Hot-dip seamless tubes are produced by causing the molten metal to react with the iron base to form an alloy layer, thereby combining the base and plated layers. Hot-dip galvanizing involves first pickling steel pipes to remove surface oxide iron, then cleaning them in an ammonium chloride or zinc chloride aqueous solution or a mixture of both, and finally dipping them into a hot-dip galvanizing tank. Hot-dip galvanizing offers advantages such as even coating, strong adhesion, and a long service life.