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topic 9946



I am a consulting engineer looking to specify material for a ductwork system that will be run exposed up the side of a building & painted with an epoxy paint.

My questions are:

1. Should the ductwork be galvanized? galvannealed?

2. Is there a special primer that needs to be used for either of the above?

3. What is the cost difference between galvanized & galvannealed sheet metal. (26 ga. w/ G90 coating)

Jason May
ENGINEERS - Princeton, New Jersey


Jason, have you considered fabricating the duckwork out of prepainted coil stock? This would avoid the need to prepare the ducts for painting in the field.

Roy Nuss
Trevose, Pennsylvania, USA

June , 2008

Hi, Jason. Galvanneal is very similar to galvanizing except it receives an annealing process to make it more appropriate as a paintable surface. So galvanneal would be better than galvanized. A primer designed for galvanneal is a good idea. I don't have cost figures but the additional cost of galvanneal must be small.


Ted Mooney, Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

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