What is the anti-corrosion method of special screws?

Special screws are made of metal. There are four main methods to prevent metal corrosion, namely the nature of the material itself, the environment used, the interface between data and the environment, and the design of improved metal structures. If a complete corrosion-resistant alloy is used to manufacture a special screw, it is not realistic in economic concept unless there are special requirements, or completely isolate the environmental factors that cause corrosion on the surface of the special screw, which may not be feasible in practice or may be very difficult.

Improved metal structure design can improve the impact of special circumstances under certain conditions, but the design of most special screws cannot be completely modified, and its maintenance function is not eternal. Therefore, this method basically cannot solve this problem. As long as the interface is anticorrosive, that is, surface anticorrosive treatment, it is currently a widely used method.

Special screw surface anti-corrosion treatment refers to the use of various methods to apply a maintenance layer to the metal surface. Its function is to isolate the metal from the corrosive environment, thereby controlling the generation of the corrosion process, or reducing the contact between the corrosive medium and the metal surface, thereby avoiding or reducing corrosion.

The maintenance layer of special screws shall meet the following requirements:

1. Corrosion resistance, wear resistance and high hardness

2. The special screw structure is compact and complete, with small pores.

3. It is firmly separated from the base metal and has good adhesion.

4, uniform distribution, a certain thickness.

The maintenance layer of special screws is usually divided into metal coating and non-metal coating. Metal coating refers to a maintenance layer formed of a metal or alloy with strong corrosion resistance on a metal surface that is prone to corrosion. Such a coating is also referred to as a coating. There are many methods and types of production of metal coatings, the most common of which is electroplating, followed by molten metal dip coating (hot dip coating) and chemical surface treatment. Non-metallic coating refers to the maintenance layer formed on the surface of metal equipment or parts with organic polymer materials such as paint and inorganic materials such as ceramics. The maintenance layer can completely isolate the base metal from the environmental medium to avoid corrosion of the base metal due to contact corrosion in the medium of stainless steel standard parts.

The standard parts on the market mainly include carbon steel, stainless steel and copper. One is carbon steel. We distinguish alloy steel, high carbon steel, low carbon steel and medium carbon steel according to the carbon content in carbon steel.

Low carbon steel C%≤ 0.25% is commonly referred to as A3 steel in China. Mainly used for small special screws, grade 4 nuts, grade 4.8 bolts and other products without hardness requirements.

2. Carbon steel 0.25%

3. High carbon steel C%>0.45%. At present, the market is basically not used. Dongguan Screw Factory

4. Special screw alloy steel: Add alloying elements to ordinary carbon steel to increase some special properties of steel, such as 35, 40 chromium molybdenum, SCM435, 10b38. Aromatic screw mainly adopts SCM435 chromium molybdenum alloy steel, the main components are carbon, silicon, manganese, phosphorus, sulfur, chromium and molybdenum.