Hot dip galvanizing: hot dip galvanizing is that put the steel components into the about 600 ℃ high temperature melting of zinc solution after blast cleaning , attached layer of zinc to the steel component surface, thickness of zinc is not less than 65μm about the thin plate bellow 5mm, the thick plate not less than 86μm. Thus play a corrosion purposes. This method has the advantage of long life durability, high industrialization production and stable quality. They have been used extensively for serious corrosion by the atmospheric and difficult to repair the outdoor steel structure. Such as large transmission towers, communication tower. In recent years large numbers pressure plate of light steel structure system and so on also use the dip galvanizing. The first procedure is rust, then wash. The two procedures

must be completely if will leave hidden corrosion.It must be addressed thoroughly. For the steel structure designers, design should be avoided with relative fitting surface of the component, in order to avoid cracks in the surface fit is not complete or pickling acid wash clean. caused the phenomenon flowing fellow water of Galvanized surface. Hot-dip zinc is carried out at high temperatures. The ends of tubular members should be allowed to open. The closure both ends will cause the air expansion so tube burst, resulting in accidents. If zinc closed at one end the fluid flow is poor and easy to accumulate in the pipe.