I did some research and but I didn't find anything directly relevant. PVA is essentially glue. The msds for ICI pva indicates that on old work deglossing of shiny surfaces is recommended. I'd go with the finger nail test; if you can easily peel it off with a fingernail it should be removed. I suspect the galvanized hvac is sufficiently porous to allow for a relatively good bond by the pva. I would reprime with a metal primer and then paint.We are trying to paint new commercial ductwork but it has been sprayed w/ pva by the drywaller. Can we paint over this or does it need to be removed? Will the pva act as a primer or might we be in danger of the painted pva chipping off later?