HOT DIP GALVANIZATION (H.D.G.)

Unprotected Steel can be seriously damaged due to such environmental factors as rain & snow, wind, and extreme temperature .Corrosion transforms steel back to its natural state of iron, which is very fragile and can prove to be deadly in structures supporting heavy pressure (e.g. Towers).
The best way to avoid this phenomenon is through a process called "hot dip galvanization".
This process consists of dipping steel in melted zinc at 450° Celsius, temperature at which iron and zinc share great affinity, and allowing an alloy to form where pure zinc prevails to the outside. The final product is a Steel surface protected with a zinc coating.

Due to the difference of electrochemical potential between zinc and steel (cathodic protection), a zinc coating can protect Steel in such a way that vigorous forces, such as cutting, scratching or piercing, are equally protected against corrosion.
What considerably affects the appearance and gauge of galvanization is the contents of alloyable elements that are generally present in steel: carbon, magnesium, and silicon. If the contents of these elements increases, the coating gauge also increases and it becomes matte gray. The greatest effect is produced by silicon in concentrations higher than 0.12%.

Most steels can be galvanized: high-strength steel, low-carbon steel,low-alloy steel, and steels with as much as 0.20% copper content; the most appropriate being low-carbon steels.

A basic guide to hot dip galvanizing (File size: 176 Kb)

	Section through galvanized coating showing pure metal zinc and zinc-iron alloy layers which are the normal coating developments on rimmed or aluminum killed steels.
	Section through galvanized coating on silicon containing steel; Coating is zinc-iron alloy which appears gray.
	Section through brown stained galvanized coating which remains substantially intact under the brown stain. The uncolored material close to the galvanized surface is aluminum sheet used to assist in preparation of the section and to show the features of the coating more clearly.
For more information visit the American Galvanizers Association: American Galvanizers Association