What is Hot-Dip Galvanizing?

The hot-dipped galvanizing refers to the metal surface treatment. The metal product will be immersed it in the bath of the molten zinc. The whole process of the hot-dipped galvanizing process can be divided into 3 parts, like the surface preparation, galvanizing, and inspection.

1. Surface Preparation

When the metal panel are ready to be galvanized, it will be hung by the solid wire or be placed on the shelters, with the help of the overhead cranes, the metal product and the carrying system can be lifted and moved through. The steel then goes through a series of three cleaning steps; degreasing, pickling, and fluxing.

Degreasing removes dirt, oil and organic residues, while the acid bath will remove mill scale and iron oxide. In the last surface preparation step, the fluxing, it will remove the remaining oxides and coat the metal with the special protective layer to prevent any further oxide formation prior to galvanizing. Proper surface preparation is critical, as zinc will not react with unclean steel.

2. Galvanizing

After the surface preparation, the metal product will be bathed in the molten zinc, which the purity can reach at least 98%. The metal will be bathed into the tank at the special angel, which allows the zinc covered the whole object without any left space. While bathed in the zinc, the iron will react with the zinc to form a series of zinc-iron intermetallic layers and an outer layer of pure zinc.

3. Inspection

The final step will be quality test of the coating. The zinc will not react with the unclean steel, which would leave an uncoated area on the part. This would be the most simple way to test the coating layer by the visual inspection. Additionally, a magnetic thickness gauge can be used to verify the coating thickness complies with specification requirements.