Surface treatment of screws
Screw fasteners in order to meet the needs of the product, will generally use the surface treatment process to meet the requirements of customers, some are the change of the surface treatment of hardware screws, some are the change of the performance of screws, so what material is suitable for what surface treatment, what kind of surface treatment can achieve anti-rust performance? General screw to a simple introduction to the common screw fastener surface treatment process includes what and their respective characteristics.
1. Environmental nickel. Generally refers to the nickel or zinc nickel alloy after the product does not contain limited harmful substances, to do environmental protection nickel (in line with ROHS standards) is very simple, after plating can not be passivated with hexavalent chromium (of course, ROHS inside the other five can not have), need to solve the problem of anti-discoloration. Different from antirust nickel, antirust nickel is mainly characterized by antirust, antirust nickel surface treatment with a layer of antirust oil, there is a certain antirust effect, generally can pass the salt spray test for 48 hours, and environmental protection nickel is not over the salt spray test, because it has no antirust effect. Generally suitable for environmental protection nickel and rust-proof nickel surface treatment materials are carbon steel, copper.
2. Environmental black zinc, can pass the salt spray test for 48 hours, applicable materials are: copper, iron, stainless steel, it is worth noting that: general stainless steel screw surface plating environmental protection black zinc occasionally peeling phenomenon, but a large number of stainless steel screw products electroplating environmental protection black zinc can avoid this kind of situation.
3. The use of chemical or electrochemical method, a layer of coloured film on metal surface or interfere with the film, the film is very thin, sometimes interfere with the film itself has almost no color, and when the surface of the metal and membrane occurs when light reflex, light waves in the offset each other, forming a variety of different color, when the thickness of the film gradually diminishing, tonal change, generally from yellow, red, blue or green, until the show The color of the film itself. If the thickness of the film is not uniform, it will produce a rainbow color or Mosaic. Color zinc plating on the surface of screw fasteners can pass 4. Salt spray test for 96 hours, suitable for carbon steel.
4. Dachro, Dachro surface treatment can be plated in three colors: black, silver gray, silver white. The biggest feature of Dachro surface treatment is its good rust resistance. Dacro screw can pass 500 hours salt spray test without red rust, 72 hours without white rust, but suitable for dacro surface treatment materials are carbon steel, stainless steel.
5. Tin plating, high temperature tin (260 plating 2 minutes, high temperature welding) if the customer does not have clear requirements, it will generally do ordinary tin surface treatment. Suitable for tin plating material is: iron.