One, cadmium plating
Cadmium coating has very better corrosion resistance, so some Socket head screws manufacturers will use cadmium plating to enhance the rust resistance of bolts, but because the waste liquid generated during cadmium electroplating will be more expensive when processed. It is more expensive, so it is more suitable for surface treatment of Socket head screws used in airplanes and oil drilling platforms.
Second, sherardizing
Sherardizing is a commonly used fastener surface anti-rust treatment process, which belongs to the zinc powder solid metallurgical thermal diffusion coating. Because of its good uniformity, it can be spread evenly in the threads and blind holes, and it will not pollute the environment during processing.
Three, electro-galvanized
Electro-galvanizing is also a common anti-rust treatment method for the surface of Socket head screws, but because hydrogen embrittlement is more likely to occur during the galvanizing process, in order to maintain the consistency of the bolt pre-tightening force, you can apply lubrication after galvanizing Substance to enhance the torque of the bolt.
Four, chrome plating
The stability of the chrome coating is very good, and after chrome plating, the surface of Socket head screws will still maintain luster, and will increase the wear resistance of the bolts, so many decorative Socket head screws will use this type for rust prevention. method.
