1. www.knowyoursteel.com
by
Madhusoodhanan Sayeenathan
www.knowyoursteel.com

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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9. www.knowyoursteel.com