Home   >   Blog

Coating Thickness Gauge: Definition and Working Principle

In this blog post, you’ll read:Coating thickness gauge can help determine if there have been repairs or rust on an automobile and it can work with three measurement methods.

Table of Contents

Have you ever wondered how a coating thickness gauge works? 

One of the most popular uses of a coating thickness gauge is typically for a buyer at a car auction, and it’s an essential tool because they are deployed to ascertain an automobile’s actual worth. 

The coating thickness gauge assists in determining if there’s been prior bodywork done on the car’s painting which may reduce its value, or if the automobile has been repainted to cover up a previous dent on the vehicle via an accident or by any other means.

We know you’d like to learn more about this tool, and that’s why we’ve put together this guide. So, if you are ready, let’s jump right in.



I. What is Coating Thickness Gauge?


Without wasting further time, a coating thickness gauge is a tool that evaluates the thickness of a coating obviously without any vandalism done to the coating. This process should be done habitually as the film’s density can affect the paint’s appearance, opacity, and protective attributes. This is why a consistent measurement is necessary.

Furthermore, a coating thickness gauge, also referred to as a paint meter, is necessary to observe and maintain the coating attributes during a painting process. Also, it helps to measure the dry film thickness. 

A coating thickness gauge is essential to monitor the amount of coating applied to avoid flaking, cracking, and a longer drying time.


What is Coating Thickness Gauge



II. Why is Coating Thickness Gauge So Important?


So, apart from helping to monitor the drying time or to avoid flaking, which is often unnoticed, especially during an automobile’s inspection, there is other importance of checking the car paint thickness:


  • To check for past accident damage:

Picture this. Imagine you’re at a dealership looking to buy a car that has been previously used. How do you thoroughly inspect such an automobile to avoid overpricing? 

Damage caused by accidents is one of the things to consider when buying a car, and this is a major issue many car sellers try to deflect from or cover up. Therefore, a coating thickness will uncover any discrepancies in the car’s paint thickness or coating, thereby allowing you the knowledge of whether the car has been repainted or resprayed.


  • To check for rust or rust repairs:

Like the first reason a coating thickness gauge is importantly mentioned above, checking for rust and repairs technically is also a significant thing to look out for when inspecting an automobile. To check for this disparity, the coating thickness gauge must be deployed to indicate where the thickness is different, or there’s no reading at all.

The coating thickness gauge can identify if there is a current rust problem or if there has been repairing and can be dangerous to the car.


  • To save you money:

A coating thickness gauge can save you money by identifying underlying problems a car has, and therefore, you don’t end up buying a pocket drainer. As mentioned earlier, rusts, accidents to the car, or repairs can cost you more when examination for coating thickness is not conducted. Rust issues especially can be the expiration of an automobile. So, why pay so much for scrap metal when you can altogether avoid it?


  • To show the owner or seller you are serious:

When dealing with car sellers, some vital information can be withheld from you, but when the seller understands you are ready for a thorough inspection of the car, critical information about the vehicle is divulged. In addition, with helpful information, there’s room for further bargaining between both parties.

In essence, no seller wants to be caught lying about problems associated with the car, and that can only be possible by showing up for inspection with the right tools, and a coating thickness gauge is one of them.


➤ Related Article: How to Check Car Paint Thickness with a Coating Thickness Gauge?


III. Features and Benefits of Coating Thickness Gauge


As with many inspection tools, the coating thickness gauge also has varying features which enable it to perform its functions optimally. We consider these features in detail below. 


  • When considering different types of coating thickness gauge, you’ll quickly find out that there is a wide range of accompanying probes deployed for inspection. The probe is the heart of any coating thickness gauge because it directly affects the accuracy of test results. The shape and surface of the test object determine the type of probe used with the coating thickness gauge.
  • There is also a wide range of coating thickness gauges for most tangible coating thickness measurements.
  • Preconfigured data assessment features are resent on most coating thickness gauges.
  • Many, if not all, coating thickness gauges are user-friendly with an intuitive, easy-to-navigate user interface.
  • Measurement results are automatically captured as soon as the coating thickness gauge is deployed.
  • Different industries require a coating thickness gauge for various use and purposes. This might range from robust, rugged, simple coating thickness gauges for protection tasks to coating thickness gauges for industrial use with all-inclusive statistical functions.



IV. How does Coating Thickness Gauge Work?


The working principle for a coating thickness gauge is in three forms which are listed and explained thus:


  • Magnetic Induction Principle:

This is used to measure the coating thickness on magnetic surfaces, and it’s a measurement that requires high precision. This principle is measured by the level of magnetic fluidity the probe sends through the non-magnetic coating, which also streams to the magnetic surface. The relationship between the coating thickness, the magnetic fluidity, and the resistance is observed in enumerating the coating thickness on the magnetic surface.

It is generally observed that the thicker the coating on the magnetic surface, the larger the magnetic resistance and the smaller the magnetic fluidity.

Using the magnetic induction measurement with coating thickness gauge requires that the permeability is at a specific level. The magnetic absorbency of the surface is above 500. The difference in absorbency between the surface and the coating should be large if the coating on the surface is also magnetic. 

The non-magnetic elements that enable this principle include paint, enamel, aluminum, brass, copper, chrome, etc.


  • Eddy-Current Principle:

The principle of eddy current evaluation is simply that a high-frequency AC charge produces an electromagnetic field in the probe coil. An eddy current is established when the probe is near a conductor (usually a metal). The magnitude of the eddy current has a proportional relationship with the interspace between the probe and the conductive surface.

The nearer the probe is to the conductive surface, the bigger the eddy current and the bigger the reflection resistance. When the probe is at a considerable distance from the conductive surface, the eddy current will be tinier, and the reflection impedance will also be tinier. 

Therefore, this quantity instantly indicates the dimensions between the probe and the conductive surface, which is the coating thickness.

This non-magnetic probe usually utilizes high-frequency materials such as the coil core. The massive distinction from the above measurement is that the probe is dissimilar, the signal frequency is also non-identical. The signal proportion and scale relationship are also distinct. 

The eddy current principle of coating thickness gauge measurements is typically employed on non-conductive surfaces, which include aircraft surfaces, aluminum alloy doors, plastic coatings, etc.


  • Ultrasonic Principle:


Working Principle of Coating Thickness Gauge


For the Ultrasonic measurement of coating thickness, this is enabled by transmitting an ultrasonic vibration through a coating with a probe and a couplant administered on the surface. A bottle of standard glycol gel is usually attached to the instrument. 

Otherwise, a drop of fluid can perform the function of a couplant on smooth exteriors. Then the probe is placed flat on the surface, and holding down starts the measurement. A double beep or a green light alert for completion when the measurement is done, and the screen displays the last measurement. Multiple measurements can be made at the same point by continuously holding down the probe on the surface. And finally, the probe must be cleaned with a soft cloth or tissue.





In a nutshell, coating thickness gauges help determine if there have been repairs or rusts on an automobile and are generally used by buyers to inspect the automobile’s framework. It is a tool that allows measuring coating thickness without any form of destruction to the coating.

Furthermore, coating thickness gauge is also important to determine past accident damage, rust or rust repairs done on the coating surface to hide intrinsic information, save money, etc.

Finally, coating thickness gauge working principles utilize three different measurement methods: the magnetic induction principle, eddy current principle, and ultrasonic principle.

4.8/5 - (60 votes)