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​What Are The Influencing Factors Of The Coating Thickness Gauge
Oct 10, 2018

What are the influencing factors of the coating thickness gauge

The coating thickness gauge can non-destructively measure the thickness of non-magnetic coatings on magnetic metal substrates (such as steel, iron, alloys and hard magnetic steel) (such as aluminum, chromium, copper, tantalum, rubber, paint, etc.) and non-magnetic The thickness of a non-conductive coating on a metal substrate (such as copper, aluminum, zinc, tin, etc.) (eg, tantalum, rubber, paint, plastic, etc.).

What are the influencing factors of the coating thickness gauge, as follows:

1. Base metal magnetic properties

The magnetic thickness measurement is affected by the magnetic properties of the base metal (in practical applications, the change in the magnetic properties of the low carbon steel can be considered to be slight). In order to avoid the influence of heat treatment and cold working factors, the same properties as the base metal of the test piece should be used. The standard piece calibrates the instrument; it can also be calibrated with the test piece to be coated.

2. Matrix metal electrical properties

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

3. Base metal thickness

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. The critical thickness values of this instrument are shown in Table 1.

4. Edge effect

This instrument is sensitive to the steepness of the surface shape of the test piece. Therefore, it is unreliable to measure near the edge of the test piece or at the inner corner.

5. Curvature

The curvature of the specimen has an effect on the measurement. This effect always increases significantly as the radius of curvature decreases. Therefore, measurement on the surface of the curved test piece is not reliable.

6. Deformation of the test piece

The probes deform the soft cover specimens, so reliable data is measured on these specimens.

7. Surface roughness

The surface roughness of the base metal and the cover layer has an effect on the measurement. The roughness is increased and the influence is increased. Rough surfaces can cause systematic and accidental errors, and the number of measurements should be increased at different locations for each measurement to overcome this accidental error. If the base metal is rough, it is necessary to check the zero point of the instrument on the base metal test piece with similar uncoated roughness. Or dissolve the cover layer with a solution that does not corrode the base metal, and then proofread the instrument. Zero point.

8. Magnetic field

The strong magnetic field generated by various electrical equipment around it will seriously interfere with the magnetic method of thickness measurement.

9. Attached substances

The instrument is sensitive to adhering substances that prevent the probe from coming into close contact with the surface of the cover. Therefore, the attached material must be removed to ensure direct contact between the instrument probe and the surface of the test piece.

10. Probe pressure

The amount of pressure applied by the probe on the test piece affects the measured reading, so keep the pressure constant.