Difference between hot-dip galvanized pipe and cold galvanized pipe

Hot-dip galvanized pipe

Hot dip galvanized pipe is the reaction of molten metal with iron matrix to produce alloy layer, so that the matrix and the coating are combined. Hot dip galvanizing is to first pickling the steel pipe, in order to remove the iron oxide on the surface of the steel pipe, after pickling, through ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tank for cleaning, and then into the hot dip plating tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The matrix of hot dip galvanized steel pipe and the molten bath undergo complex physical and chemical reactions to form a tight zinc-iron alloy layer with corrosion resistance. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix, so its corrosion resistance is strong.

Cold galvanized pipe

Cold galvanized pipe is electric galvanized, galvanized amount is very small, only 10-50g/m2, its own corrosion resistance is much different than hot galvanized pipe. Regular galvanized pipe manufacturers, in order to ensure quality, most do not use electric galvanizing (cold plating). Only those small enterprises with obsolete equipment use electric galvanizing, of course, their prices are relatively cheap. The Ministry of Construction has formally announced the elimination of cold galvanized pipes with backward technology, and it is not allowed to use cold galvanized pipes as water and gas pipes. The galvanized layer of cold galvanized steel pipe is an electric coating, and the zinc layer is independently layered with the steel pipe matrix. The zinc layer is thin, and the zinc layer is simply attached to the steel tube matrix and easy to fall off. Therefore, its corrosion resistance is poor. In new residential buildings, it is prohibited to use cold galvanized steel pipes as water supply pipes.