Galvanized Steel

Surface Preparation

The initial phase of hot-dip galvanizing is critical for ensuring a high-quality finish. Steel bars are suspended by wire or placed in a racking system, then lifted and transported through the process by overhead cranes. The steel undergoes three essential cleaning steps: degreasing, pickling, and fluxing. Degreasing removes dirt, oil, and organic residues while pickling eliminates mill scale and iron oxide using an acidic bath. Finally, fluxing removes any remaining oxides and coats the steel with a protective layer to prevent further oxidation before galvanizing. Proper surface preparation is vital, as zinc will not adhere to unclean steel.

Galvanizing

Following surface preparation, the steel is submerged in a molten zinc bath heated to approximately 830°F. The steel is lowered into the kettle at an angle, allowing air to escape and ensuring the zinc flows over and through the entire piece. During immersion, the iron in the steel reacts metallurgically with the zinc, forming a series of zinc-iron intermetallic layers and an outer layer of pure zinc. This process conforms to several standards, including IS:209 for zinc grade, IS:2633 for elcometer readings, IS:2629 for deep testing, and IS:4759 & 6745 for zinc coating mass requirements. The standard zinc coating requirement is 610gm/m2, with elcometer testing results showing a thickness of 86 to 120 microns at temperatures between 428°C and 465°C.

Inspection

The final step in the galvanizing process is a thorough inspection of the coating through a magnetic thickness gauge that verifies the thickness microns of the coating, ensuring the highest quality of galvanized steel. A Material test certificate is then prepared and sent along with the material.