Methods of anti-corrosion of screws

There are four main methods for metal corrosion prevention, namely, control the material itself, the use environment, the interface between the material and the environment, and the design of improving the metal structure. If a completely corrosion-resistant alloy is used to manufacture screws, unless there is special need, it will be economical. The point of view is impractical, or to completely isolate the surface of the screw from environmental factors that will cause corrosion, it may not be feasible in practice, and it may be very difficult. Improved metal structure design can improve the impact of special circumstances under certain circumstances, but the design of most screws cannot be fully modified, and its protective effect is not permanent. Therefore, this method cannot fundamentally solve the problem, only the anti-corrosion on the interface , That is, surface anti-corrosion treatment is currently the most widely used method.

Surface anti-corrosion treatment refers to the use of various methods to apply a protective layer on the metal surface. Its function is to isolate the metal from the corrosive environment to inhibit the corrosion process or reduce the contact between the corrosive medium and the metal surface. To achieve the purpose of preventing or reducing corrosion. The protective layer should meet the following requirements:

1. Corrosion resistance, wear resistance, high hardness

2. Tight structure, complete, small pores (Guide: Tips on stainless steel fasteners)

3. It is firmly bonded to the base metal and has good adhesion

4. Evenly distributed and a certain thickness. The protective layer is usually divided into two types: metal coating and non-metal coating. Metal coating refers to the use of a metal or alloy with strong corrosion resistance to form a protective layer on the surface of the easily corroded metal. This kind of coating is also called plating. There are many methods and types of metal coatings, the most common of which is electroplating, followed by molten metal immersion 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 protective layer on the surface of metal equipment or parts. The protective layer can completely isolate the base metal from the environmental medium and prevent the base metal from being corroded by contact. Medium and cause corrosion.

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