In the detection of paint and coating film, coating film thickness is a very important control item content. In the process of coating film construction, due to the uneven thickness of the paint film after coating or the thickness not meeting the specified requirements, it will have a significant impact on the performance of the coating. This method is applicable to the determination of the thickness of the clear film. The measurement needs to be carried out immediately after the paint film is prepared, so as to avoid the shrinkage of the paint film due to the evaporation of the volatile solvent. At present, there are two kinds of wet Film Thickness Gauges commonly used, wheel gauge and comb gauge.
(1) Wheel gauge
1. Scope and description
This method is suitable for the measurement of wet film thickness on laboratory test panels or on freshly painted surfaces.
2. Instruments and Materials
Wheel gauge: It consists of three equally spaced wheels coaxially, the middle one is slightly smaller than the outer wheel, and is eccentric with a height difference. When the instrument rolls on the wet film, the thickness of the wet film can be read from the position where the edge of the middle wheel just touches the surface of the wet film, corresponding to the scale on the outer wheel.
3. Measurement method
(1) During the test, the wheel gauge should be placed vertically on the surface of the paint film, so that the maximum scale of the two outer wheels is in contact with the substrate, and the wheel gauge cannot shake from side to side, otherwise there will be errors in the measured value.
(2) Roll the wheel 180° along the surface and check where the middle rim first contacts the wet film surface. The calibrated scale will indicate the wet film thickness at this point.
Note: When the wheel gauge rolls on the coating surface, it is better to start from the place with the largest gap, so that the wet film is not pushed and squeezed, and the measured value is more accurate.
4. Result representation
Take at least two more readings in the same manner at different locations to obtain representative results in µm over the painted range.
5. Reference standard
National standard GB/T13451.2-1992.
(2) Combing rules
1. Scope and description
This method is suitable for the measurement of wet film thickness during on-site painting operations, and the measured value can roughly indicate the wet film thickness.
2. Instruments and Materials
Comb Gauge: It is made of metal or plastic thin plate, and the periphery is composed of comb teeth. The outer teeth at both ends are on the same horizontal plane, forming a baseline, and the middle inner teeth have different gaps from the horizontal plane. Layer thickness value.
3. Measurement method
During the test, press the comb gauge vertically and firmly on the surface of the coating film to be tested, some of the teeth are wetted, remove the comb gauge, check the tooth gap, determine the shortest tooth that is in contact with the wet film surface, and finally touch the wet film. The value between the film tooth and the first scale shown that does not touch the wet film tooth is recorded as the diffuse film thickness.
4. Result representation
The reading between the last tooth that was wetted and the tooth that was not wetted is the thickness of the measured wet paint film, expressed in m. Take at least two additional readings in different locations in the same manner to obtain representative results for the painted area.
5 reference standard
National standard GB/T13451.2-1992.
