The hot-dip galvanized pipe melts the molten metal and the iron alloy layer, so that the substrate and the coating are mutually inductive. Hot-dip galvanizing is to immerse the steel pipe in acid. In order to remove the iron oxide on the surface of the steel pipe, after the steel pipe is pickled, it is mixed with an aqueous solution of ammonium chloride or zinc chloride or ammonium chloride and zinc chloride, and then put into the hot-dip galvanizing Slot. The hot-dip galvanized coating is well-proportioned, with strong adhesion and long application life. The matrix of the hot-dip galvanized steel pipe and the molten bath undergo a complex physical and chemical reaction to form a densely laid out corrosion-resistant zinc-iron alloy layer. The alloy layer is fused with the pure zinc layer and the steel pipe matrix, so its corrosion resistance is exceptionally strong.