Galvanizing refers to a surface treatment technology that coats the surface of metal, alloy or other materials with a layer of zinc for aesthetics and rust prevention. The main method used is hot-dip galvanizing, which also includes cold-dip galvanizing and mechanical galvanizing. The types of galvanized products can be divided into galvanized sheet coils and galvanized structural parts. The main terminal flows include infrastructure, real estate, automobiles and other fields.
Zinc is easily soluble in acid and also soluble in alkali. Zinc changes little in dry air. In humid air, a dense basic zinc carbonate film will form on the zinc surface. In atmospheres containing sulfur dioxide, HS and marine atmospheres, zinc has poor corrosion resistance. Especially in atmospheres with high temperature, high humidity and organic acids, the zinc coating is easily corroded.
The standard electrode potential of zinc is -0.76V. For steel substrates, zinc coating is an anodic coating. It is mainly used to prevent corrosion of steel. Its protective performance is closely related to the thickness of the coating. After the zinc coating is passivated, dyed or coated with gloss protectant, its protective and decorative properties can be significantly improved.
Process method
Hot-dip galvanizing: also called hot-dip galvanizing and hot-dip galvanizing: it is an effective method of metal anti-corrosion and is mainly used for metal structural facilities in various industries. It is to immerse the rust-removed steel parts into molten zinc liquid at about 500°C, so that the zinc layer is attached to the surface of the steel components, thereby achieving the purpose of anti-corrosion.
Cold galvanizing: It is electro-galvanizing. The amount of zinc is small, only 10-50g/m2. It is a process that uses electrolysis to attach a metal film to the surface of metal or other material parts to form a uniform, dense and good bonding force. The metal layer process can prevent corrosion, improve wear resistance, conductivity, reflectivity and enhance aesthetics.
Mechanical galvanizing is in a rotating drum filled with plated parts, glass balls, zinc powder, water and accelerator. The glass balls as the impact medium rotate with the drum, friction and hammering with the surface of the plated parts to generate mechanical physical energy. , under the action of chemical accelerators, the plated zinc powder is "cold welded" to the surface of the plated parts to form a smooth, uniform and delicate coating with a certain thickness.
The difference between hot dip galvanizing and cold galvanizing:
1. The anti-corrosion properties are different. Hot-dip galvanizing is dozens of times better than cold-dip galvanizing.
2. The working methods are different: hot-dip galvanizing is zinc plated in molten zinc liquid at 450-480 degrees, while cold plating is zinc plated by electroplating or other methods at room temperature.
3. The thickness of the galvanized layer is different. The thickness of hot-dip galvanizing is much larger than that of cold-dip galvanizing.
4. The surface smoothness is different. The surface of cold galvanizing is smoother and more beautiful than hot dip galvanizing.
5. The prices are different. The price of hot-dip galvanizing is higher than that of cold-dip galvanizing.
6. Cold galvanizing can only be plated on one side, while hot dip galvanizing must be fully plated.
7. The adhesion is different. The adhesion of cold galvanizing is not as good as that of hot dip galvanizing.
8. The charging standards are different. Hot-dip galvanizing is charged according to the thickness of the material, while cold plating is mostly charged according to square meters. The main application areas of the hot-dip galvanizing process are: industry, construction, electric power facilities, chemical facilities, machinery manufacturing, petroleum, municipal facilities, agricultural facilities, communication facilities, fire protection facilities, railways, highway transportation facilities and other fields.
