Briefly describe the anti-corrosion method of screws

Stainless steel screws are made of metal, and there are four main ways to prevent metal corrosion, namely the nature of the material, the environment used, the interface between the data and the environment, and the design of the improved metal structure. If a complete corrosion-resistant alloy is used to manufacture stainless steel screws Unless there are special requirements, it is unrealistic in terms of economy, or the complete separation of the appearance of the screw from the corrosive environmental elements is not practical in practice and may be very difficult. Improving the design of the metal structure can improve the impact of special circumstances under certain conditions, but most stainless steel screw designs cannot be fully revised, and their maintenance is not permanent, so this method cannot basically deal with the problem, as long as it is on the interface. Anti-corrosion, that is, external anti-corrosion treatment is currently the most widely used method.

The anti-corrosion treatment of the screw surface refers to the use of various methods to apply a maintenance layer on the metal surface. Its role is to isolate the metal from the corrosive environment to suppress the corrosion process, or reduce the contact between the corrosive medium and the metal surface, and avoid Or the purpose of reducing corrosion.

The maintenance layer should be able to meet the following requirements:

1. Corrosion resistance, wear resistance, high hardness,

2. The structure is tight, intact and has small pores.

3. Separate from the base metal, strong and good adhesion.

4. Spread evenly and have a certain thickness.

The maintenance layer is usually divided into two types: metallic coating and non-metallic coating. Metal coating refers to using a metal or alloy with strong corrosion resistance to form a maintenance layer on the surface of easily corroded metal. This coating is also called plating. There are quite a few ways and varieties of metal plating, the most common of which is electroplating, followed by molten metal dip plating (hot dip plating) and chemical surface treatment. Non-metallic coating refers to the use of organic polymer materials such as paint and inorganic materials such as ceramics to form a maintenance layer on the surface of metal equipment or parts. This maintenance layer can completely isolate the base metal from the environmental medium to avoid contact corrosion of the base metal due to contact Corrosion occurs in the medium of stainless steel standard parts.