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What is galvanized?

Oct. 23, 2019

Galvanized, refers to the surface of iron or steel coated with metal zinc rust prevention method. Zinc is a highly corrosion-resistant metal that insulates iron from oxygen and water, preventing the chemical reactions needed to rust. Because zinc is a more active metal than iron, even if the zinc on the plating is damaged, zinc can still be sacrificed to protect the electrochemical way to prevent rust. Galvanized methods mainly include hot dip galvanized (HDG), electric galvanized (EG) and cold galvanized. According to the archaeological findings, as early as the 1680s, people have been galvanized cut wire treatment.

The methods of galvanizing include hot dip galvanizing, hot spray galvanizing, electric galvanizing, cold galvanizing, powder hot dip galvanizing, mechanical galvanizing and vacuum evaporation galvanizing.

Hot dip galvanizing (HDG) is one of the most common methods of galvanizing, which involves the complete immersion of iron or steel in molten zinc. Compared with electric galvanizing, hot dip galvanizing has the advantage of lower cost. Chemical reactions during galvanization occur only on clean iron or steel surfaces. Therefore, before hot dipping, steel and iron materials will be degreased (cleaned with alkaline chemicals), repeatedly washed and pickled to ensure the quality of the finished products. The steel material is then dipped in a plating aid (usually ammonium chloride and zinc chloride) and preheated by drying. After the iron and steel material is processed, the iron and steel material will be immersed in the molten zinc solution (that is, the melted zinc). A series of complex chemical reactions will occur between the iron and zinc. The zinc layer is 6 to 20 microns thick and relatively thick, usually consisting of a pure zinc layer and an alloy layer. The hot dip process includes cooling, passivation, testing, etc. Adding other metals to the molten zinc solution can adjust the properties of the zinc layer: for example, adding aluminum, magnesium, nickel and other metals can improve the corrosion resistance of the zinc layer, adding aluminum, lead, tin, antimony and other metals can optimize the appearance of the zinc layer. On the other hand, carbon, silicon, manganese, phosphorus and sulfur in iron and steel materials will affect the structure and properties of zinc layer. Hot dipped galvanized galfan wire is a common application of hot dip galvanized.

Hot dipped galvanized steel wire

Hot dipped galvanized steel wire

Electro galvanizing (EG) is a kind of electroplating, and its production line is very expensive. Compared with hot-dip galvanizing, the advantage of electro galvanizing is that the zinc coating is more uniform. In the process of electro galvanizing, the iron or steel to be galvanized is the cathode, the zinc to be plated is the anode, and the zinc salt solution is the electrolyte. The zinc layer is 7 microns thick and relatively thin. Electro galvanized steel wire is made in this way.

Cold galvanization is to point to be coated on the surface of iron and steel material rich zinc paint, this method needs the equipment that paints USES normally only, but the durability of zinc layer (call rich zinc coating) and service life are poorer, the sacrificial sex protection that provides to iron and steel material also is less.

Galvanized is a general method of rust prevention, different sizes (such as bolts and other small mechanical parts, to large structural parts) and shapes (such as hollow objects, complex shapes, utensils, etc.) of iron and steel materials can be galvanized. Galvanized iron refers to galvanized iron, widely used in petrochemical industry, telecommunications, power supply, transportation, construction, machinery, agriculture and other fields, plays a key role in daily life, but also in some industries come in handy.

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