Several Factors Affecting the Measurement of Coating Thickness Gauges
The magnetic method for measuring thickness is affected by changes in the properties of the base metal (in practical applications, changes in the magnetic properties of low carbon steel can be considered slight). In order to avoid the influence of heat treatment and cold processing factors, standard plates with the same properties as the base metal of the specimen should be used to calibrate the instrument; The conductivity of the base metal has an impact on the measurement, and the conductivity of the base metal is related to its material composition and heat treatment method. Use standard plates with the same properties as the base metal of the specimen to calibrate the instrument; Every instrument has a critical thickness, beyond which the measurement is not affected by the thickness of the base metal; It is sensitive to the steep changes in the surface shape of the specimen, so measuring near the edge or inner corner of the specimen is unreliable; The curvature of the specimen has an impact on the measurement, and it increases significantly with the decrease of curvature radius. Therefore, measuring on the surface of bent specimens is also unreliable; The probe will cause deformation of the soft coating specimens, so reliable data cannot be measured on these specimens; The surface roughness of the base metal and coating has an impact on the measurement. The increase in roughness leads to an increase in impact, and rough surfaces can cause systematic and accidental errors. Therefore, the number of measurements should be increased at different positions during each measurement to overcome this accidental error. If the base metal on the substrate is rough, it is necessary to take several positions on the uncoated base metal specimen with similar roughness to calibrate the zero point of the instrument, or dissolve and remove the coating with a solution that does not corrode the base metal, and then calibrate the zero point of the instrument; The strong magnetic field generated by various electrical equipment around can seriously interfere with magnetic thickness measurement work; The adhesive substances that hinder the close contact between the probe and the coating surface must be maintained at a constant pressure during measurement, and the probe must be kept perpendicular to the surface of the specimen in order to achieve measurement.
