When steel pipes are coated with a solvent aqueous solution and then dried, if they are not heated to the required drying temperature for hot-dip galvanizing and contain excessive moisture, they are considered inadequately dried. The consequences of inadequate drying can lead to several issues:
(1) Inadequate drying fails to fully expel hydrogen gas generated during the acid pickling of the steel pipe's metal substrate, affecting the quality of the galvanized coating.
(2) It causes unnecessary corrosion of the steel pipe's metal substrate, resulting in the formation of iron chloride, which increases zinc consumption and roughens the galvanized coating.
(3) The aluminum component in the zinc bath undergoes intense oxidation due to moisture, producing a significant amount of aluminum oxide (Al₂O₃), wasting aluminum and accelerating solvent aging.
(4) When moisture encounters hot zinc liquid, it rapidly turns into water vapor, hydrogen, and oxygen, causing the zinc liquid inside the steel pipe to eject violently from exposed holes, posing a danger, wasting zinc, and creating uncoated spots.
(5) Water vapor produced when moisture encounters zinc liquid strongly oxidizes zinc at 350°C. Since the zinc bath itself operates within a temperature range of 470-500°C, the oxidation is even more intense, increasing zinc consumption and resulting in inferior galvanized coating quality.
