The classification of the galvanized steel

Hot dip galvanized steel 
Hot dip galvanized pipe is to make molten metal react with iron matrix to produce alloy layer, so as to combine the matrix and coating. Hot dip galvanizing is to pickle the steel pipe first. In order to remove iron oxide on the surface of the steel pipe, after pickling, it is cleaned in ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tank, and then sent to the hot dip galvanizing tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The matrix of hot-dip galvanized steel pipe has complex physical and chemical reactions with the molten plating solution to form a corrosion-resistant zinc ferroalloy layer with compact structure. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix. Therefore, it has strong corrosion resistance.

Cold galvanized steel

Cold galvanized pipe is electro galvanized. The amount of galvanized is very small, only 10-50g / m2. Its corrosion resistance is much different from that of hot-dip galvanized pipe. Regular galvanized pipe manufacturers, in order to ensure quality, Most of them do not use electro galvanizing (cold plating). Only those small enterprises with small scale and outdated equipment adopt electro galvanizing. Of course, their price is relatively cheap. At present, the Ministry of construction has officially eliminated the cold galvanized pipe with backward technology, and it is not allowed to use the cold galvanized pipe as water and gas pipe in the future. The zinc layer of the cold galvanized steel pipe is an electroplating layer, and the zinc layer is separated from the steel pipe matrix. The zinc layer is thin, and the zinc layer is simple to attach It is easy to fall off when it is attached to the steel pipe matrix. Therefore, its corrosion resistance is poor. In new houses, it is forbidden to use cold galvanized steel pipes as water supply pipes.