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Uni-Coat™—Ductwork
Limitations
Fume Exhaust Systems
McGill AirFlow advises caution in specifying or using any polyvinyl chloride (PVC) plastic-coated, galvanized
steel ductwork (including its Uni-Coat products) for corrosive or condensing fume exhaust applications. The PVC
plastic-coated, galvanized steel is delivered in large coils with un-coated edges, and with coating imperfections
that may not be visible. The duct and fittings are made from the coils using conventional sheet metal ductwork
fabrication methods, including: burning, shearing, braking, rolling, rollforming and the use of screws and rivets.
The resulting products have many exposed edges and scratches, both inside and outside, in addition to the imperfections
in the coil coating. That means that bare steel and zinc would be exposed to what may be corrosive or condensing
fumes. McGill AirFlow’s Warranty does not cover the effects of corrosion.
Engineers must determine
the suitability of the Uni-Coat products and associated sealants based on the expected chemical or
condensation exposure of the ductwork interior. Installing contractors would be responsible for
coating or painting any exposed metal surfaces of the Uni-Coat ductwork, after the duct system has
been installed. McGill AirFlow and McGill AirSeal offer sealants and touch-up paint for Uni-Coat ductwork,
but their use does not assure a corrosion-resistant duct system.
McGill
AirFlow offers ductwork made from other materials that are more suitable for corrosive or
condensing fume exhaust duct systems, such as Types 304 and 316 stainless steel and Type 3003-H14
aluminum.
Temperature
The practical surface temperature range for using Uni-Coat ductwork is -30°F to +200°F. McGill AirFlow’s
Warranty does not cover the effects of extreme temperatures.
Exposed Duct Systems
McGill AirFlow does not recommend the use of PVC plastic-coated ductwork (including its Uni-Coat products) for
exposed applications in which appearance is important, unless the owner and engineer are willing to accept the
kinds of surface defects and appearance issues described under "Fume Exhaust Duct Systems" above
or do the necessary touch-up painting. Instead, McGill AirFlow recommends paintable galvanized steel ductwork,
to be prepared, primed, and painted after the duct system is installed.
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