1. Oxidation
Since blackening has almost no anti-rust ability, it will rust very quickly without oil. Blackened square column formwork torque-preload consistency is also poor. If you need to improve, you can apply grease on the inner thread during assembly and then screw it together.
2. Zinc
Sherardizing is a solid metallurgical thermal diffusion coating of zinc powder. The uniformity is good, the uniform layer can be obtained in the thread and the blind hole, and the processing process is pollution-free and environmentally friendly.
3. Electro galvanized
The electro-galvanizing process is prone to hydrogen embrittlement, and the consistency is poor. Take a square column template with a height of 500 and assemble it. Pay attention to the fit of the card slot interface during butt assembly. Take an auxiliary bracket, open the auxiliary bracket, clamp the auxiliary bracket on the wooden square where the two square column templates are spliced according to the marked position, and tighten it on the other side of the same height to make a position mark 150mm above the ground. Take a square column template with a height of 1000mm and splicing it with a square column template with a height of 500mm, and then use the auxiliary bracket to clamp it at the marked position. Then clamp it with the auxiliary bracket. First place a single-piece elbow clamp piece horizontally on the auxiliary bracket. Place the elbow upwards, pass the end of the second piece of clamp through the bending space at the head end of the piece of clamp, 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 substances after plating can also be used to improve and increase the torque.
4. Electroplating of cadmium
The corrosion resistance of cadmium coating is very good, especially in the marine atmosphere, the corrosion resistance is better than other surface treatments. The waste liquid treatment cost in the process of electroplating cadmium is high and the cost is high, and its price is about 15~20 times that of electroplating. Therefore, it is not used in general industries, but it is suitable for Screws and Bolts for oil drilling platforms and HNA aircraft.
5. Electroplating chrome
Chrome plating is very stable in the atmosphere, not easy to change color and tarnish, and has high hardness and good wear resistance. Chrome plating on Screws and Bolts is generally used for decorative purposes.
6. Phosphating
There are two commonly used phosphating in Screws and Bolts: zinc phosphating and manganese phosphating. Zinc-based phosphating has better lubricating properties than manganese-based phosphating, and manganese-based phosphating has better corrosion resistance and wear resistance. Many industrial Screws and Bolts are treated with phosphating oil. Because its torque-preload consistency is very good, and it can ensure the tightening requirements expected by the design during assembly, it is widely used in the industry, especially the connection of some important parts.
7, silver-plated, nickel-plated
Silver plating can both prevent corrosion and act as a solid lubricant for fasteners. For cost reasons, the nuts are silver-plated, the bolts are not, and sometimes small bolts are also silver-plated. Fasteners are nickel-plated, mainly used in places where both anti-corrosion and good electrical conductivity are required. Such as vehicle battery lead-out terminals, etc.
