Hot-dip galvanizing (HDG) is the process of dipping fabricated steel into a kettle or vat containing molten zinc. The process is inherently simple which provides a distinct advantage over other corrosion protection methods. While the steel is in the kettle, the iron in the steel metallurgically reacts with the molten zinc to form a tightly-bonded alloy coating that provides superior corrosion protection to steel.
Hot dip galvanizing is the leading method which protect the prepared metal and steel structures from atmospheric, water and soil corrosion.
Every year the world produced millions tons of zinc. Half of this is used to protect steel from rust. Also using other metals, including magnesium, aluminum, cadmium.
Coating thickness is 60 -100 microns (depending on the thickness and chemical composition of steel from which the product is manufactured). Zinc cladding is a barrier which protects the surface from the environment. However, except barrier, zinc also provides electrochemical protection, because the osculation with iron galvanic cell is formed. Other anti-corrosion system or create a protective barrier or galvanic cell. Only hot-dip galvanizing combines these two methods into one, creating an effective method that protects steel for many years. The service life of galvanized metal is from 20 to 65 years depending on the thickness of the coating and the aggressiveness of the environment.
The process consists of 6 stages:
1. Degreasing – at this stage, carry out the removal of metal surfaces and structures of fatty stains, preservative oils and other synthetic layers that prevent and slow down the digestion process.
2. Digestion – is an important stage in surface preparation for galvanizing metal. On this stage is removed from the surface details of the rust and chemical activation of the surface of steel without damage to the main surface.
3. Flushing – on this stage is flushing digestion products from the surface that are prepared to galvanizing.
4. Fluxing – the final stage of surface preparation that it is necessary to cover the surface layer of salt to ensure optimal adhesion. Besides a flake of flux is protective.
5. Drying – the process of drying is drying salt flux. Products heat up to 100 º C.
6. Galvanizing – the formation of zinc coating as a result of reaction between iron and molten zinc.
Each of these processes takes place in special vat.
Hot dip galvanizing services include:
- Chemical preparation of the surface;
- Applying a zinc coating in accordance with ISO 1461:2009;
- Cleaning products after hot-dip galvanizing process.