The principle of conventional coating thickness gauge
The covering layer formed to protect and decorate the surface of the material, such as coating, plating, coating, lamination, 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 the processing industry and surface engineering, and is an essential means for products to meet excellent quality standards. In order to internationalize products, my country's export commodities and foreign-related projects have clear requirements for the thickness of the coating.
The main methods for measuring coating thickness include: wedge cutting method, light interception 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. The first five of these methods are destructive testing. The measurement methods are cumbersome and slow, and they are mostly suitable for sampling inspection.
X-ray and β-ray methods are non-contact and non-destructive measurements, but the devices are complex and expensive, and the measurement range is small. Due to the presence of radioactive sources, users must comply with radiation protection regulations. The X-ray method can measure extremely thin coatings, double coatings, and alloy coatings. The β-ray method is suitable for measurement of coatings and coatings with substrate atomic numbers greater than 3. The capacitance method is only used when measuring the thickness of insulating coatings on thin conductors.
With the increasing advancement of technology, especially after the introduction of microcomputer technology in recent years, thickness gauges using magnetic methods and eddy current methods have taken a step closer to becoming miniaturized, intelligent, multi-functional, high-precision and practical. The measurement resolution has reached 0.1 micron, and the accuracy can reach 1%, which has been greatly improved. It has wide application range, wide measuring range, easy operation and low price. It is the most widely used thickness measuring instrument in industry and scientific research.
The non-destructive method neither destroys the coating nor the substrate, and the detection speed is fast, allowing a large number of inspections to be carried out economically.
