Steel structure bolts belong to the standard parts in hardware. You can see that most of the colors are black. Ordinary anchor screws are generally processed with ordinary carbon steel without quenching and tempering heat treatment. High-strength bolts are generally processed with high-quality carbon steel or alloy structural steel. They must undergo heat treatment process quenching and tempering heat treatment to improve comprehensive process performance. The solutions to the blackening of steel structure bolts mainly include the following aspects: 1. BRN solution In special-purpose mechanical equipment, special-purpose covalent bond modified engineering plastics are used to solve the problem. It has the advantages of good film bonding, unique surface color, good wear resistance, high surface density, controllable film thickness, no fading and no falling off, etc. 2. Organic chemical quenching and tempering heat treatment method Solve the steel structure bolts on special mechanical equipment, the film layer is firm, the combination is good; the color is unique; the wear resistance is good; the surface density is high. 3. Electrolytic salt water oxidation method The film layer is thick and black, and the film layer has poor sun resistance and is easy to burst automatically. 4. Organic chemical blackening method This method is divided into two types: acid-base blackening and alkaline blackening. Acid-alkaline blackening results in uniform film color, thin and firm, extremely plastic, and good bonding. However, the porous material of the film layer has poor wear resistance, and it needs to be solidified to improve wear resistance. The blackening time is relatively long with partial alkali, but the wear resistance of the black mucous membrane is very good, and it does not need to be coagulated to solve it.