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Disc springs are often corroded by surrounding media during manufacturing, storage, and use. Since the disc spring works by elastic force, the elastic force of the disc spring will change and lose its function after being corroded. Therefore, preventing the disc spring from corrosion can ensure the stability of the disc spring and prolong its service life.
The method of placing the disc spring in a phosphate solution containing manganese, iron, and zinc to form a water-insoluble phosphate film on the metal surface is called phosphating.
Zinc phosphating and oiling are the standard anti-corrosion coating methods for disc springs in DIN 2093 and factory standards. During the phosphating process, the fine-crystalline phosphate precipitates on the base metal to form a protective film. If it is further combined with an oiled or waxed covering layer, the disc spring can obtain a more durable anti-corrosion effect. This kind of anti-corrosion method is usually used indoors or outdoors with rainproof measures.
The manganese phosphating coating has no anti-corrosion effect, but serves as a lubricating layer. A certain anti-corrosion effect can be obtained by oiling the manganese phosphated disc spring, which is only suitable for the transportation and storage of disc springs.
After oxidation treatment, protective magnetic iron oxide is formed on the surface of the disc spring. The oxide film is generally blue or black, and sometimes dark brown (the color depends on the surface state of the disc spring and the chemical composition of the disc spring material. Composition and oxidation treatment process). Although the oxide film can improve the corrosion resistance of the disc spring; but because the film is thin and has pores, its protection ability is poor, and it can only be used for disc springs that work in a less corrosive medium.
The oxidation treatment cost is low, the process formula is relatively simple, the production efficiency is high, and the oxide film has a certain degree of elasticity, which basically does not affect the characteristic curve of the disc spring. Therefore, oxidation treatment is widely used as anti-corrosion and decorative measures for forming spiral disc springs, disc spring washers and disc springs.
When the metal coating is separated from the solution, hydrogen will diffuse on the surface of the disc spring. This situation is more common when high-strength disc spring steel is used as a disc spring material. The disc spring after electroplating treatment must be treated in time to remove hydrogen. After electroplating, using a suitable heat treatment method (diffusion annealing) can reduce the tendency of hydrogen embrittlement, but it cannot completely eliminate it. Due to the influence of hydrogen embrittlement, electroplating should not be used as far as possible to apply anti-corrosion coating on the surface of the disc spring.
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