How is galvanized steel made using molten zinc?

Galvanized steel is produced through a process called hot-dip galvanizing, which creates a protective barrier against corrosion.12

The process involves several key steps:

• Preparation: The steel is first cleaned by pickling it in acid to remove impurities and then treated with a flux, such as zinc-ammonium chloride, to ensure proper adhesion.12
• Immersion: The prepared steel is guided through a bath of molten zinc, typically maintained at approximately 450 °C (840 °F).23
• Bonding: As the steel contacts the liquid zinc, a metallurgical reaction occurs, forming layers of iron-zinc alloy on the surface, which are topped with an outer layer of pure zinc.23
• Refinement: In continuous coating lines, small amounts of aluminum (0.1 to 0.25 percent) are often added to the zinc bath to inhibit the formation of brittle iron-zinc compounds, resulting in a more flexible coating. Excess zinc is removed using gas-knives to control the final thickness of the protective layer.23

This coating provides both a physical barrier and sacrificial protection, where the zinc corrodes preferentially to protect the underlying steel.42