Galvanized sheets are produced by hot-dip method. The advantage of this method over the other methods is its cost-effectiveness, possibility of high thicknesses of coating, high strength and bonding of galvanized coating to the base metal.
The incoming coils from cold-rolling mill (tandem mill and 2-stand rolling mill), are welded together at the entry of the galvanizing line to form a continuous strip to be fed to the galvanizing line. The sheet is degreased in alkaline materials, brushed, and cleansed in hot water and dried in a stream of hot air.
The coils so cleaned enter the annealing furnaces with a protective atmosphere of inert gases. In the three steps of preheating, heating and soaking (even distribution of heat over the coil) depending on the application of the annealed product, the coil is cooled down by the cooling system whereby its temperature is adjusted for the entrance into the liquid zinc bath. The sheet will have two thin layers of liquid zinc upon the exit from the galvanizing bath.
An air jet adjusts the thickness of the coating of the liquid zinc immediately after the sheet gets out of the molten zinc. The sheet is blown with air in order to cool down, and enters the cold water tank. In the end, the sheet is dried in a stream of hot air blown onto it.
It is noteworthy that in this process, the thickness of the coil is monitored by the thickness gauge and is given the desired fine or coarse surface by the skin-pass and sheet correction equipment.
In order to prevent the sheets from white rusting while in store, they are chromated and the galvanized surface is passivated.
After the inspection, in case there is a customer order, a protective oil layer is sprayed on the surface of the sheet by the electrostatic oiling unit. The galvanized coil thus produced is packaged and sent to the consuming market.
Main applications of the galvanized sheets:
Electrical panels and cabinets, cable trays
Some of the home appliances parts and kitchenware
Air ducts, chimneys, rainwater drainpipes, and pipes