Factors affecting layer coating thickness gauges and their principles
Non-destructive testing technology is a promising discipline that is theoretically comprehensive and attaches great importance to the practical aspects. It involves the physical properties of materials, product design, manufacturing process, fracture mechanics and finite element calculation and many other aspects.
In the chemical, electronics, electric power, metal and other industries, in order to achieve the protection of various types of materials or decorative effect, usually using spraying, non-ferrous metal covering and phosphating, anodic oxidation treatment, etc., so that the emergence of the concept of coatings, plating, dressing, paste layer or chemically generated film, which we call "cladding".
The thickness measurement of the cladding has become a zui important process for metal processing industry users to carry out quality inspection of finished products. Is a product to meet the standards of the necessary means. At present, domestic and foreign has been generally in accordance with the unified international standards to determine the thickness of the coating layer, cladding nondestructive testing methods and instrumentation selection with the gradual progress in the study of the physical properties of the material and the more critical.
About the cladding nondestructive testing methods, there are: wedge cut method, light cut-off method, electrolysis method, thickness difference measurement method, weighing method, X-ray Perspex method, β-ray reflection method, capacitance method, magnetic measurement method and eddy current measurement method and so on. Most of these methods, except for the latter five, have to damage the product or the product surface, is a loss-making test, measurement means cumbersome, slow, and more applicable to sampling inspection.
X-ray and β-ray reflection method can be non-contact non-destructive measurement, but the device is complex and expensive, the measurement range is small. Because of the radioactive source, so the user must comply with the specifications of radiation protection, generally used in various layers of metal plating thickness measurement.
Capacitance method is generally used only in very thin conductive body insulation cladding thickness test on the application.
Magnetic measurement method and eddy current measurement method. With the increasing progress of technology, especially in recent years after the introduction of microprocessor technology, thickness gauge to miniature, intelligent, multi-functional, high-precision, practical aspects of a big step forward. Measurement resolution has reached 0.1μm, accuracy can reach 1%. And has a wide range of applications, wide range, easy to operate, inexpensive and so on. It is a widely used instrument in industry and scientific research.
The use of non-destructive testing methods to measure the thickness of both non-destructive cladding does not destroy the substrate, fast detection speed, so a large number of tests can be carried out economically. The following are introduced several conventional thickness measurement methods.
