Hot-dip galvanized pipe is formed by the reaction between molten metal and the iron substrate to produce an alloy layer, thereby combining the substrate and the coating. The process involves first pickling the steel pipe to remove the iron oxide on the surface, followed by cleaning in a solution of ammonium chloride or zinc chloride, or a mixture of both, before being immersed in a hot dip galvanizing bath. Hot-dip galvanizing offers advantages such as even coating, strong adhesion, and a long service life. The steel substrate undergoes complex physical and chemical reactions with the molten coating to form a corrosion-resistant, tightly structured zinc-iron alloy layer. This alloy layer is integrated with the pure zinc layer and the steel pipe substrate, resulting in excellent corrosion resistance.