Several Factors Affecting the Measurement of Coating Thickness Gauge

Each thickness measurement instrument has a critical thickness. Above this thickness, the measurement is not affected by the thickness of the base metal; it is sensitive to sudden changes in the shape of the surface of the test piece, so measurements at or near the edge of the test piece are not reliable. The curvature of the test piece has an influence on the measurement, and as the radius of curvature decreases significantly, therefore, the measurement on the surface of the curved test piece is also unreliable;

The surface roughness of the base metal and coating has an effect on the measurement. Roughness increases, the influence increases, the rough surface will cause system error and accidental error. In each measurement, the number of measurements should be increased in different positions to overcome this accidental error. If the matrix metal on the substrate is rough, the zero point of the instrument must be calibrated at several locations on the uncoated substrate sample with similar roughness, or the coating must be dissolved after removing the coating with a solution that is not corrosive to the substrate metal. Zero point

The strong magnetic field generated by various electrical equipment around will seriously interfere with magnetic thickness measurement;

The probe deforms the soft-coating test pieces, so reliable data cannot be measured on these test pieces;

Adhesives that interfere with the probe's close contact with the surface of the coating must be removed. During the measurement, the pressure must be kept constant and the probe should be kept perpendicular to the surface of the test specimen in order to achieve accurate measurements.

The magnetic method measures the thickness affected by the metallic change of the substrate (in practical applications, the change in magnetic properties of mild steel can be considered minor). To avoid the effects of heat treatment and cold working, the same properties as the base metal of the specimen should be used. Standard tablets calibrate the instrument;

The conductivity of the base metal has an influence on the measurement, while the conductivity of the base metal is related to its material composition and heat treatment method. The instrument should be calibrated using a standard sheet that has the same properties as the base metal of the test piece.