Zinc is easily soluble in both acids and alkalis, earning it the name of an amphoteric metal. Zinc undergoes little change in dry air but forms a dense layer of basic zinc carbonate on its surface in humid air. In environments containing sulfur dioxide, hydrogen sulfide, and marine atmospheres, zinc exhibits poor corrosion resistance, especially in high-temperature, high-humidity environments containing organic acids, where zinc coatings are highly susceptible to corrosion.
Hot-dip galvanized pipes are produced by reacting molten metal with an iron substrate to form an alloy layer, thereby integrating the substrate and the coating. The production process of hot-dip galvanized pipes begins with pickling the steel pipes to remove iron oxide from their surfaces. After pickling, the pipes are cleaned in a tank containing an aqueous solution of ammonium chloride, zinc chloride, or a mixture of both, and then sent into a hot-dip galvanizing bath. Hot-dip galvanizing offers advantages such as uniform coating, strong adhesion, and long service life. In northern regions, a direct zinc-coated strip rolling and zinc replenishing process is commonly adopted.
Hot-dip galvanized steel pipes undergo complex physical and chemical reactions between the steel pipe substrate and the molten galvanizing solution, resulting in the formation of a corrosion-resistant, structurally dense zinc-iron alloy layer. This alloy layer merges seamlessly with the pure zinc layer and the steel pipe substrate, imparting exceptional corrosion resistance.
To enhance the corrosion resistance of steel pipes, they are galvanized, with two primary methods: hot-dip galvanizing and electroplating. Hot-dip galvanizing results in a thicker zinc coating, while electroplating is cost-effective but may yield a less smooth surface. Oxygen-blown welded pipes, typically small-diameter welded steel pipes ranging in size from 3/8 to 2 inches, are used for steelmaking oxygen blowing. Made from steel strips such as 08, 10, 15, 20, or 195-Q235 grades, some pipes undergo effective aluminizing treatment for corrosion prevention.
Production Process:
Galvanized strip → Uncoiling → Stretching → Rolling into pipe → Welding → Scar removal → Passivation and rinsing → Zinc replenishing → Sizing → Typing and labeling → Cutting → Packaging → Drying → Weighing.
