DIP GALVANIZATION (H.D.G.)
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
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.
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
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.
basic guide to hot dip galvanizing (File
size: 176 Kb)
through galvanized coating showing pure metal zinc and zinc-iron
alloy layers which are the normal coating developments on rimmed
or aluminum killed steels.
through galvanized coating on silicon containing steel; Coating
is zinc-iron alloy which appears gray.
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.
more information visit the American Galvanizers Association: