Dry-film thickness measurement: magnetic and mechanical methods

In the Coating industry, accurate measurement of dry-film thickness is crucial because it involves quality control and performance evaluation of coatings. Measuring methods for dry-film thickness are varied, including magnetic method, mechanical method and Microscope method. This article will focus on two main dry-film thickness Measuring methods, magnetic method and mechanical method.

1. Magnetic method

The magnetic method is a kind of Measuring method for non-Destructiveness instruments. According to the different substrates to be measured, it can be divided into magnetic Thickness Gauges and nonmagnetic Thickness Gauges, which are suitable for coating dry-film thickness measurement on magnetic metal substrates and nonmagnetic metal substrates, respectively. This is one of the main methods for dry-film thickness measurement at present.

Magnetic Thickness Gauges use the principle of electromagnetic field magnetoresistance to measure the coating thickness by measuring the Magnetic flux in the steel substrate, that is, the change in the gap between the magnet and the magnetic substrate. Another magnetic Thickness Gauge uses the principle of magnetic attraction method to measure coating thickness by overcoming the force required for the magnetic attractive force between the permanent magnet and the magnetic substrate. Nonmagnetic Thickness Gauges use the principle of eddy current thickness measurement to measure the thickness of the coating on the non-magnetic baseplate by inducing the size of the eddy current to change with the coating thickness on the instrument probe coil and the metal substrate.

2. Instruments and materials

The following instruments and materials are required for dry-film thickness measurement:

Thickness Gauge: Accuracy is 2μm, there are desktop and portable, and the specifications are graduated disc and digital display.

Calibrated standard sheet: used for calibrating Thickness Gauges.

3. Determination method

(1) Graduation disc Thickness Gauge

Manually place the probe on the coating under test, slowly push the instrument dial with your finger, and stop pushing when you hear a "click" sound. The reading indicated by the pointer is the dry-film thickness of the coating.

For automatic measurement, push the dial to the maximum range, press the button, and the instrument will automatically perform measurement.

(2) Digital magnetic Thickness Gauge

On a reference surface similar in nature to the substrate under test, carefully adjust the probe to zero and then calibrate using the standard sheet included with the instrument.

During measurement, the probe is placed on the coating to be tested, and the measurement is carried out at a distance of not less than 1 cm from the edge at the upper, middle and lower positions, and the coating thickness value is recorded.

4. Presentation of results

Take the arithmetic average of the measurement results of each point as the average dry-film thickness of the coating.

5. Reference standard

When performing dry-film thickness measurement, you can refer to the national standard GB/T 13452.2 "Determination of Paints and varnishes Paint Film Thickness".

Accurate measurement of dry-film thickness is crucial for the Coatings industry, ensuring the mass and performance of coatings. Measuring methods can be applied to different types of substrates and coatings, and choosing the right method is crucial for product quality control. Whether magnetic or mechanical, reliable dry-film thickness measurement solutions are provided, helping manufacturers ensure that their Coatings meet specifications and have the required performance.