Hot dip galvanized pipes are formed by reacting molten metal with an iron substrate to produce an alloy layer, thereby combining the substrate and coating. Hot dip galvanizing is the process of first pickling steel pipes to remove iron oxide from their surface. After pickling, the steel pipes are cleaned in an ammonium chloride or zinc chloride aqueous solution or a mixture of ammonium chloride and zinc chloride aqueous solution, 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 substrate of hot-dip galvanized steel pipes undergoes complex physical and chemical reactions with the molten plating solution, forming a corrosion-resistant and tightly structured zinc iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe substrate, so its corrosion resistance is strong.