Surface Coating Thickness Gauge
In addition to measuring coatings on magnetic metal substrates and non-magnetic substrates, coating thickness gauges can also measure metal plating thickness gauges. Therefore, coating thickness gauges are also commonly referred to as coating thickness gauges.
Coating Thickness Gauge
1. Coating thickness gauge generally has the following five types according to the measurement principle: 1. Magnetic thickness measurement method: it is suitable for measuring the thickness of the non-magnetic layer on the magnetic material. The magnetic material is generally: steel\iron\silver\nickel .This method has high measurement accuracy
2. Eddy current thickness measurement method: It is suitable for measuring the thickness of non-conductive layer on conductive metal. This method is less accurate than magnetic thickness measurement method.
3. Ultrasonic thickness measurement method: At present, there is no such method in China to measure the thickness of the coating. Some foreign manufacturers have such instruments, which are suitable for the measurement of the thickness of multi-layer coatings or the occasions where the above two methods cannot be measured. But generally expensive \ measurement accuracy is not high.
4. Electrolytic thickness measurement method: This method is different from the above three methods. It does not belong to non-destructive testing and needs to destroy the coating. The general accuracy is not high. It is more troublesome to measure than other types.
5. Radiation thickness measurement: This kind of instrument is very expensive (generally above 100,000 RMB), and is suitable for some special occasions. The first and second methods are the most commonly used in China at present.
Principle of Conventional Coating Thickness Gauge
The covering layer formed to protect and decorate the surface of materials, such as coating, plating, cladding, sticking, chemically formed film, etc., is called coating in relevant national and international standards.
Coating thickness measurement has become an important part of quality inspection in processing industry and surface engineering, and it is an essential means for products to meet high quality standards. In order to make the products internationalized, there are clear requirements for the thickness of the cladding in my country's export commodities and foreign-related projects.
The measurement methods of coating thickness mainly include: wedge cutting method, optical section method, electrolysis method, thickness difference measurement method, weighing method, X-ray fluorescence method, β-ray backscattering method, capacitance method, magnetic measurement method and eddy current measurement law etc. Among these methods, the first five are destructive testing, the measurement methods are cumbersome and slow, and most of them are suitable for sampling inspection.
X-ray and β-ray methods are non-contact and non-destructive measurements, but the devices are complicated and expensive, and the measurement range is small. Due to the radioactive source, users must comply with radiation protection regulations. X-ray method can measure extremely thin coating, double coating and alloy coating. The β-ray method is suitable for the measurement of the coating and the coating with the atomic number of the substrate greater than 3. The capacitance method is only used when measuring the thickness of the insulating coating of a thin conductor.
With the advancement of technology, especially after the introduction of microcomputer technology in recent years, the thickness gauge using magnetic method and eddy current method has taken a step forward in the direction of miniature, intelligent, multi-functional, high-precision and practical. The measurement resolution has reached 0.1 microns, and the accuracy can reach 1%, which has been greatly improved. It has wide application range, wide measuring range, easy operation and low price, and is the most widely used thickness measuring instrument in industry and scientific research.
The non-destructive method neither damages the coating nor the base material, and the detection speed is fast, so that a large amount of detection work can be carried out economically.
Measuring principle
one. Measuring Principle of Magnetic Attraction and Thickness Gauge
The suction force between the magnet (probe) and the magnetic steel is proportional to the distance between the two, and this distance is the thickness of the cladding. Using this principle to make a thickness gauge, as long as the difference between the magnetic permeability of the coating and the base material is large enough, it can be measured. In view of the fact that most industrial products are stamped and formed by structural steel and hot-rolled cold-rolled steel plates, magnetic thickness gauges are the most widely used. The basic structure of the thickness gauge is composed of magnetic steel, relay spring, scale and self-stop mechanism. After the magnetic steel is attracted to the measured object, the measuring spring is gradually elongated thereafter, and the pulling force is gradually increased. When the pulling force is just greater than the suction force, the thickness of the coating can be obtained by recording the pulling force at the moment when the magnetic steel is detached. Newer products can automate this recording process. Different models have different ranges and applicable occasions.
