In the field of coating, the measurement of dry film thickness is a crucial task. Accurate measurement of dry film thickness plays an integral role in the performance evaluation of coatings, acceptance of construction quality, and overall control of coating projects. This article will delve into the significance of dry film thickness measurement, the importance of measuring instruments and calibration.
Significance of Dry Film Thickness Measurement
The measurement of dry film thickness is a key indicator in coating engineering, which can directly reflect the protective performance of the coating film and the rationality of the coating process. When evaluating the performance of the coating, the dry film thickness is usually closely related to the corrosion resistance and durability of the coating film. In addition, the dry film thickness is also closely related to factors such as the appearance quality of the coating and the use efficiency of the coating material. Therefore, accurate measurement of dry film thickness is crucial to ensure the quality of the coating and prolong the life of the coating.
Measuring instruments and methods
The measurement of dry film thickness can be divided into two methods: destructive testing and non-destructive testing. Destructive testing requires damaging operations such as scratching the coating film, while non-destructive testing does not cause damage to the coating film. Typically, non-destructive testing methods are more commonly used, but destructive testing methods are more persuasive in the event of a dispute or arbitration.
1. Non-destructive measurement methods:
Micrometer
This is a common non-destructive measurement method suitable for thin film thickness. However, it has certain limitations in the measurement of complex curved or uneven surfaces.
Magnetic Thickness Gauge
It is suitable for anti-corrosion measurement on the surface of metal substrates, but it should be noted that magnetic Thickness Gauges are only suitable for magnetic metal substrates such as steel.
Eddy current Thickness Gauge
It is suitable for the measurement of anti-corrosion layer on the surface of metal substrates, especially for non-magnetic metal substrates such as aluminum and stainless steel.
2. Destructive measurement method:
Microscopy (ISO2808)
This method measures the thickness of the coating at the cut by cutting the coating film. Not only the total thickness of the coating film can be measured, but also the thickness of each layer in a multi-layer coating film. It is recommended as an arbitration method for coating film thickness.
Calibration of Thickness Gauges
Before measuring with a Thickness Gauge, it must be calibrated. No matter which Thickness Gauge is used, calibration is the key to ensuring the accuracy of the measurement data. Data without calibration is meaningless.
The way of calibration depends on the state of the surface. There is some controversy over whether to calibrate on a smooth surface on a steel surface after sandblasting. Some standards, such as ISO2808 (Third Edition) Method 10, stipulate that calibration is carried out on a smooth surface. However, in practice, the surface after sandblasting will affect the measurement result of the thickness of the coating film. Generally, when the thickness of the coating film is about 5 to 6 times that of the roughness, the effect of the roughness can be ignored.
To sum up, accurate measurement of dry film thickness is a key step in ensuring coating quality. Different measurement methods are suitable for different situations. Choosing the right measuring instrument and performing proper calibration can ensure coating quality, improve coating performance and prolong coating life.
