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  What is Hot Dip Galvanized (HDG)?


Hot galvanizing is the most effective system to protect iron and steel from the corrosion that these materials experience when exposed to the atmosphere, water and soil.


It consists in the formation of a zinc coating on the pieces of iron or steel by immersing them in a bath of molten zinc at 450ºC.


The galvanization reaction only occurs if the surfaces of the materials are chemically clean, so they must be previously subjected to a surface preparation process.


During the immersion in molten zinc, a diffusion reaction between zinc and steel occurs, which results in the formation of different layers of zinc-iron alloys. When extracting the materials from the zinc bath, these layers of alloy are covered by an outer layer of pure zinc. The result is a zinc coating metallurgically bonded to the base steel by different layers of zinc-iron alloys.




  The coatings that are obtained by hot galvanization are constituted by several layers of zinc-iron alloys, basically three, which are called "gamma", "delta" and "zeta" and an outer layer of practically pure zinc (phase "eta" ), which is formed by solidifying the zinc dragged from the bath and which gives the coating its characteristic bright metallic gray appearance.



Being coatings obtained by immersion in molten zinc, they cover the entire surface of the pieces, both the exterior and interior parts of the hollow parts as well as many other surface areas of the pieces that are not accessible for other protection methods.  


Abrasion resistance 


Galvanized coatings have the almost unique feature of being metallurgically bonded to the base steel, so they have excellent adhesion. On the other hand, being made up of several layers of zinc-iron alloys, harder even than steel, and an outer layer of zinc that is softer, they form a system that is very resistant to shock and abrasion.  

Hardness diagram of galvanized coatings 



Thickness comparison

Hot galvanizing is the only corrosion protection system that is alloyed with the base metal, in addition to greatly exceeding the thickness of the coating in comparison with the other methods.

Download our brochure with more detailed information about hot dip galvanizing here.


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