The production of galvanized steel coils primarily involves two processes: hot-dip galvanizing and electro-galvanizing. Hot-dip galvanizing entails immersing the steel coil in a bath of molten zinc to form a relatively thick zinc coating, whereas electro-galvanizing deposits a zinc layer onto the surface via electrolysis, resulting in a thinner but more uniform coating. Each process has distinct characteristics and is suited to different applications.
1. Hot-dip galvanizing process (mainstream method)
Galvanized coils are primarily produced using the hot-dip galvanizing process. This involves immersing thin steel sheets into a bath of molten zinc so that a zinc layer adheres to the surface; the continuous galvanizing process-where coiled steel is continuously passed through the zinc bath-is currently the dominant method.
2. Galvannealing process
Another method is the galvannealing process, in which the steel is heated to approximately 500°C immediately after exiting the zinc bath to form a zinc-iron alloy layer. Galvanized coils produced via this method offer excellent paint adhesion and weldability.
3. Electro-galvanizing process
Electro-galvanizing is also used to produce galvanized coils; however, the resulting coating is thinner, and its corrosion resistance is inferior to that of the hot-dip method.
4. Surface treatment methods
Depending on the surface treatment applied, production processes can be further categorized into types such as passivation, oiling, and lacquer sealing. Notably, passivation treatment effectively minimizes rust formation (specifically "white rust") during storage and transport in humid conditions.
