What is a Coating Thickness Gauge?

May 2, 2022
By Moshin Ali

A coating thickness gauge is a tool for determining the dimensions of the thickness of a dry layer, coating, corrosion, or any additional secondary layer deposited on a surface of the metal.

Coating thickness gauges are used to guarantee that corrosion protection material layers are applied efficiently and at a low cost. They aid in determining the insulating layer's predicted longevity, reliability, sturdiness, and functionality.

A coating thickness gauge is often used to determine the thickness of a dry film deposit. Dry film depth is perhaps the most critical parameter in this business due to its significance in the thin film application, performance, and budget.

Assessments of parched film thickness could assess a coating's predicted lifetime, guarantee the product's appearance & functionality, and assure conformity with various international regulations and requirements.

The thickness of the coating film represents a crucial variable that affects product quality, operational efficiency, and price transparency. Many different tools can be used to evaluate film thickness.

Each coating operation benefits from knowing what instrumentation is accessible regarding film thickness measuring and where to employ it.

The coverings, surface substances, coating depth spectrums, size and shape of items, and the expenditure of the gear all play a role in determining which approach is ideal for a particular coating evaluation or procedure.

Non-destructive parched film techniques such as eddy current inspection, magnetic inspection, ultrasonic inspection, or destructive dried film procedures are commonly used for hardened organic films.

GGC (Global Gauge Corporation or Global Gauge) was created in 1999 and purchased Measuray's resources. They launched the inaugural PLC-based instrument called Perfecta X-Ray Thickness Gauges shortly after.

Global Gauge has been running up against some of the industry's most established competitors throughout the years, such as PDM Technologies and ESC Opportunities. Global Gauge has expanded its equipment portfolio and has supplied hundreds of thousands of new and upgraded gauges.

Global Gauge equipment collection is now widely acknowledged as the professional benchmark for non-contact width, depth, and thickness assessment technologies in rolling plants and processing units.

At Global Gauge, users are provided with the best coating thickness gauges that are very accurate and yield precise measurements.

Gauges for measuring the thickness of coatings

In some circumstances, such as when a covering, paint, or varnish has applied to a steel substrate, it is crucial to quantify the thickness of actual material that has been adhered to another parent material.

Material thickness sensors will not serve in these situations since only one aspect of the covering or pigment is visible. Also, a material thickness scale like the one mentioned before would not be capable of obtaining a precise set of measurements.

Coating thickness instruments or gauges are used to determine the depth of a coating to ensure that it meets the appropriate criteria.

Coating thickness gauges are divided into two categories. The first is the destructive measurement type in which the instrument penetrates the dried covering down towards the foundation, which effectively determines the coating depth.

Wet covering gauges are likewise available, which choose the depth of a surface until it has hardened. The obvious flaw with this procedure is that it necessitates compromising the coating's quality to obtain a great reading.

The second category of covering thickness gauges determine coating thicknesses using only a non-destructive method. These thickness sensors can be made using technology such as x-ray technologies.

X-Ray thickness sensors are a type of methodology used to make a reliable coating weight gauge. A beam of x-ray radiation is emitted through the coating by a particular instrument called an integrated measurement head.

A fluorescence arises when x-rays strike a material interface. In this situation, the demarcation line across the bottom of our coating and the particular surface delivers a fluorescence that returns to the sensor.

This same coating weight gauge determines the thickness of a specific layer or varnish by analyzing the absorption that occurs in the rebound signal to be recorded.

Metals, polymers, composites, fiberglass, and ceramics are just a handful of the materials able to be used and inspected during this process.

This method primarily serves as a gateway to one surface of the workpiece, which makes it perfect for online processes where line speeds are high and access is limited. Coating thickness gauges have several advantages, which are:

  • Non-destructive inspection
  • Versatile and abundant measurement options
  • Quick Results
  • User friendly

What Is Powder Coating and What Does It Mean?

Powder coating refers to a type of coating that can be applied either in a dry powdered form. It differs from typical liquid paint enough that it necessitates using a solvent to allow the filler and binder components to coalesce in a suspended liquid.

This can be applied to items and materials such as aluminum tubing, domestic appliances, cycle and vehicle parts, drum gear, and more.

Powder coating can be applied electrostatically and cured by means of applying heat to create a thin layer of a cured coating. Powder coatings have been divided into two categories: thermoplastics and thermosets. A short sequence of bonds called a crosslinker is used in the thermosetting process.

It combines with the reactive chemical groups inside the powder, causing polymerization when baked. This improves the characteristics and performance of the coating material. The thermoplastic kind does not require any additional steps during baking; it just melts into the finished covering.

The following acrylics are the most common polymeric materials used throughout powder coatings:

  • Polyurethane
  • Polyester
  • Epoxy (fusion-bonded, hybrid, polyester)

Process of Coating 

Electrostatic Display Deposition (ESD) is widely used to obtain the best performance. This process utilizes a spray cannon to apply powder coating onto a metallic surface by releasing electrostatic charges upon the powder coating granules, subsequently driven towards the grounded area.

Following the surface treatments such as powder coatings, the material being treated with coating gets placed inside a curing furnace, where the layer interacts chemically to form long molecular chains, resulting in increased cross-linked concentration.

These anti-corrosive molecular copolymer chains are the most used method for applying powder coatings and treatments. Using this method, powder coatings could also be deposited into non-surfaces, including fiberboard and plastic.

Paint coating gauges and depth meters are crucial in certain industries such as automotive quality assurance, laboratory analysis, paint assessment, manual labor, second-hand car marketplaces, and corporate lacquering.  All these areas may require measuring coating density.

Choosing the Most Appropriate Coating Thickness Gauge

Filtering through your selections is, in some respects, the most challenging part of choosing the proper gauge. Fortunately, there have been a few simple methods for swiftly narrowing down your options. Consider the following four essential aspects to keep your hunt on track:

  • Material Assistance

Since not every coating thickness gauge may provide identical results, it's critical to consider temporal stability. How about chrome, for example? Aluminum? Is it made of enamel or rubber? What about magnetized materials such as iron and steel?

  • Instrument Accuracy 

Most applications can be satisfied with the rough accuracy provided by entry-level machinery. Elevated levels of precision such as in industrial line-based applications may be required for industrial or commercial operations.

  • User-Friendliness

The usage of coating gauges and thickness gauges may not always be straightforward. Consider whether the interface is user-friendly. Is it possible to read the demonstration? This is also a good idea to consider how frequently the equipment would be utilized by somebody unfamiliar with it.

  • Input of data

All right, you've gathered your data. What could you accomplish immediately with the information? Do you need to record the numbers on a notepad or manually enter them into Spreadsheets? The coating gauges and thickness gauges may come with accompanying software that allows users to load or transfer information to a computer.

Digital Coating Thickness Gauges

Digital coating thickness instruments are engineered to offer highly precise, dependable, and consistent coating thickness readings on most ferrous and non-ferrous surfaces.

This digital coating gauge or thickness instrument can measure dry film depth and thickness on magnetic metallic surfaces and non-magnetic metallic materials like lightweight materials such as Aluminum.

With non-magnetic coatings over magnetic surfaces like steel, the process of electromagnetic induction is utilized. The eddy current approach is applied regarding non-conductive coverings on non-ferrous metallic surfaces.

Gauges for Measuring Coating Thickness

Magnetic inducement equipment, electromagnetic devices, eddy current depth gauges, and x-ray-based gauges are four more devices that can be employed to detect coating weight. The first two of these enlisted procedures work by detecting changes in the electromagnetic influx intensity at the outer edge of such a magnetic sensor as it approaches a covered surface.

The influx density readings measured could be utilized to assess the coating depth on the surface.

The eddy current thickness sensor measures the thickness of non-conductive coverings on non-ferrous metallic surfaces. These machines produce an oscillating magnetic field by generating an elevated frequency switching current.

The oscillating magnetic field causes eddy currents along with the interface as it strikes the top surface, forming an antagonistic magnetic field. This same eddy current depth gauge may identify the oppositional area and determine the penetration depth of the coating.

Lastly, x-ray-based gauges are the best solution for industrial environments for applications like galvanizing, aluminizing, or tin-plating. The fluorescence generated by the x-rays on the substrate is reflected back to the sensors and the absorption of the material is measured to determine a highly accurate coating weight. 


To ensure that the instrument readings deliver and retain accurate values, particular material thickness indicators and the coating thickness gauges must be calibrated against standard sample tested specimens.

The absorption rate of of x-ray fluorescence in x-ray-based coating thickness gauges, for instance, is determined by the substance through which it travels. The the level of absorption for various material types should be recorded.

This data must be saved and utilized to calculate the proper absorption rate (and hence the thickness of the tested material). Gauges for coating thickness are standardized against recognized thickness criteria.

Thickness standards can come from various places, but it's better if they can be traced back to a national measurement organization like the National Institute of Standards and Technology (NIST).

It is crucial to make sure the benchmarks are several times as precise as the instrument they will be calibrating. Regular checks to these requirements ensure that the gauge is still in good working order.

When readings fall short of the gauge's precision specifications, they must be corrected or repaired before being calibrated.

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