Surface treatment and coating detection of fasteners based on
Surface treatment technology refers to the process of artificially forming a surface layer with different mechanical, physical and chemical properties from the substrate on the surface of the substrate material. The purpose of surface treatment is to meet the corrosion resistance, wear resistance, decoration or other special functional requirements of the product.
Main considerations when selecting fastener surface treatment technology:
1) The surface treated coating must be firmly attached and cannot fall off during installation and disassembly. For threaded fasteners, the coating should be thin enough to make the plated threads still screw together.
2) Generally, the temperature limit of coating is lower than that of fastener material, so it is also necessary to consider the working temperature requirements of fasteners.
3) For surface treatment, besides paying attention to aesthetics and corrosion prevention, the factors of fasteners, that is, the consistency of installation torque and preload, should also be considered.
The most common testing items of coating are coating thickness and salt spray test. Coating thickness can be detected by metallographic method, X-ray fluorescence method, stripping method, magnetic method and so on, depending on the type and shape of the test piece. Salt spray test is divided into neutral salt spray test, acetic acid salt spray test, copper accelerated acetate test and so on, which are suitable for different coatings.