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Hot Galvanizing is an effective metal corrosion protection method used primarily in metal structures in various industries. The rust-removed steel is immersed in a zinc solution melted at about 500 ° C to adhere the zinc layer to the surface of the steel member, thereby preserving the corrosion. It is developed from the older hot-dip galvanized method. Since 1836 France applied hot galvanized to industry, it has been one hundred and forty years old. However, the hot dip galvanized industry has developed rapidly over the past thirty years with the rapid development of cold rolled strip.
Pretreatment before Galvanized
The surface pretreatment work is mainly pickling and water washing and drying which means that the oxide on the original steel sheet is dissolved by pickling to prevent the zinc layer from being attached during further galvanizing.
The pickling process is very important. The short-term adhesion of the zinc layer due to poor pickling can cause the zinc layer to fall off during long-term use, thereby greatly reducing the service life of the steel sheet. Supereol's pickling line is equipped with professional pickling inspectors, and each qualified pickled steel plate can enter the next galvanizing process.
Hot dipped Galvanizing
The hot-dip galvanizing layer formation process is a process of forming an iron-zinc alloy between the iron matrix and the outermost pure zinc layer, and the surface of the workpiece forms an iron-zinc alloy layer during hot dip plating, so that the iron and the pure zinc layer are very For a good combination, the process can be simply described as: when the iron workpiece is immersed in the molten zinc liquid, a zinc and an alpha iron (body center) solid solution are first formed at the interface. This is a crystal formed by the dissolution of zinc atoms in the solid state of the base metal iron. The fusion between the two metal atoms is relatively small. Therefore, when zinc is saturated in the solid solution, the two elements of zinc and iron diffuse into each other, and the zinc atoms diffused into (or infiltrated into) the iron matrix migrate in the matrix lattice, gradually forming an alloy with iron, and diffusing. The iron in the molten zinc solution forms an intermetallic compound FeZn13 with zinc and sinks into the bottom of the hot-dip galvanizing pot, which is zinc dross. When the workpiece is removed from the zinc immersion liquid, a pure zinc layer is formed on the surface, which is a hexagonal crystal. Its iron content is not more than 0.003%.
Galvanized Passivation treatment and Inspection
When the parts need to be stored and transported for a long time, passivation should be performed between them to prevent corrosion during storage and transportation. The corrosion product is often referred to as white rust. The passivation methods we use are chromate and phosphate.
1. Smooth appearance, no zinc tumor, burr, silver white.
2. The thickness is controllable and can be selected within 5-107 m.
3. No hydrogen embrittlement and no temperature hazards. It can ensure that the mechanical properties of materials remain unchanged.
4. It can replace the part of hot dipped galvanizing process.
5. Good corrosion resistance, neutral salt spray test for 240 hours.
Zinc is soluble in acid and soluble in alkali, so it is called amphoteric metal. Zinc does not change almost in the dry air. In moist air, zinc carbonate is formed on the surface
of zinc. In the atmosphere containing sulfur dioxide, hydrogen sulfide and marine atmosphere, the corrosion resistance of zinc is poor, especially in the atmosphere of high temperature and high humidity containing organic
acid, and the zinc coating is easily corroded.
Zinc coating is passivated, dyed or coated with light retaining agent, which can significantly
improve its protective and decorative properties. In recent years, with the development of galvanization technology, the usage of high performance zinc plating brighteners has been put into protective decorative applications from simple protective purposes.
Package & Loading
It is mainly used in building, light industry, automobile, agriculture, animal husbandry, fishery and business.
1. Buildings constructions: roofing, ceilings, gutters, venting lines, indoor decorations,
2. Electrical appliances: computer shells, washing machines, refrigerators, dehumidifiers, video recorders, water heaters, etc.
3. Agricultural equipments: troughs, feeding tools, agricultural driers,
irrigation channels, etc.
4. Vehicle parts: back-seat plates of buses and trucks, conveying systems, oil tanks, etc.