Hot dip galvanizing is a process of coating of steel with molten zinc to protect the steel from rusting and oxidation. It is a process that has been done for the last 170 years and it can be done simply by dipping the steel parts in HCl; hydrochloric acid, and then dipping them in molten zinc. When the surface is free from oxides, the steel can react with the zinc and the galvanized coating forms. EVERY STEP YOU ADD TO THIS HCl-MOLTEN ZINC CYCLE, YOU ACHIEVE A HIGHER QUALITY AND A LOWER ZINC CONSUMPTION.
The structure of Galvanized Coatings
Galvanized coating consists of 2 main layers, iron-zinc alloy layer which is close to the steel surface and the pure zinc layer at the top.
Hot Dip Galvanizing Process
The iron-zinc layer is harder and less elastic. In corrosion protection, it is the same as pure zinc layer.
When we look closely to the iron-zinc layer, the alloy layer also consists of 3 different layers; Gamma layer which is closer to the steel substrate with around 25% iron, Delta layer with 10% iron, Zeta layer which has around 6% iron, Eta layer, with pure zinc.
During galvanizing, in the first half-minute the iron zinc layers forms.
The formation of these layers is related with:
- The composition of the steel,
- Temperature of the zinc bath,
- The quenching operation after the galvanizing.
Being harder than the steel substrate, Gamma, Delta and Zeta layers provide exceptional protection against coating damage through abrasion. The Eta layer is very elastic, which gives an impact resistance to galvanizing. With the metallurgic reaction between the iron and zinc, galvanized coating is adherent to the steel.
These three properties, hardness, ductility and adherence make the galvanized coating a versatile coating with combined protection for corrosion and damage in rough handling conditions during transportation and service.
As Anı Metal, with the experience and knowledge of our staff, we provide an unlimited and free consultancy and engineering service to our customers, to let them achieve minimum process cost and high quality and high efficiency in hot dip galvanizing.