What is galvanizing?
Galvanizing is a surface treatment technique that applies a layer of zinc to the surface of a metal, alloy or other material for aesthetic and rust prevention purposes. The main method used is hot-dip galvanizing, which also includes cold-dip galvanizing and mechanical galvanizing.
Galvanized products can be divided into galvanized sheet and coil and galvanized structural parts. The main end-use streams include infrastructure, real estate, and automotive.
Zinc is readily soluble in acids and also in bases. Zinc hardly changes in dry air. In humid air, a dense film of alkaline zinc carbonate is formed on the zinc surface. In atmospheres containing sulfur dioxide, HS and marine atmospheres, zinc is less resistant to corrosion, especially in high temperature highly humid atmospheres containing organic acids, where zinc plating is extremely susceptible to corrosion.
The standard electrode potential of zinc is -0.76V. For steel substrates, zinc plating is an anodic layer, which is mainly used to prevent corrosion of steel, and its protective performance is highly dependent on the thickness of the plating. The protective and decorative properties of zinc plating can be significantly improved by passivation, dyeing or coating with light protector.
Process Method
Hot-dip galvanizing: also called hot-dip galvanizing and hot-dip galvanizing: is an effective way of metal corrosion protection, mainly used on metal structural facilities in various industries. It is the process of immersing the descaled steel parts into the melted zinc solution at about 500°C, so that a zinc layer is attached to the surface of the steel parts, thus serving the purpose of corrosion protection.
Cold galvanizing: This is the process of electroplating zinc with a small amount of zinc, only 10-50g/m2. It is the process of using electrolysis to attach a metal film to the surface of metal or other materials to form a uniform, dense, and well-bonded metal layer that prevents corrosion, improves wear resistance, electrical conductivity, reflectivity, and enhances aesthetics.
Mechanical Galvanizing
In a rotating barrel containing plated parts, glass balls, zinc powder, water and accelerator, the glass balls, as the impact medium, rotate with the barrel and generate mechanical physical energy by friction and hammering with the surface of the plated parts, and with the action of the chemical accelerator, the zinc powder is “cold-welded” to the surface of the plated parts, forming a smooth, uniform and detailed layer of a certain thickness. thickness.
The difference between hot and cold galvanizing.
1. Corrosion resistance is different, as hot-dip galvanizing is dozens of times better than cold-dip galvanizing.
2. The way of operation is different: hot-dip galvanizing is zinc plated in a molten zinc solution at 450-480 degrees, while cold-dip galvanizing 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 greater than that of cold-dip galvanizing.
4、Surface smoothness is different, cold galvanized appearance is smoother and better than hot galvanized.
5、Price is different, the price of hot dip galvanizing is higher than cold dip galvanizing.
6、Cold galvanizing can be plated on one side only, while hot galvanizing has to be fully plated.
7, adhesion is different, cold galvanizing adhesion is not as good as hot dip galvanizing.
8. The charges are different. Hot-dip galvanizing is charged according to the thickness of the material, while cold-dip galvanizing is mostly charged according to square meters.
Hot-dip galvanizing process is mainly used in the following fields: industry, construction, electric power facilities, chemical facilities, machinery manufacturing, petroleum, municipal facilities, agricultural facilities, communication facilities, fire-fighting facilities, railroad and highway transportation facilities, etc.
Product Types
Galvanized products can be divided into galvanized sheets and coils and galvanized structural parts. There are numerous products in galvanized structural parts. It contains galvanized structural steel, galvanized pipes and galvanized hardware.
Galvanized sheet
Galvanized sheet is a steel plate with a layer of zinc plated on its surface. It is a metal zinc coated on the surface of the steel plate to prevent the surface of the steel plate from corrosion to extend its service life, and this zinc coated steel plate is called galvanized sheet.
The end consumption of galvanized sheet is mainly in the construction, automobile and home appliance fields, with the construction field accounting for the largest share of 45%.
The main exporters of galvanized sheet are Korea, Thailand, Vietnam, Philippines, Belgium, Italy, Japan, Myanmar, Brazil, Israel, Russia, Indonesia, Peru, Bugeti, and Chile, accounting for more than half of the total export volume.
Galvanized structural parts
Galvanized structural parts are mainly divided into three aspects: galvanized structural steel, galvanized pipes and galvanized hardware, among which galvanized structural steel includes guardrails, accessories and steel structures. Guardrails are mainly used in traffic; accessories are mainly used in electrical appliances, automobiles, mechanical equipment, etc.; steel structures are mainly used in construction steel structures and public implementation steel structures.
The end consumption of galvanized structural parts is mainly in infrastructure (including electric power), transportation, construction, etc., with the largest proportion in the construction field, 40%; infrastructure (including electric power) field is 35%.
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