The formation process of the hot-dip galvanized layer is the process of forming an iron-zinc alloy between the iron substrate and the outer pure zinc layer. The iron-zinc alloy layer is formed on the surface of the workpiece during hot-dip plating, so that the iron and the pure zinc layer are very close. Good combination. The process of large coils of galvanized wire can be simply described as: when an iron workpiece is immersed in molten zinc liquid, a solid solution of zinc and α-iron (body center) is first formed on the interface. This is a crystal formed by dissolving zinc atoms in the base metal iron in a solid state. The two metal atoms are fused, and the attraction between the atoms is relatively small.
Therefore, when zinc reaches saturation in the solid solution, the atoms of zinc and iron diffuse into each other, and the zinc atoms that diffuse into (or penetrate into) the iron matrix migrate in the matrix lattice, gradually form an alloy with iron, and diffuse into The iron in the molten zinc liquid forms an intermetallic compound FeZn13 with zinc, sinks into the bottom of the hot-dip galvanizing pot, and becomes zinc slag. When the workpiece is removed from the zinc dipping solution, a pure zinc layer is formed on the surface, which is a hexagonal crystal, and its iron content is not more than 0.003%.
Hot-dip galvanizing, also known as hot-dip galvanizing, is a method in which steel components are immersed in molten zinc to obtain a metal coating. With the rapid development of high-voltage power transmission, transportation, and communication, the protection requirements for steel parts are getting higher and higher, and the demand for hot-dip galvanizing is also increasing. Usually the thickness of the electro-galvanized layer is 5-15 μm, while the thickness of the large coil galvanized wire layer is generally above 35 μm, even as high as 200 μm. Hot-dip galvanizing has good coverage, dense coating, and no organic inclusions.
As we all know, the mechanism of zinc’s anti-atmospheric corrosion includes mechanical protection and electrochemical protection. Under atmospheric corrosion conditions, there are ZnO, Zn(OH)2 and basic zinc carbonate protective films on the surface of the zinc layer, which slow down the corrosion of zinc to a certain extent. The first layer of protective film (also known as white rust) is damaged, and a new film layer will be formed.
When the zinc layer is severely damaged and endangers the iron substrate, zinc will electrochemically protect the substrate, the standard potential of zinc is -0.76V, and the standard potential of iron is -0.44V. When zinc and iron form a micro battery, zinc is dissolved as an anode, and iron Protected as a cathode. Obviously, hot-dip galvanizing is better than electro-galvanizing in its ability to resist atmospheric corrosion of the base metal iron.
Post time: 14-06-23