What factors affect the measurement of coating thickness gauge?
1. Magnetic properties of matrix metal
Magnetic thickness measurement is affected by the magnetic change of the base metal (in practical application, the magnetic change of low carbon steel can be considered as slight). In order to avoid the influence of heat treatment and cold working, the instrument should be calibrated by using a standard sheet with the same properties as the base metal of the specimen. The test piece to be coated can also be used for calibration.
2. Electrical properties of matrix metal
The conductivity of matrix metal has an influence on the measurement, and the conductivity of matrix metal is related to its material composition and heat treatment method. Calibrate the instrument with a standard sheet with the same properties as the base metal of the test piece.
3. Thickness of base metal
Each instrument has a critical thickness of the base metal. Above this thickness, the measurement is not affected by the thickness of the base metal.
4. Edge effect
This instrument is sensitive to the abrupt change of the surface shape of the specimen. Therefore, it is not reliable to measure near the edge or inner corner of the specimen.
Step 5 Curvature
The curvature of the specimen has an influence on the measurement. This effect always increases obviously with the decrease of curvature radius. Therefore, it is unreliable to measure on the surface of a bent specimen.
6. Deformation of specimen
The probe will deform the soft cover specimens, so reliable data cannot be measured on these specimens.
7. Surface roughness
The roughness of the surface of the base metal and the coating has an influence on the measurement. As the roughness increases, the influence increases. Rough surface will cause systematic error and accidental error, and the number of measurements should be increased at different positions every time to overcome this accidental error. If the base metal is rough, it is necessary to take several positions on the uncoated base metal specimen with similar roughness to check the zero point of the instrument; Or use a solution that is not corrosive to the base metal to dissolve and remove the covering layer, and then calibrate the zero point of the instrument.
8. Magnetic field
The strong magnetic field generated by various electrical equipment around will seriously interfere with the magnetic thickness measurement.
9. Attached substances
The instrument is sensitive to the attached substances that prevent the probe from contacting closely with the surface of the coating. Therefore, the attached substances must be removed to ensure the direct contact between the probe of the instrument and the surface of the tested part.
10. Probe pressure and lateral head orientation
The pressure exerted by the probe on the specimen will affect the measured reading, so keep the pressure constant. The placement of the probe has an influence on the measurement. During measurement, the probe should be kept perpendicular to the surface of the sample.
