Principles of Conventional Coating Thickness Gauges
The covering layer formed for surface protection and decoration of materials, such as coatings, plating layers, coatings, stickers, chemically generated films, etc., is called coating in relevant national and international standards.
Coating thickness measurement has become an important part of the processing industry and surface engineering quality inspection, and is a necessary means for products to achieve excellent quality standards. In order to internationalize our products, there are clear requirements for the thickness of the coating in China's exported goods and foreign-related projects.
The main methods for measuring coating thickness include wedge cutting method, light cutting method, electrolysis method, thickness difference measurement method, weighing method, X-ray fluorescence method, beta ray backscatter method, capacitance method, magnetic measurement method, and eddy current measurement method. The first five of these methods are destructive detection, which has cumbersome measurement methods and slow speed, and is mostly suitable for sampling inspection of the principle of conventional coating thickness gauges.
The X-ray and beta ray methods are non-contact non-destructive measurements, but the equipment is 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 beta ray method is suitable for measuring coatings and substrates with atomic numbers greater than 3. The capacitance method is only used for measuring the thickness of insulation coatings on thin conductors.
With the continuous advancement of technology, especially the introduction of microcomputer technology in recent years, thickness gauges using magnetic and eddy current methods have made further progress towards miniaturization, intelligence, multifunctionality, high precision, and practicality. The resolution of the measurement has reached 0.1 microns, and the accuracy can reach 1%, which has been greatly improved. It has a wide range of applications, a wide measuring range, easy operation, and low cost, making it a widely used thickness measuring instrument in industry and scientific research.
The use of non-destructive methods does not damage the coating or substrate, and has a fast detection speed, which can economically carry out a large amount of testing work.
