Non-destructive testing methods and principles for measuring coating thickness
Non-destructive testing methods and principles of coating thickness gauge: In actual measurement, coating thickness gauge is a promising subject that is highly comprehensive in theory and attaches great importance to practical aspects. It involves many aspects such as the physical properties of materials, product design, manufacturing processes, fracture mechanics, and finite element calculations.
In the chemical, electronic, electric power, metal and other industries, in order to protect or decorate various materials, spraying non-ferrous metal covering, phosphating, anodizing and other methods are usually used. In this way, coatings, plating, plating, etc. Concepts such as layers, laminates or chemically formed films are called "coverings".
The thickness measurement of the coating has become the most important process necessary for the metal processing industry and users to inspect the quality of finished products. It is a necessary means for products to meet standards. At present, the thickness of coatings has been generally measured according to unified international standards at home and abroad. The choice of non-destructive testing methods and instruments for coatings has become more important with the gradual progress in research on the physical properties of materials.
Relevant non-destructive testing methods for coatings mainly include: wedge cutting method, light interception method, electrolysis method, thickness difference measurement method, weighing method, X-ray fluorescence method, β-ray reflection method, capacitance method, magnetic measurement method and eddy current measurement Law etc. Most of these methods, except for the last five, will damage the product or the surface of the product. They are destructive testing. The measurement methods are cumbersome and slow, and they are mostly suitable for sampling inspection.
X-ray and β-ray reflection methods can perform non-contact and non-destructive measurements, but the devices are complex and expensive and the measurement range is small. Because there is a radioactive source, users must comply with radiation protection regulations. It is generally used to measure the thickness of each layer of metal coating.
The capacitance method is generally only used to test the insulation coating thickness of very thin conductors.
Magnetic measurement method and eddy current measurement method, with the increasing advancement of technology, especially after the introduction of microprocessor technology in recent years, thickness gauges have taken a big step towards miniaturization, intelligence, multi-function, high precision and practicality. The measurement resolution has reached 0.1μm, and the accuracy can reach 1%. It also has the characteristics of wide application range, wide measuring range, easy operation and low price. It is the most widely used instrument in industry and scientific research.
The thickness measurement using non-destructive testing method neither destroys the coating nor the base material, and the detection speed is fast, so a large amount of detection work can be carried out economically. Several conventional thickness measurement methods are introduced below.
