1 the introduction
Hot 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 power transmission, transportation and communications, the protection requirements for steel parts are getting higher and higher.
2. Protective property of hot galvanizing layer, usually the thickness of electric galvanizing layer is 5~15um, while the hot galvanizing layer is generally over 35um, even up to 2001m.The coating capability of hot galvanizing is good, the coating is compact, no organic matter inclusion.As is known to all, the anti-atmosphere and corrosion mechanism of zinc have mechanical protection and electrochemical protection. Under atmospheric corrosion conditions, Zn0, Zn.When the zn layer is seriously damaged and the iron matrix is endangered, zn is produced to the substrate, electrochemical protection, standard potential of zn -0.76V, standard potential of iron -0.44V. When zn and iron form microcells, zn is dissolved as anode, and iron is protected as cathode.It is obvious that the resistance of hot galvanizing to atmospheric corrosion of matrix metal iron is better than that of electric galvanizing.
3.Forming process of hot galvanizing layer
Galvanized layer formation process is the most out of pure iron substrate and formed between the zinc layer of iron, zinc alloy, the process of workpiece surface formed in hot dip plating of iron - zinc alloy layer, and 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, in the first place on the interface formation of zinc iron heart (body) with a solid solution.This is a crystal formed by a matrix metal iron in a solid state dissolved by zinc atoms. The two metal atoms are fused with each other.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, a pure zinc layer is formed on the surface, which is a hexagon crystal.Its iron content should not exceed 0.003%.