Principle and process of hot-dip galvanizing steel grating

Hot-dip galvanizing of steel grating is also called hot-dip galvanizing. It melts zinc ingots at high temperature, puts in some auxiliary materials, and then immerses the steel grating components in the galvanizing tank to make the steel grating components adhere to layer of zinc. The advantages of hot-dip galvanizing are its strong anti-corrosion ability and good adhesion and hardness of the galvanized layer. The weight of steel grating products increases after galvanizing, which is often referred to as the amount of zinc applied.

If the hot-dip galvanizing method is used, the steel grating is degreased, pickled, impregnated, dried, and then immersed in the molten zinc solution for a certain period of time, and then taken out; if the cold-dip galvanizing method is used, the steel grating is used In the electrolysis equipment, the steel grating is degreased and pickled, then placed in a solution composed of zinc salts, and connected to the negative electrode of the electrolysis equipment. Place a zinc plate opposite the workpiece and connect it to the positive electrode of the electrolytic equipment. Turn on the power and use the directional movement of the current from the positive electrode to the negative electrode to deposit a layer of zinc on the workpiece. When passing through the test table, the difference between the galvanized finished product and the : The surface of hot-dip galvanizing is not as delicate and bright as cold-dip galvanizing, but the thickness of the zinc layer is dozens of times that of cold-dip galvanizing, and its anti-corrosion performance is also dozens of times that of electro-galvanizing.

Formation of hot dip galvanized layer The formation process of hot-dip galvanized zinc layer is the process of forming an iron-zinc alloy between the iron matrix and the outermost pure zinc layer. The iron-zinc alloy layer is formed on the surface of the workpiece during hot-dip plating, so that the iron-zinc alloy layer is formed between the iron matrix and the pure zinc layer. Very well combined. When the iron workpiece is immersed in the molten zinc liquid, a solid solution of zinc and α-iron (body-centered) is first formed at the interface. This is a crystal formed by the base metal iron dissolving zinc atoms in the solid state. The two metal atoms There is fusion between them, and the gravitational force between atoms is relatively small. Therefore, when zinc reaches saturation in the solid solution, atoms of zinc and iron diffuse into each other. The zinc atoms that diffuse into the iron matrix migrate in the matrix lattice and gradually form an alloy with iron. The iron diffused into the molten zinc liquid forms an intermetallic compound FeZn13 with zinc, which sinks to the bottom of the hot-dip galvanizing pot and is zinc slag. When the workpiece is removed from the zinc immersion liquid, a pure zinc layer is formed on the surface, which is a hexagonal crystal. . Temperature control

At different temperatures and different holding times, the amount of dissolved iron, that is, the amount of iron loss, is different. When around 500°C, the amount of iron loss increases sharply with heating and holding time, lower or higher than 480~510°C. range, the iron loss increases slowly over time. Therefore, people call 480~510℃ the malignant dissolution zone. In this temperature range, the zinc liquid corrodes the workpiece and zinc pot most seriously. When it exceeds 560℃, the iron loss increases significantly. When it reaches above 660℃, zinc will cause damage to the iron matrix. Due to sexual corrosion, zinc slag will increase sharply and plating cannot be carried out. Therefore, plating is currently mostly carried out in the 430-450°C range.