Hot-dip galvanizing is a method of immersing metal in a molten zinc bath so that zinc forms a protective film on the metal surface. This process can be carried out at room temperature, but for best results it is usually carried out at a temperature of 500-600°C. The advantage of hot-dip galvanizing is that it provides very reliable protection against corrosion, and this protection lasts for a long time. In addition, since hot-dip galvanizing is a thick coating, it can also provide good wear resistance.
Electrogalvanizing, commonly known as cold galvanizing, is a method of immersing metal in a molten zinc bath to form a protective film on the metal surface. It uses an electrochemical method, using a zinc ingot as an anode and zinc atoms. After losing electrons, they become ions and dissolve into the electrolyte. The steel strip serves as the cathode. Zinc ions gain electrons from the steel strip and are reduced to zinc atoms, which are deposited on the surface of the steel strip to form a coating.
There is a big difference in the amount of galvanizing between hot-dip galvanized sheets and electro-galvanized sheets. The galvanizing amount of hot-dip galvanizing cannot be too small. Generally, the minimum is 50~60g/m2 on both sides and the maximum is 600g/m2. The galvanized layer of electro-galvanized sheets can be very thin, with a minimum of 15g/m2. However, if the coating is required to be thicker, the production line speed will be very slow, which is not suitable for the process characteristics of modern units. Generally, the maximum is about 100g/m2. Because of this, the production of electro-galvanized sheets is greatly restricted.
