Non-contact
coating thickness measurement

In photothermal coating thickness measurement, a light source gently heats the surface. The heat spreads through the coating towards the substrate, is reflected at the interface and returns to the surface, where it can be detected in the form of thermal radiation. The coating thickness can be determined from the precise measurement of the transit time of the heat through the coating.

Further details can be found in our White Paper.

Measuring devices based on induction or eddy currents require a ferromagnetic or conductive substrate. In the case of a micrograph, the component must be destroyed. Photothermal measuring devices work differently: They irradiate the coating with light and measure the development of the resulting thermal radiation over time. This makes the measurement possible from a distance in a contactless and non-destructive manner.

The photothermal measuring principle works for almost all combinations of coating and substrate. Our validated applications include wet and powder paints, primers, corrosion protection and functional layers such as adhesives on metal, plastic, ceramics, glass, wood and other materials.

Feel free to browse our list of all validated applications. Didn’t find what you were looking for? Contact us!

First, the surface of the coating is heated with a light source. For this to happen, the coating must absorb the light well. Black, matt and opaque paints absorb near-infrared light very well. White or transparent paints, on the other hand, can often be measured better with UV light. We determine the appropriate light color (wavelength) as part of the preliminary examination.
If the surface is heated, the heat must be reflected at the transition between the coating and the substrate. This requires a thermal contrast between the coating and the substrate; the coating must be made of a different material than the substrate.

Further details on all of the requirements mentioned and their influence can be found in our White Paper.

A major advantage of photothermal coating thickness measurement is that it works contactless. This means that the measurement can be performed immediately after coating, before curing. This enables inline quality control in which corrections are still possible without waiting for the energy-intensive curing process and possibly producing rejects.

Our photothermal measurement technology is designed for measuring a single layer thickness or the total thickness of several layers. A measurement, for example, of a base coat with a known E-coat thickness is possible without any problems. In terms of rapid process monitoring and control, step-by-step measurement can even be useful. In certain constellations, for example if the thermal properties of the coatings are sufficiently different, the system can also resolve individual thicknesses within a multi-layer system.

We would be happy to check whether your specific system is measurable as part of a preliminary analysis. Contact us today!

Our all-round measuring device is the CoatPro, a photothermal device that can measure the thickness of almost any coating on any substrate. It combines long-lasting LED technology with a highly sensitive sensor and a specially developed lock-in amplifier to achieve highest precision even with short measurement times. This makes it ideal for rapid inline measurements as well as for laboratory analysis.

Recently, we have developed the CoatPro XD to rapidly record complete coating thickness distributions, even on large components. This measuring system is based on a modular camera system and enables the measurement of the entire thickness distributions on a component within a few seconds. It is optimized for thick coatings (>50 µm), such as powder layers or flame retardant layers.

Are you unsure which measurement system is the best choice for your situation? Contact us today for our expert opinion.

CoatPro and CoatPro XD work with periodic excitation. The constant frequency of this excitation allows very low-noise filtering of the actual measurement signal. Hence, both devices can precisely measure those coating systems that are difficult to measure for other photothermal measuring devices (e.g. clear coat, thin metal layers). The advanced optical design also ensures high tolerance for complex component geometries, curved surfaces and variable working distances. Finally, both devices use of long-lasting and efficient LED technology, which ensures low-maintenance operation at low costs and high safety.

Our measuring devices measure the time it takes for the heat to diffuse through the coating. The time required depends on the coating thickness, as heat takes more time to pass through thicker coatings, and on the thermal conductivity of the coating. The influence of this thermal conductivity is calculated out through calibration so that the measured time can be converted directly into the thickness. Calibration is carried out by our experienced application engineers individually for each coating when the measuring system is purchased. The included software also enables guided calibration of new coatings after mandatory training.

If you would like to find out more about the details of the calibration, contact us for a discussion.