Galvanizing coating is a process in which coating of zinc placed to prevent the base metal. it provides the layer that protect the steel from corrosive attacks.
Galvanizing coating process found more suitable and tough in the aggressives environments. continuous galvanizing process is done in various steps.
The process includes:
- annealing from furnace
- zinc coating
Galvanizing coating process begins with the cleaning of coil .it is done by de greasing process .this process contains alkaline liquid combined with brushing, rinsing and drying.
After this process the coil enters to the furnace for annealing process. in this coil is passed through various section which contains compostion of hydrogen and nitrogen to remove any oxide on the surface of coil.
At the exit of coil from the furnace , coil pass through snout. After this coil is immersed in the molten zinc pot where coating of coil takes place at particular temperature.
As the coil is withdrawn from the pot, high pressure knives is used to remove excess amount of zinc to control coating thickness. for better quality zinc pot composition analysis is done.
To achieve flatness and required elongation coil passed through skin pass mill or tension leveler line.
At the end chrome coating is done to prevent coil from white rust .
Mainly in various industries the annealing process of continuous galvanizing line is done by Non-ox furnace.
This furnace includes various section:
Firstly the coil passed though PHF(PREHEATING FURNACE). In this burners are placed to provide fixed air gas ratio to enable an oxidizing atmosphere in the first zones .
Then the coil pass through RTF (RADIANT TUBE FURNACE).In this electrical heaters are placed that provide particular temperature to the coil. it contains annealing temperature in the presence of protective atmosphere of nitrogen and hydrogen. the temperature range between 550-750 deg celsius.
The coil is then go through soaking point to achieve desired properties. before entering the zinc pot
JCF(JET COOLING FAN) brings down the temperature of coil through cooling fan. at the end coil enters the zinc pot and zinc coating takes place.
Today many steels users and manufacturers automobiles and appliance inclined towards coated products.
Advantages of galvanizing
- long life
- toughest coating
- fully protection
- ease of inspection.
Galvanizing inhibits the corrosion of steel. Especially in marine areas.