Production process of hot-dip galvanized steel coil
The primary method of producing galvanized steel coils is through the hot dip galvanizing process. This process involves several important steps. Firstly, the steel undergoes a cleaning process, which consists of three stages: degreasing, pickling, and fluxing. Degreasing removes any organic residues, such as dirt and oil, from the steel surface. Pickling uses a mild acid bath to etch the steel and remove any mill scale and iron oxide. Fluxing then removes any remaining oxides and coats the steel with a protective layer to prevent the formation of additional oxides on the steel surface prior to galvanizing.
After the steel has been cleaned and dried, it is ready to be immersed in a molten zinc bath. This process involves coating an iron or steel object by immersing it in a molten zinc bath at temperatures of around 840°F (449°C). During this stage, the molten zinc spangles around the iron or steel object, thoroughly coating it to protect all surfaces.
Once removed from the bath, the zinc coating on the iron or steel’s exterior reacts with oxygen in the atmosphere to form zinc oxide (ZnO).
Zinc oxide then further reacts with carbon dioxide to form the protective layer known as zinc carbonate (ZnCO3). This dull grayish film is relatively stable and adheres tightly to the surface of the iron or steel. In the hot dip galvanizing process, the zinc chemically bonds and becomes a part of the steel, thus providing protection against corrosion.