Non destructive testing methods for coating thickness gauges
The non-destructive testing method and principle of coating thickness gauge: Coating thickness gauge is a highly comprehensive and promising discipline in practical measurement, which 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 industries such as chemical engineering, electronics, power, and metals, in order to achieve protection or decorative effects on various materials, methods such as spraying non-ferrous metal coatings and phosphating, anodizing, etc. are usually used. This has led to the emergence of concepts such as coatings, coatings, layers, or chemically generated films, which we refer to as "coatings".
The thickness measurement of the coating has become the most important process for users in the metal processing industry to conduct quality inspection 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 both domestically and internationally. The selection of non-destructive testing methods and instruments for coatings is becoming increasingly crucial with the gradual progress of material physical property research.
The non-destructive testing methods for coatings mainly include wedge cutting method, light cutting method, electrolysis method, thickness difference measurement method, weighing method, X-ray photoluminescence method, beta reflection method, capacitance method, magnetic measurement method, and eddy current measurement method. Most of these methods, except for the last five, require damage to the product or its surface, resulting in destructive testing. The measurement methods are cumbersome and slow, and are mostly suitable for sampling inspections.
X-ray and beta ray reflection methods can be used for non-contact non-destructive measurement, 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, which are generally used for measuring the thickness of each layer of metal coating.
The capacitance method is generally only used for testing the thickness of insulation coatings on very thin conductive materials.
Magnetic measurement method and eddy current measurement method, with the increasing progress of technology, especially in recent years with the introduction of microprocessor technology, thickness gauges have taken a big step towards miniaturization, intelligence, multifunctionality, high precision, and practicality. The resolution of the measurement has reached 0.1 μ m, and the accuracy can reach 1%. It also has the characteristics of wide applicability, wide range, easy operation, and low cost. It is the most widely used instrument in industry and scientific research.
The use of non-destructive testing methods to measure thickness does not damage the coating or substrate, and the testing speed is fast, thus enabling a large amount of testing work to be carried out economically. The following introduces several conventional thickness measurement methods.
