After being uncoiled, the steel strip is first treated at the pre-treatment tank including degreasing, pickling, and cleansing. This process is designed to smooth the surface and increase adhesion of zinc during the plating process.
ANNEALING AND PLATING
Annealing is the next process. In the annealing furnace, heat cycle is applied to obtain the required mechanical properties and activate the surface with a reducing gas, which makes it easy to coat zinc on the strip surface.
After that, Zinc plating is done through a zinc pot after annealing process in order to secure processability and the quality of the material of the final product. The amount of plating shall be adjusted to the customer request by air blowing (air knife) located above the pot.
After plating, the strip is still hot and will be cooled through cooling system and water tank to decrease the temperature of strip down to 600oC – 800oC; moreover, clean up all the mixture of salt, zinc dust, and other impurities in order to keep the surface always clean before going through the next process.
The steel strip will be dried up by a pair of rubber rollers after go through water tank, then continue to be immersed in a chromic (Cr) bath. This process will help increasing rust resistance for the surface and against weather impact.