Type of paint used on spring surfaces
The oxidation treatment of the spring (also known as bluish, blackened, cooked black, etc.) is mainly used to prevent the corrosion of the spring, and also to make the spring appearance bright.Oxidation treatment methods include: alkaline oxidation, alkali free oxidation and electrolytic oxidation.
Spring oxidation treatment is often alkaline oxidation treatment, in the presence of oxidants (such as sodium nitrite) in caustic sodium solution.As the solution approaches the boiling point, the iron on the surface of the spring dissolves and forms sodium ferrite and sodium ferrite, which is then made of ferrous iron
Sodium sulfate interacts with sodium ferrite to form magnetic iron oxide (Pe3O4), or oxide film, with a thickness of about 0.5-1.5 microns.The color of the oxide film depends on the type of spring material and the surface state of the spring.Carbon steel springs are dark, while silicon-manganese steel springs are tan.
The oxide film is widely used as the surface protective layer of spring because of its beautiful color, large flexibility and lubricity, no hydrogen embrittlement, low price and high production efficiency.
Due to the lower corrosion resistance and wear resistance of the oxide film than other chemical films, in order to improve the corrosion resistance and lubrication performance of the oxide film, the phosphate can be added after oxidation treatment, or the oxidized spring can be re-soapy impregnation and oil coating treatment.