galvalume panels provide an acceptable appearance.
If factory color finish is not required, document
the rationale for the decision in the design
analysis and delete this paragraphs and related
subparagraphs.
The US metal building industry offers a variety of
color finishes to protect the metal panels against
chemical corrosion and ultraviolet radiation; to
provide long life with minimum maintenance plus
acceptable weathering and color retention; and to
assure chalk, fade, and mar resistance. Some of the
most widely used coatings include, but are not
limited to, the following:
a. Polyvinylidene fluoride (PVDF2); a nominal 0.025
mm (1 mil) thick coating modified with a proprietary
resin for toughness; it may be used in most
environments.
b. Silicone-modified polyester (SMP); a thermoset
coating system composed of polyester resin modified
by copolymerization with a functional silicone resin
intermediate designed for added protection against
chemical corrosion and ultraviolet radiation.
c. Plastisol (PVC); a two-coat system consisting of
a polyvinyl-chloride resin dispersed in a
plasticizer top-coat over a corrosion-resistant
primer; it is a high-performance, thick coating
designed for highly aggressive and corrosive
environments with excellent resistance to common
acids, alkalis, and inorganic compounds.
Most coatings may be ordered extra-thick for
buildings in direct contact with salt or chemical
laden air or where a premium finish would be
justified. The thicker coating provides additional
primer and increases the coating's corrosion and
abrasion resistance, but it requires a special run
by the coil coater and additional delivery time.
Appropriate specification requirements must be added
if thick film coatings are to be used. Clear coats
may also be added to the finish color coated coil to
enhance the coatings performance.
The baseline values included in this specification
are for a standard 0.025 mm (1 mil) PVDF2 (i.e.,
Kynar 500, Hylar 5000) coating system. If a
different coating type or thickness is required,
research the coating type and modify indicated
values accordingly. Coordinate with the coating
type specified elsewhere in this section.
Corrosion of galvanized steel panels, together with
the fact that cut edges, scratches and penetrations
of the panels expose the steel substrate, warrants
consideration for the use of aluminum panels in salt
spray and other corrosive environments; however, the
SECTION 07412
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