What Is Galvanized Steel Made Of?

Galvanized steel is made by coating the steel in zinc to better resist corrosion. There are three methods of producing galvanized steel. The end-use application and coating thickness required determine which process to use when making galvanized steel.

Batch Galvanizing

This process is used on hardware such as bolts, nuts, nails and screws as well as piping and other steel shapes. The steel is fabricated into a form, cleaned, then immersed in molten zinc.

Continuous Galvanizing

This process is used primarily for steel sheet but also steel wire and strip. As the steel passes through a bath of molten zinc, the start of the next coil is welded onto the end of the previous coil.

Electrogalvanizing

Electrogalvanized coatings of zinc are applied through a continuous plating process. The positively charged anodes attach zinc to negatively charged steel.

Bonding Process

With the two hot-dip methods, the zinc coating reacts with the steel to form three underlying zinc-iron alloy layers and one top layer of pure zinc. Electrogalvanizing deposits pure zinc on the steel.

Coating Thickness

Batch galvanizing produces a thicker coating, while the thickness can be adjusted after continuous galvanizing using air streams. With electrogalvanizing, the thickness of the zinc is controlled by the speed at which the steel is fed through and the amount of electrical charge.

References

• ASM International
• American Iron and Steel Institute
• American Galvanizers Association