Principle and process description of hot galvanizing!
1 the introductionHot dip galvanizing, also known as hot dip galvanizing, is a method for steel components to obtain metal coating by immersed in molten zinc solution. In recent years, with the rapid development of high-voltage transmission, transportation and communications, the protection requirements for steel parts are getting higher and higher.
2. Protective properties of hot-dip galvanized layerGenerally, the thickness of electrogalvanizing layer is 5~15um, while the thickness of hot-galvanizing layer is usually more than 35um, even up to 200um. Atmosphere and corrosion resistance of zinc as is known to all, have a mechanical protection and the mechanism of electrochemical protection, under the condition of atmospheric corrosion of zinc layer surface of Zno, zinc (OH) 2 and alkali carbonate zinc coating, to a certain extent reduce the corrosion of zinc, this layer of protective film (also called white, rust) is damaged and will form a new film in the morning. Destroyed when the zinc layer, endanger the iron matrix, the zinc matrix, and produce electrochemical protection, the standard potential of zinc - 0.76 V, iron the standard potential of 0.44 V, zinc and iron formation micro electric, pool zinc as the anode was dissolved, iron are protected as the cathode. It is obvious that hot galvanizing has great resistance to matrix metal iron, and its gas corrosion ability is better than dry galvanizing.
3. Formation process of hot galvanizing layerHot dip galvanized layer formation process is the most out of pure iron substrate and iron - zinc alloy formed between the zinc layer, the process of workpiece table in iron - zinc alloy layer formed when hot dip plating, makes good combination between iron and pure zinc layer, the process, can be simply described as follows: when the blacksmith a immersed in molten zinc liquid, first in zinc is formed on the interface with a iron heart (body) solid solution. This is the matrix metal iron in the solid state of dissolution of zinc atoms form a crystal, two kinds of gold, is the fusion between atoms, the atom is less gravity. So when zinc in solid solution after reaching saturation, two kinds of zinc iron atom diffusion, spread to (or called infiltration) iron matrix of zinc atom in the lattice matrix, migration, gradually formed and iron alloy, and spread to molten zinc liquid iron and zinc in the formation of intermetallic compounds FeZn13, sank into the hot dip galvanized pot is zinc slag. When the workpiece is removed from the zinc immersion solution, the surface forms pure zinc, the layer is hexagon crystal. Its iron content should not exceed 0.003%.