Method of galvanizing fasteners

1. Hot dip galvanizing

Hot-dip galvanizing is also commonly known as hot-dip galvanizing

Hot dip galvanizing is the process and method of entering the pre-treated steel parts into the molten zinc liquid, forming zinc and (or) zinc-iron alloy coating on its surface, so as to obtain a metal covering layer.

The application of hot dip galvanizing is extremely wide, such as hot dip galvanizing highway traffic barrier (fastener connection of highway corrugated beam steel guardrail), hot dip galvanizing fasteners and other fasteners widely used in pipelines and power transmission.

In addition to the process itself, the service life of hot dip galvanizing is directly related to the amount of adhesion of the galvanizing layer.

Hot-dip galvanizing layer has good covering and protection ability, and the ability to resist atmospheric corrosion is better than that of electric galvanizing.

2. Powder zincizing

Powder zincizing is a surface treatment process in which zinc impregnating layer (zinc-iron alloy layer) is obtained by heating zinc from zinc impregnating agent as zinc source.

The main component of powder zincizing is pure zinc powder, in which an appropriate amount of filling materials such as alumina, refractory clay and ammonium chloride are added.

The most prominent feature of powder zincizing is not an external coating, but the matrix metal and the infiltration layer constitute an organic whole, so the combination is very firm. The hardness and corrosion resistance of powder zincizing layer are much better than that of electrogalvanizing layer.

Powder zincizing process is to bury the surface treated workpiece in a sealed container containing powder zincizing agent, heat it to the melting point of zinc, hold it for a certain time, and then cool it to room temperature with the furnace.

The most prominent feature of powder zincizing is that the infiltration layer is uniform, there is no ammonia embrittlement, and there is almost no deformation. Especially suitable for nuts, bolts and other fasteners and hardware products, complex shape of the workpiece and powder metallurgy products surface anti-corrosion treatment process.

3. Mechanical galvanizing

Mechanical galvanizing is in the presence of zinc powder and dispersant, accelerator, liquid medium (usually water) and other substances under the conditions, the use of impact media (such as glass balls), impact impact on the surface of steel, and the formation of galvanized layer on the surface of the workpiece surface treatment process.

Mechanical galvanizing layer is a kind of anticorrosive coating formed by a completely different process from electric galvanizing and hot dip galvanizing.

Process characteristics: Production operation under room temperature conditions, through the rotation of the plating cylinder of the loaded parts, the impact medium in the cylinder with the rotation of the drum, and the parts collide with each other to produce mechanical impact, and the zinc powder is deposited on the surface of the parts, thus forming a coating with the basic physical characteristics of metal zinc.

Process characteristics: The galvanizing process of mechanical galvanizing process does not cause hydrogen embrittlement harm to high-strength steel.

Process defects: uneven thickness of zinc layer; Zinc layer is not as smooth and bright as electroplating layer.

4. Electric galvanizing

Electrogalvanizing is the most common surface treatment method and process technology in the manufacture of fastener products.

Electrogalvanizing layer is a typical anodic coating, which is mainly used to improve the corrosion resistance of the substrate. Because of its thin coating thickness, it is mainly used for surface anti-corrosion protection under general environmental conditions.

After chromate passivation treatment, its corrosion resistance is greatly improved, and the excellent galvanizing layer can be used for neutral outdoor protection, but the corrosion resistance is poor in the harsh industrial atmosphere and coastal climate.

Electrogalvanizing surface treatment method and process technology, low cost, stable and reliable process, easy to use. However, it is very easy to produce hydrogen embrittlement, so it should be dehydrogenated in time after electrogalvanizing. In addition, the acid and alkaline resistance is poor, the corrosion time is short, and the environmental protection of the process is low.