There are several different processes for galvanizing steel:
The first and foremost method for galvanization is hot-dip galvanizing.
In this method, steel or iron is dipped in a molten pool of zinc that maintains a temperature of around 460 °C. This molten bath begins a metallurgical bond between the zinc and the receiving metal.
After the metal is pulled from the bath, the pure zinc mixes with oxygen from the atmosphere to form zinc oxide. The zinc-oxide further reacts to carbon dioxide and forms zinc carbonate, which makes up the final protective coating on the material.
The hot-dipped galvanizing method is an economical choice that can be quickly executed on both simple and complex shapes.
Galvannealing is the process of combining the annealing and hot-dip galvanizing processes in order to produce a specialised coating on steel.
Galvannealed steel is a zinc-iron alloy product, where the base metal is coated by the hot-dip process, then heated to induce alloying between the molten zinc coating and the steel. The resulting finish is a dull matte surface.
Galvannealed steel is conducive to welding and the surface is excellent for paint adhesion.
Also similar to the hot-dip galvanizing method, but performed at the very first stage of production. Pre-galvanizing is a process that involves rolling the sheet metal through a cleaning agent to quickly prime material for galvanizing. Then, the metal is passed through a pool of molten liquid zinc and is immediately recoiled. The primary advantage of this method is that coils of steel sheet can be rapidly galvanized on a large scale with a more unified coating than the traditional hot-dipped method.
During the electrogalvanizing process an electric current is introduced to an electrolyte solution that is applied to the steel. This reduces positively charged zinc ions to zinc metal – which is then deposited on the positively charged steel. Like pre-galvanizing, this method is typically done at the first stage of production.