The seven anti-corrosion treatment methods of fasteners are briefly described
For the use of fasteners, anti-corrosion treatment is an important link, according to different corrosion conditions can take different treatment methods.
Since blackening has little protection against rust, it will rust quickly without oil. Blackened square post formwork torque-preload consistency is also poor. If you need to improve, you can apply grease on the inner thread during assembly before screwing.
2 zinc infiltration
Zincizing is zinc powder solid metallurgical thermal diffusion coating. Its uniformity is good, thread, blind hole can obtain uniform layer, the processing process is pollution-free, environmental protection.
3 electric galvanizing
Hydrogen embrittleness is easy to occur in the process of electric galvanizing, and the consistency is poor. A square column template with a height of 500 is selected for docking and assembly, and attention should be paid to the anastomosis of the card slot interface during docking and assembly. Take an auxiliary support, open it, stick it on the wooden square where the two square column templates are joined according to the marked position, tighten it on the other side of the same height to make a position mark 150mm above the ground. A square column template with a height of 1000mm was spliced with a square column template with a height of 500mm, and then the auxiliary support was used to clamp it in the marked position. Then clamp it with an auxiliary bracket. First, a single piece of elbow clamp is horizontally placed on the auxiliary support. Place the elbow upward, pass the tail end of the second clamp through the bending space of the clamp head end, and then place it horizontally on the auxiliary support. , and unstable, generally not used for the connection of important parts. In order to improve the torque-preload consistency, the method of coating lubricating substance after plating can also be used to improve and increase the torque.
4 Cadmium plating
The corrosion resistance of cadmium coating is very good, especially in the Marine atmosphere environment, corrosion resistance is better than other surface treatment. In the process of processing cadmium plating, the waste liquid treatment cost is large and the cost is high. Its price is about 15~20 times that of galvanizing. Therefore, it is not used in the general industry. It is suitable for fasteners for oil drilling platforms and HNA aircraft.
5 chromium plating
Chromium coating in the atmosphere is very stable, not easy to discolor and tarnish, high hardness and wear resistance. Chrome plating on fasteners is generally used for decorative purposes.
Two kinds of fastener phosphating are commonly used: zinc phosphating and manganese phosphating. The lubrication performance of zinc phosphating is better than that of manganese phosphating, and the corrosion resistance and wear resistance of manganese phosphating are better. Many industrial fasteners are coated with phosphating oil. Because its torque – preload consistency is very good, assembly can ensure to meet the expected fastening requirements of the design, so it is used in the industry more, especially for the connection of some important parts.
7 silver plating, nickel plating
Silver coating can not only prevent corrosion, but also be used as solid lubricant for fasteners. For cost reasons, nuts are silver plated, bolts are not, and sometimes small bolts are silver plated. Nickel plating of fasteners is mainly used in places where corrosion protection and good electrical conductivity are required.