Precautions for operating a coating thickness gauge
A coating thickness gauge is a non-destructive testing instrument specifically used to measure various paint film thicknesses. Many people find that the measured data has a large error during measurement. Why does this situation occur?
The same coating thickness gauge may result in significant differences in data measured by different individuals or on different types and states of substrates for the same coating. This is due to factors such as measurement personnel, substrate material, thickness, surface condition, and measurement position of the measured paint film. When using a coating thickness gauge, the following points should be noted when using the coating thickness gauge:
1. Before use, carefully read the instrument user manual
Instruments from different manufacturers and brands have different structures, buttons, calibration, and other aspects. Therefore, before use, it is necessary to carefully read the user manual of the instrument to avoid measurement data errors caused by misoperation.
2. Pay attention to the material of the metal substrate
The magnetism and conductivity of different metal matrix materials are not the same, which can affect the measurement results. The use of magnetic method for thickness measurement is affected by the magnetic changes in the base metal (in practical applications, the magnetic changes in low-carbon steel can be considered minor). In order to avoid the influence of heat treatment and cold working factors, the instrument should be calibrated using a standard piece with the same properties as the base metal of the test piece, or calibrated using the test piece to be coated. Due to the different compositions and heat treatment methods of the base metal, its electrical conductivity varies. Therefore, a standard piece with the same properties as the base metal of the tested specimen should be used to calibrate the instrument.
3. Pay attention to the shape of the test piece
In actual production, there are differences in the material thickness, shape, surface roughness, etc. of the workpiece, which can affect the actual measurement results. Each instrument has a critical thickness of the base metal. If the thickness is greater than this, the measurement is not affected by the thickness of the base metal. If the thickness of the specimen material is less than the critical thickness required by the instrument, the detection result will differ from the actual thickness. Some instruments are very sensitive to sharp changes in the surface shape of the specimen, so the values measured near the edge or inner corner of the specimen may be unreliable. In actual measurement, it is recommended to choose a location far away from the edge and inner corner. The surface of the specimen not only exhibits steep changes in shape, but may also have different curvatures. The measurement results of some instruments always increase significantly with the decrease of curvature radius. Therefore, even if the minimum curvature radius is taken into consideration when selecting instruments, measurements should still be made as much as possible in flat areas.
