What are the galvanizing methods for common safety bolts and safety nuts?
1. Hot-dip galvanizing
Hot-dip galvanizing is also commonly referred to as hot-dip galvanizing. Hot-dip galvanizing is a process and method in which pre-treated steel parts are put into a molten zinc solution to form a zinc and (or) zinc-iron alloy coating on the surface to obtain a metal coating. Hot-dip galvanizing has a wide range of applications, such as hot-dip galvanized highway traffic barriers (highway corrugated beam steel guardrail fastener connection pair), hot-dip galvanized fasteners and other fasteners widely used in pipelines and power transmission Fasteners etc. The service life of hot-dip galvanizing is not only related to the process itself, but also directly related to the adhesion of the galvanized layer.
The hot-dip galvanized layer has good coverage and protection ability, and its ability to resist atmospheric corrosion is better than that of electro-galvanized.
2. Powder sherardizing
Powder galvanizing is a surface treatment process that uses zinc dipping agent as the source of zinc, and generates zinc by heating, and interdiffusion of iron atoms to form a zinc-impregnated layer (zinc-iron alloy layer) on the surface of steel. The main component of powder sherardizing is pure zinc powder, which is added with appropriate amount of filler materials such as alumina, fireclay and ammonium chloride.
The most prominent feature of powder galvanizing is not an external coating, but the base metal and the galvanizing layer form an organic whole, so the combination is very strong. The hardness and corrosion resistance of the powder galvanized layer are much better than that of the electro-galvanized layer.
The powder zinc-seeding process is to bury the surface-treated workpiece in a sealed container filled with powder zinc-seeding agent, heat it to below the melting point of zinc, keep it warm for a certain period of time, and then cool it to room temperature with the furnace.
The most prominent feature of powder sherardizing is that the sherardizing layer is uniform, without ammonia embrittlement, and almost without deformation. It is especially suitable for surface anti-corrosion treatment of nuts, bolts and other fasteners, hardware products, workpieces with complex shapes and powder metallurgy products.
3. Mechanical sherardizing
Mechanical galvanizing is the use of impact media (such as glass balls) to impact and collide with the surface of steel parts in the presence of galvanizing powder, dispersant, accelerator, liquid medium (usually water), etc. The surface treatment process that forms the galvanized layer.
The mechanical galvanizing layer is a kind of anti-corrosion layer formed by a completely different process from electro-galvanizing and hot-dip galvanizing.
Process features: production operation at room temperature, through the rotation of the plating cylinder loaded with parts, the impact medium in the cylinder will collide with the parts to generate mechanical impact force with the rotation of the cylinder, and the plating powder will collide and deposit on the surface of the workpiece, thus forming A coating having the basic physical characteristics of metallic zinc.
Process characteristics: The galvanizing process of the mechanical galvanizing process does not cause hydrogen embrittlement hazards to high-strength steel.
Process defects: there is unevenness in the thickness of the zinc layer; the zinc layer is not as smooth and bright as the electroplating layer.
Electrogalvanizing is a very common surface treatment method and process technology in the manufacture of fastener products.
The electro-galvanized layer is a typical anodic coating, which is mainly used to improve the anti-corrosion performance of the substrate. Due to its thin coating thickness, it is mainly used for surface anti-corrosion protection under general environmental conditions.
After chromate passivation treatment, its anti-corrosion performance is greatly improved. The excellent electro-galvanized layer can be used for neutral outdoor protection, but its anti-corrosion performance is relatively poor in harsh industrial atmospheres and coastal climates.
Electrogalvanized surface treatment method and process technology, low cost, stable and reliable process, easy to use. However, hydrogen embrittlement is very easy to occur, so hydrogen treatment should be carried out in time after electro-galvanizing. In addition, the acid and alkali resistance is poor, the anticorrosion time is short, and the environmental protection of the process is low.