Pre-painted Galvanized Steel
Pre-painted galvanized steel, refers to ordinary carbon building steel after galvanizing processing.
It can effectively prevent steel corrosion and rust, thereby prolonging the service life of steel, including electric plating and hot dip galvanizing.
Generally it is used for building exterior walls, such as glass curtain wall, marble curtain wall, aluminium curtain wall as pillars and stress materials, or for outdoor telecommunication tower, highway and other open-air construction.
The classification of pre-painted galvanized steel:
pre-painted galvanized steel sheet/coil, pipe, profile such as(channel, angle etc.), wire.
Here we mainly introduce the processing way of pre-painted galvanized steel pipe.
Hot-dip galvanized steel pipe:
Hot-dip galvanized steel pipe is to make molten metal react with iron matrix to produce alloy layer, so that the matrix and coating can be combined. Hot-dip galvanizing is a process of pickling steel pipes.
In order to remove iron oxide from the surface of steel pipes, after pickling, the pipes are cleaned by ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tank, and then sent into the hot-dip galvanizing tank.
Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. Complex physical and chemical reactions occur between the hot-dip galvanized steel tube matrix and the molten plating solution, resulting in a zinc-iron alloy layer with a close corrosion resistance structure. The alloy layer is integrated with pure zinc layer and steel tube matrix. Therefore, it has strong corrosion resistance.
Cold galvanized pipe
Cold galvanized pipe is galvanized, the amount of galvanized is very small, only 10-50g/m2, its corrosion resistance is much different than hot galvanized pipe.
Normal galvanized pipe manufacturers, in order to ensure quality, mostly do not use galvanized (cold plating). Only small businesses with obsolete equipment use galvanizing, and of course their prices are relatively cheap.
At present, the Ministry of Construction has officially eliminated the backward technology of cold galvanized pipes. In the future, cold galvanized pipes are not allowed to be used as water and gas pipes.
The galvanized layer of cold galvanized steel pipe is an electroplating layer, and the zinc layer is separately stratified with the steel pipe matrix. The zinc layer is thin, and the zinc layer simply adheres to the steel tube matrix, which is easy to fall off. Therefore, its corrosion resistance is poor. Cold galvanized steel pipes are forbidden to be used as water supply pipes in new residential buildings.
The processing way for other products is the similar.
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