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The thickness of the galvanized layer is usually 5-15 μ m, while the hot-dip galvanized layer is generally above 35 μ m, and even up to 200 μ m. Hot dip galvanizing has good coverage ability, dense coating, and no organic impurities. As is well known, the mechanism of zinc's resistance to atmospheric corrosion includes mechanical protection and electrochemical protection. Under atmospheric corrosion conditions, the surface of the zinc layer has a protective film of ZnO, Zn (OH) 2, and basic zinc carbonate, which can slow down the corrosion of zinc to a certain extent. When this protective film (also known as white rust) is damaged, a new film layer will be formed. When the zinc layer is severely damaged and endangers the iron substrate, zinc provides electrochemical protection to 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 microbattery, zinc is dissolved as the anode and iron is protected as the cathode. Obviously, hot-dip galvanizing has better resistance to atmospheric corrosion than electroplating galvanizing on the base metal iron.