Coating Thickness Measurement Gages

Image for Coating Thickness Instruments Overview video
Coating Thickness Instruments
Overview Video

Coating thickness or dry film thickness (DFT) is an important variable that plays a role in product quality, process control, and cost control. Measurement of film thickness can be accomplished by selecting the best mil gage for the particular application.

Why Dry Film Thickness Measurement is Important

Dry film thickness (DFT) or coating thickness is arguably the single most important measurement made during the application and inspection of protective coatings. Coatings are designed to perform their intended function when applied within the DFT range as specified by the manufacturer. Correct thickness ensures optimum product performance. Even the most basic specification will require DFT to be measured.

The Measure of Quality

Regular film thickness measurement helps control material costs, manage application efficiency, maintain finish quality, and ensure compliance with contract specifications. Paint manufacturers recommend target ranges to achieve optimum performance characteristics and clients expect these parameters to be met.

See below for more information about coating thickness measurement and gages.

All Metals
Product photo of the PosiTector 6000, coating thickness gauge for all metal substrates with cabled probe

Digital Coating Thickness Gages for ALL Metal Substrates

PosiTector 6000

Rugged, fully electronic coating thickness gages use magnetic and eddy current principles to measure coating thickness on both ferrous and non-ferrous metals, accurately and quickly.

Conforms to ISO 2178/2360/2808, ISO 19840, ASTM B244/B499/D1186/D1400/D7091/E376/G12, BS3900-C5, SSPC-PA2, US Navy NAVSEA PPI 63101-000, US Navy NAVSEA 009-32, AS 2331.1.4, AS3894.3-B and others.

Non-Metals
Product photo of the PosiTector 200, coating thickness gauge for non-metal substrates

Ultrasonic Coating Thickness Gages for Non-Metal Substrates

PosiTector 200

Non-destructively measures a wide variety of applications using proven ultrasound technology. Measure coating thickness over wood, concrete, plastic, and more. Advanced models measure up to 3 layers with graphics.

Conforms to ASTM D6132 and ISO 2808.

Uncured Powder
Product photo of the PosiTest PC, non-contact uncured powder thickness gauge

Non-contact Uncured Powder Thickness Gage

PosiTest PC

Affordably measures uncured powder coatings using non-contact ultrasonic technology to predict a cured thickness.

Conforms to ASTM D7378.

All Metals
Product photo of the PosiTest DFT, economical coating thickness gauge for all metal substrates

Economical Coating Thickness Gage for ALL Metal Substrates

PosiTest DFT

Measures coatings on metal substrates. It is the economical choice that retains the uncompromising quality of DeFelsko coating thickness and inspection instruments.

Conforms to ISO 2178/2360/2808, ISO 19840, ASTM B244/B499/D7091/E376, BS3900-C5, SSPC-PA2 and others.

Steel Only
Product photo of the PosiTest, mechanical magnetic coating thickness gauge for non-magnetic coatings on steel

Magnetic Coating Thickness Gage for Non-Magnetic Coatings on Steel

PosiTest

PosiTest magnetic pull-off thickness gage (banana gauge) for the non-destructive measurement of non-magnetic coatings (paint, enamel, galvanizing, metalizing, plating, etc.) on steel.

Conforms to ASTM D7091/B499, ISO 2808 and others.

Steel Only
Product photo of the PosiPen, pen-type magnetic coating thickness gauge for steel

Pen-type Magnetic Pull-Off Coating Thickness Gage

PosiPen

PosiPen has a very small, unique magnet which can be placed with pin-point accuracy on extremely small parts, and on peaks and valleys. Ideal for measuring non-magnetic coatings such as paint, enamel, plating, and hot-dip galvanizing on steel.

Conforms to ASTM D7091/B499, ISO 2808 and others.

Uncured Powder
Product photo of the DeFelsko Powder Comb for uncured powder thickness on all substrates

Uncured Powder Thickness on All Substrates

Powder Comb

Check powder thickness with Powder Comb before curing to help ensure correctly cured film thickness the first time through the line. Avoid stripping and re-coating which can cause problems with adhesion and coatings integrity.

Principles of Operation of Coating Thickness Gages

What are the types of Coating Thickness Gages available?

DeFelsko offers a variety of coating thickness instruments and probes for a wide range of applications including for measuring coatings on metals, non-metals (wood, concrete, plastic, composites), and for measuring uncured powder coating thickness.

Check out our selection of coating thickness gages below.

Coating Thickness Gages for All Metal Substrates

What are Magnetic Film Thickness Gages?

Magnetic film gages are used to nondestructively measure the thickness of a nonmagnetic coating on ferrous substrates. Most coatings on steel and iron are measured this way. Magnetic gages use one of two principles of operation: magnetic pull-off or magnetic/electromagnetic induction.

Magnetic Pull-off (Type 1 - Pull Off Coating Thickness Gages)

Magnetic pull-off gages use a permanent magnet, a calibrated spring, and a graduated scale. The attraction between the magnet and magnetic steel pulls the two together.

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Magnetic and Electromagnetic Induction (Type 2 - Electronic Coating Thickness Gages)

Magnetic induction instruments use a permanent magnet as the source of the magnetic field. A Hall-effect generator or magneto-resistor is used to sense the magnetic flux density at a pole of the magnet. Electromagnetic induction instruments use an alternating magnetic field. A soft, ferromagnetic rod wound with a coil of fine wire is used to produce a magnetic field. A second coil of wire is used to detect changes in magnetic flux.

These electronic instruments measure the change in magnetic flux density at the surface of a magnetic probe as it nears a steel surface. The magnitude of the flux density at the probe surface is directly related to the distance from the steel substrate. By measuring flux density the coating thickness can be determined.

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What are Eddy Current Film Thickness Gages? (Type 2 - Electronic Coating Thickness Gages)

Eddy current techniques are used to nondestructively measure the thickness of nonconductive coatings on nonferrous metal substrates. A coil of fine wire conducting a high-frequency alternating current (above 1 MHz) is used to set up an alternating magnetic field at the surfaceof the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will set up eddy currents on thesurface. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the eddycurrents. The eddy currents create their own opposing electromagnetic field that can be sensed by the exciting coil or asecond, adjacent coil.

For instruction manuals, application notes, and technical articles for coating thickness measurement gages for all metal substrates, please find the following links:

Coating Thickness Gages for Non-Metal Substrates

Product photo of the PosiTector 200, coating thickness gauge for non-metal substratesPosiTector 200

How do you measure coating thickness on non-metals?

The ultrasonic pulse-echo technique is used to measure the thickness of coatings on non-metal substrates (plastic, wood, concrete, and composites) without damaging the coating.

Ultrasonic coating thickness gages (e.g. PosiTector 200) emit a high frequency sound pulse that travels into the coating via a coupling gel and reflects from ANY surface that is different in density. Coating thickness readings are obtained by measuring the time taken for the ultrasonic signal to propagate from the probe to the coating/substrate interface and back. The travel time is divided by two and multiplied by the velocity of sound in the coating to obtain the thickness of the coating.

Illustration — The PosiTector 200 interprets the largest "echo" within the selected range as the coating/coating or coating/substrate echo.
The PosiTector 200 interprets the largest "echo" within the selected range as the coating/coating or coating/substrate echo.

For more information about the PosiTector 200 and coating thickness measurement on non-metal substrates:

Coating Thickness Gage for Uncured Powder Coating Thickness

Product photo of the PosiTest PC, non-contact uncured powder thickness gaugePosiTest PC Powder Checker Non-contact Uncured Powder Thickness Gage

How do you measure Powder Coating Thickness before and after curing?

Thickness measurements of powder can be taken before and after curing. Substrate type, thickness range, part shape, and economics determine the best method to be employed.

For uncured applied powders, height measurement can be performed with DeFelsko Powder Combs. This technique is destructive and may require recoating the part. Coating powders generally diminish in thickness during the curing process so these procedures require a reduction factor be determined to predict cured film thickness.

Non-contact ultrasonic instruments, such as the PosiTest PC Powder Checker also measure uncured powder, but do so without touching the surface. Instead of measuring powder height, they automatically display a predicted cured thickness result. Accurate measurement at the time of application: eliminates over usage, Improves quality, controls set-up, reduces rework & waste saving money.

For after-cure measurement, a variety of hand held instruments are available. These non-destructive instruments employ either magnetic, eddy current or ultrasonic principles depending on the substrate.

For more information about the PosiTest PC and powder coating thickness measurement:

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