Hot galvanizing is to make molten metal react with iron substrate to produce alloy layer, so that the substrate and the two layers of coating are combined. The manufacture of the hot-dip galvanized pipe is to wash the steel tube first to remove the iron oxide on the surface of the steel tube. After pickling, it is cleaned by the solution of ammonium chloride or zinc chloride or ammonium chloride and zinc chloride and then into the hot dip bath.
Hot-dip galvanized steel tube is a kind of zinc-iron alloy layer with close corrosion resistance, which is formed by complex physical and chemical reactions between the steel tube substrate and the molten bath. The alloy layer is integrated with pure zinc layer and steel tube substrate, so the hot-dip galvanized steel tube has the advantages of uniform coating, strong adhesion and long service life.