Hot dip galvanizing is a process of coating the assembled steel by immersing the assembled steel in a molten zinc bath. The hot-dip galvanizing process consists of three basic steps; surface preparation, galvanizing and inspection
BENEFITS
When the finished steel reaches the galvanizing equipment, it can be suspended or placed in a racking system with steel wires, and then lifted and moved by an overhead crane. Then, the steel goes through a series of three cleaning steps. Degreasing, pickling and flux. Degreasing removes dirt, grease and organic residues, while the pickling tank will remove oxide scale and iron oxide. The final surface preparation step, flux, will remove all residual oxides and apply a protective layer on the steel to prevent further oxide formation before galvanizing. The correct surface treatment is critical, because zinc does not react with dirty steel.
After surface treatment, the steel is immersed in a molten bath of at least 98% zinc. The steel descends into the pot at an angle that allows air to escape from the tubular shape or other bag, while the zinc flows in, flowing through the entire workpiece. When immersed in the pot, the iron and zinc in the steel undergo a metallurgical reaction to form a series of zinc-iron intermetallic layers and pure zinc outer layers.
The last step is to check the coating. The quality of the coating can be determined very accurately by visual inspection, because zinc will not react with dirty steel, which will leave uncoated areas on the part. In addition, a magnetic thickness gauge can be used to verify whether the coating thickness meets the specifications.