The
Facts
Galvannealed
steel (standard galvanized) is coated with a Zinc-Iron Alloy by a process
known in the metallurgical technology, as the Hot-Dip Process. This
process consists of passing cold reduced sheet steel in coil form
continuously through a pot of molten zinc. As the steel leaves the pot,
the amount of coating allowed to remain on the sheet is controlled by
coating rolls, which are used to establish minimum coating weights in
accordance to ASTM
Designation A525/A525M.
The zinc coating is what protects the steel against corrosion. This
protection acts in two ways. The zinc acts as a shield between the base
steel and the atmosphere and when the base steel is exposed, such as at
sheared or blanked edges, the zinc acts as a galvanic protector,
sacrificing itself in the presence of corrosive elements. The coating
structure consists of a layer of zinc superimposed on a thin alloy layer
consisting of both iron and zinc. The solidification of the zinc layer
results from crystallization of the bath metal.
Galvannealed
products are increasingly in demand. They are found in a wide variety of
applications requiring long-term maintenance-free corrosion protection,
such as, bridges, pulp and paper mills, recreation centers, utility
industries, oil refineries and petrochemical industries, automotive
industry, and for miscellaneous highway uses, such as guard rails, lights,
signs and fencing. Why in so many applications? Because standard
galvanized products offer the most economical corrosion
protection for steel.
Why
you should specify Galvannealed Steel over Cold-Rolled Steel (CRS):
-
Purchasing
cost of sheet metal is competitive.
-
Reduced
preparation and painting costs.
-
Provides
considerably longer life-expectancy.
-
Delivers
excellent resistance to corrosive elements.
-
Offers
superb paint adhesion characteristics.
-
Requires
minimal maintenance.
Galvanneal
Steel is designed to combine strength, paintability and resistance to
corrosion by using zinc coating as a rust inhibitor.
The main property of zinc is its very slow oxidation rate which
causes it to act as a long-lasting protective barrier against atmospheric
corrosion as long as it remains on the steel core.
During manufacturing, the galvanizing process is completed when the
excess zinc has been removed from the core leaving a zinc-alloy surface,
spangle-free, gray in color, and after proper cleaning it's well suited
for finish painting (and eliminates the need for prime painting).
MDI®
standard
doors, frames and components are fabricated with commercial quality A40
Galvannealed (Satincoat) Steel with a minimum zinc coating of .40oz/sq ft.
Heavier coating of 1.25oz/sq ft, known as G90
Galvanized steel is also available for extreme atmospheric conditions.
By
offering superior resistance to corrosion and eliminating the need for
prime painting, Galvanneal Steel reduces costs associated with special
preparations, handling and maintenance of inferior materials such as Cold
Rolled Steel, thus allowing us to offer a better product at a competitive
price. Even when primed and
finish painted, Cold Rolled Steel is more susceptible to rust and
corrosion from the inside-out, because a door is not prime-painted on the
inside, leaving the bare CRS exposed to moisture.
Galvanneal
Steel doors and frames are now specified world-wide for an ever expanding
range of architectural projects. Government,
military, educational, institutional and commercial entities in the United
States, are increasingly demanding the higher quality offered by
Galvanneal Steel.
For
more information on the the application of various types of steel
please contact our customer service department at: 516.294.1801 or
e-mail us at: info@metropolitandoor.com.
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