The corrosion of overlap wave spring can be divided into chemical corrosion and electrochemical corrosion according to the type of reaction. If the metal on the surface of the overlap wave spring simply reacts chemically with the surrounding medium, and the overlap wave spring causes corrosion, it is called chemical corrosion. For example, the spring is oxidized in a particularly dry atmosphere to form an oxide film, and the spring chemically changes with the liquid or impurities in the liquid in a non-electrolyte liquid, which belongs to chemical corrosion.
If the overlap wave spring is in contact with the electrolyte solution, the corrosion due to the action of the microbattery is called electrochemical corrosion. For example, the spring is in contact with acid or salt solutions. These solutions are electrolytes. Due to defects or impurities on the surface of the spring, electrodes with different potential differences are formed, so that the spring is continuously electrolytically corroded;
The chemical corrosion of the overlap wave spring is small and slow, while the electrochemical corrosion is the main and most common. But generally speaking, chemical corrosion and electrochemical corrosion exist at the same time.
Springs are often corroded by surrounding media during manufacturing, storage, and use. Since the overlap wave spring works by elastic force, the elastic force will change after the spring is corroded and loses its function. Therefore, preventing the corrosion of the overlap wave spring can ensure the stable operation of the spring and prolong its service life.
The anti-corrosion method of overlap wave spring generally adopts a protective layer. According to the nature of the protective layer, it can be divided into: metal protective layer, chemical protective layer, non-metallic protective layer, temporary protective layer, etc. The first three methods are introduced here.
One: The metal protective layer of the overlap wave spring:
Electroplating is an effective method to obtain a protective layer on the metal surface, and it is also the main method of spring anti-corrosion treatment. It is characterized by good adhesion of the coating, fine and tight crystallization, small porosity, uniform thickness, and good physical, chemical, and mechanical functions. Electroplating includes zinc plating, chrome plating, copper plating, tin plating, nickel plating, etc. The most common application is zinc plating.
Generally, after the galvanized layer is passivated, passivation can improve the protective performance of the coating and increase the appearance of the surface. Cadmium is relatively stable and has strong corrosion resistance for springs used in oceanic or high-temperature atmospheres, for springs in contact with seawater, and for hot water at 70°C. The cadmium coating is brighter and more beautiful than the zinc coating. The quality is softer, and the plasticity is better than that of the zinc coating. However, cadmium is scarce, expensive, and highly toxic, causing serious environmental pollution. Therefore, it is restricted in use. Therefore, most springs used only in the aviation, marine, and electronic industries use cadmium plating as a protective layer.
Two: The chemical protective layer of the overlap wave spring
The oxidation treatment of the spring is also called blackening. After the oxidation treatment, a protective magnetic iron oxide is produced on the surface of the spring with a thickness of about 0.62um. Due to the thin and porous film, the protection ability is poor. Therefore, oxidation treatment can only be used for anti-corrosion of springs that work in less corrosive media. Because the oxidation treatment cost is low, the process formula is simple, the production efficiency is high, and the characteristics of the spring are not affected, it is widely used in cold-formed small spring surface anticorrosion. In addition to oxidation treatment, there is also phosphating treatment. Phosphate films are relatively stable under atmospheric conditions. Its corrosion resistance is 2-10 times higher than that of oxidation treatment.
The methods of oxidation treatment include the salty oxidation method, the alkali-free oxidation method, and the electrolytic oxidation method. The most common is the alkaline oxidation method. The alkaline oxidation method involves heating the spring to around 140°C, immersing it in a sodium hydroxide solution containing an oxidant for a period of time, and then the oxidant and sodium hydroxide react with iron to produce sodium ferrite and sodium ferrite, which then react with each other to produce magnetic iron oxide.
Three: The non-metallic protective layer of the overlap wave spring
Painting is also one of the main methods of spring corrosion protection. It is mostly used in large and medium springs. Specifically, thermoformed and leaf springs.The paints used for springs mainly include: asphalt paint, phenolic paint, and epoxy paint. For some important springs, in order to improve the adhesion and corrosion resistance of the paint, the process of phosphating first and then painting is also adopted. The most commonly used painting methods are spray painting and dipping paint. With the development of process technology, in order to improve work efficiency, paint utilization rate, and paint quality, new technologies such as electrostatic spraying will be promoted.
So how to maintain the overlap wave spring in use?
The purpose of the maintenance work of the overlap wave spring machine is to ensure the normal operation of the spring machine, reduce the failure rate, and reduce the wear of the components, so as to achieve the purpose of prolonging the service life. Therefore, maintenance work is a very important part of the normal operation of the overlap wave spring machine.
- Routine maintenance. Routine maintenance centers around cleaning, tightening, adjusting, and lubricating. The daily maintenance of the overlap wave spring machine should be carried out before, during, and after the shift. This task is performed independently by the spring machine operator.
- Regular maintenance According to the maintenance requirements of various mechanical equipment, corresponding regular maintenance must be carried out after the specified working hours or specified mileage.
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