2. Why Metal Coated Steel?
The basic purpose of coated steel is to prevent corrosion
and enhance the surface life of base metal. Zinc acts as a
cathodic protection and prevents the base metal from
corroding.
The coating protects the surface of the steel from oxidation
and it is also used to enhance the appearance of the
material.
Each of these coated steel has its own application,
depending on where they are used and to which
environment they would be exposed to.
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3. Metal Coated Steel Products
Galvanized (GI) – Hot Dipped & Electrogalvanized
Galvannealed(GA)
Galvalume (GL)
Galfan
Aluzinc
Pre-Painted Steel
Tin plate
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4. Metal Coated Steel Products
Only first 4 categories are considered in this
presentation, since they are the most widely used
coated steel products.
Aluzinc, Pre-painted Steel and Tin plate are not
covered in this article.
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5. Differences between coated Steel
Products
S.No
1
Parameter
Galvanized
Galvalume
Galfan
Zinc on Steel
Zinc reacts with
Iron to form Zn
Iron Alloy
43.5%-Zn;
55%- Al ;
1.5% Si
95% Zinc ;
5% - Al
Z
ZF
AZ
ZGF/ZA
Ducting,
roofing
Coating
Galvaneealed
Deep drawn
automobile parts/
outer panels
Metal
Buildings,
roofing
White
goods/some
auto parts
3
2
4
5
2
Coating Designation
3
Application
4
Corrosion Resistance
( 1 to 5 scale)
5
Spangle
Yes for HDGI
No
No
No
6
Process
Hot
Dipped/Electro
galvanized
Hot Dipped
Galvanizing
followed by
Annealing
Hot Dipped
continuous
Hot dipped
continous
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6. Trademarks
Galfan is the most recent invention of the above.
Galvalume and Galfan are registered and patented trademarks
brands and only those manufacturers with license from the
brand owners can produce and sell in these brands.
There are different grades within each variety of above products
based on
1.
Strength of the Steel.
2. Coating Mass – Amount of coating
3. Surface protection (Oiling, chemical passivation, organic
passivation)
4. Surface Quality
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7. Designation
Coated steel are normally designated as follows
Grade of steel + coating + spangle designation + surface quality + surface
treatment.
Just to give an example let us consider the grade,
DX53D ZF140 MBC
DX53D – Deep Drawing grade (European Standard).
ZF – Galvannealed
255 – Coating mass
M – Mini spangle
B – “B” type surface Quality
C – Chemical Passivation.
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8. Some Additional Info
American and European Standards are most commonly
used to designate the grades of coated products.
Color coated steel (Pre-painted steel) is normally on base
material of GI, GL. They are designated as PPGI and PPGL.
Products of GI and GL when sold without color coating or
pre-painting, they are referred as “Bare” GI or “Bare GL.
Pre-painted
Galvanised iron (PPGI) & Pre-painted
Galvalume (PPGL). PPGL is the famous of the two.
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