Seamless tubes are produced by causing the molten metal to react with the iron substrate, creating an alloy layer that bonds the base and coated layers together. Hot-dip galvanizing involves first pickling steel pipes to remove surface oxide iron, followed by cleaning in an ammonium chloride or zinc chloride aqueous solution or a mixture of both in a槽. The hot-dip galvanized coating offers uniformity, strong adhesion, and a long service life.