Winterthur Instruments AG CoatMaster, Manual

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Operation Manual CoatMaster
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5 Measuring the coating thickness
5.1 Measuring principle
The CoatMaster operates according to the principle of thermal testing of coatings. Thereby the coat-­‐
ing surface is heated up by means of an excitation source, to draw conclusions about the coating
properties. A light impulse is used for excitation. After a short heat-­‐up by a few degrees the surface
cools down by transferring the heat in deeper areas of the coating and the substrate. The course of
the surface cooling depends on the physical properties of the surface and the properties. The thinner
the coating is (given that it has a lower thermal conductivity than the substrate), the faster the sur-­‐
face temperature decreases. A poor adhesion of the coating leads to a delayed cooling, as a strong
temperature gradient is formed at the boundary, which results in an excessive temperature within
the coating. The temperature behaviour over time provides information about the thickness, adhe-­‐
sion and material properties of the coating.
Figure 9:
Schematic diagram of the measuring principle
5.2 Measuring powder coatings before curing
Usually coatings are not even but show a waviness. The properties of this waviness are influenced by
different parameters like pretreatment, type and waviness of the substrate, paint type (e.g. grain size
distribution and chemical composition) as well as by the concrete conditions (temperature distribu-­‐
tion, curing times) during curing. Figure 3 shows a 3D microscopic record of this waviness.