Two Methods of Coated Film thickness measurement

When working on a project with a high performance coating, you need to consider how you will measure the coating thickness to ensure it is within specification. The thickness of the coating is often the key to ensuring that the coating will perform as it should when and when it is applied. Usually the thicker it is, the more protection it will provide to the substrate, but this is not always the case, and sometimes the coating is as bad as it was applied. Coating thickness can be important for water resistance, corrosion resistance, adhesion on rough surfaces, aesthetics, etc., but in most cases it is used with paint on steel. By monitoring and recording your coating thickness readings, you can be sure that you are getting a high-quality finish that will perform as intended and, as an added bonus, that you are not wasting material and money unnecessarily.

You can try two methods to test coating thickness:

Coating Thickness Gauge

Coating Thickness Gauges are used after the coating has been applied and cured, they use a probe that will give you a reading when it is brought close to the surface. Coating Thickness Gauges are commonly used in various stages of projects to check existing coatings on surfaces to ensure they are suitable for overpainting, to check progress throughout the project to ensure each coat is up to par, and finally at the end The project checks that all areas have received DFT (Dry Film Thickness) and they should meet specification. If you want a simple tool, we recommend the Coating Thickness Gauge (C5007). This meter is ideal for measuring all coatings on any metal substrate. A magnetic induction probe using the eddy current principle means you can check that a surface is coated with the correct coating thickness. This tool is one of the professional ones on the market, which means you can rest assured that you are making the right decisions with your paint.

Wet film measurement

Another way to measure coatings is to use wet film measurements. This method measures the thickness of a coating while it is still wet - WFT (Wet Film Thickness). We think the Tricomb Plastic Wet Film Gauge (W2008) is desirable because you can test wet film thickness quickly and cheaply, and even let them dry as a way to record coating thickness. These wet film gauges are disposable and have metric values ​​on the front of the meter and imperial values ​​on the back for measurement. The advantage of wet film gauges over dry Film Thickness Gauges is that they allow coaters of coatings to instantly adjust applications as needed to increase the thickness they apply or decrease the thickness they apply to the substrate to ensure correct Applications.

Once you decide which method to use to monitor your application, or indeed if you decide to use both, you need to make sure you understand the difference between wet film thickness and dry film thickness. Although the description makes them fairly self-explanatory, it can be easy to find wrong numbers from specs or data sheets when done in the field or under stress, especially when they are abbreviated WFT and DFT.

The wet film thickness figures given in the specification relate to the thickness of the coating which is still wet when just applied, once the coating starts the drying process, solvents and volatiles will leave the coating and its thickness will decrease, once cured it can be read dry film thickness. How much the thickness is reduced depends on the volume solids of the coating, the higher the volume solids of the product, the less stuff escapes from the coating and therefore the less the thickness is reduced. For example, if a coating is specified to be applied at 500 microns WFT (wet film thickness), and the product has a volume solids of 50%, once dry, the DFT (dry film thickness) reading will be 250 microns. Some coatings are 100% volume solids, which means no thickness is lost between WFT and DFT.

Finally, coatings are usually measured in microns (often expressed in μm). 1μm (micrometer) = 1/1000mm so when you get to 1000μm you have a coating thickness of 1mm. In the US, they tend to use Mil or Thou as their form of measurement, 1 Mil = 1/1000th of an inch. 1 Mil/Thou = 25.4 microns (μm).