including setup and teardown. This results in a 90%+ reduction in inspection time over conventional approaches.

With Skygauge the drone pilot remains safe on the ground when conducting the test. With conventional methods, an inspector needs to risk life and limb on ropes, cranes, or scaffolding, working at height. Considering that falls from a height are the second most common source of workplace injuries, any technology that helps reduce work at height is a lifesaver.

The Skygauge uses a modified version of the same gauge used for hand-held testing, and has the same precision as the human hand.

What does this mean for your business?

If you are a drone services provider, looking to expand into physical work, the Skygauge DFT is yet another tool that you can use to market more services to your customers. Few if any drone service providers currently offer physical inspection work, and even fewer can offer DFT.

Read our article on how Skygauge can help you win more customers for your drone services business for a more in-depth look at the economic benefits of Skygauge.

The Skygauge's DFT gauge is interchangeable with the regular ultrasonic spot thickness gauge, and both can be mounted on the standard Skygauge body. If you already own a Skygauge, it is simple matter of purchasing the DFT upgrade, and your drone will now be able to conduct both DFT and spot thickness UT in the field.

The Skygauge DFT also pairs well with upcoming attachments, such as our paint touch-up tool.

As an inspector or drone service provider, arming your Skygauge with DFT means you can offer more services, and a more comprehensive inspection suite to both new and existing customers.


Dry Film Thickness is a common inspection type, governed under the SSPC-PA2 Standard. This standard governs how to properly gauge the thickness of paint coatings on industrial assets. Thinning paint is not just an aesthetic concern - it can lead to rust and eventual failure of the underlying asset. Therefore, DFT inspections are an important safety consideration.

Using the Skygauge lets you complete DFT inspections faster, cheaper, and safer than slow traditional methods like rope access or scaffolding. You can use this advantage to win more clients for your inspection business and remarket existing ones with new services.

Contact us today to learn more about what Skygauge can do for your industrial inspection business!