Most springs are used in different types of corrosive environments. Due to the action of chemical corrosion and electrochemical corrosion, the surface of the spring will be corroded to varying degrees, which will cause the spring to be damaged prematurely, so anti-corrosion treatment must be carried out. The anti-corrosion treatment of the spring is to cover the surface of the spring with anti-corrosion materials to form a protective layer, and the protective layer separates the spring from the corrosive medium to achieve the purpose of anti-corrosion.
There are three commonly used methods of spring anti-corrosion: electroplating, oxidation, and painting. Electroplating 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 and nickel plating, etc. The most common application is zinc plating.
The surface of spring galvanized is generally white or colored. Zinc hardly changes in dry air. In humid air or water containing carbon dioxide, a white zinc oxide film will be produced, and this film can play a role in corrosion inhibition. The zinc coating is suitable for use in various atmospheric conditions, but the corrosion resistance of zinc is poor in aqueous solutions containing acids, alkalis, and salts and in pure marine atmospheric conditions.
Galvanized is characterized by low cost, simple process and good effect, so it is widely used in the anti-corrosion of small and medium-sized springs in the atmosphere. After the spring is galvanized, it should be passivated and dehydrogenated to improve the anti-corrosion ability of the spring and avoid hydrogen embrittlement. Especially small springs are more prone to hydrogen embrittlement, so special attention must be paid to pickling and electroplating. Oxidation treatment The oxidation treatment of the spring is also called bluing or blackening. After the oxidation treatment, a protective magnetic iron oxide is produced on the surface of the spring, with a thickness of about 0.6~2um. 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, so 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. Painting Painting is also one of the main methods of spring corrosion protection. Mostly used in large and medium springs. Especially thermoformed springs 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 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.