This is an inspection on a short sale house. The house has some moisture issues, with mold on the walls and carpet. The HVAC duct has this white substance on it. I am not sure if it was manufactured this way or if it is the result of the moisture. It seems to be consistent on all the visible duct work, but, some of the elbows are smooth and shiny with a little bit of the white on it.
I’m not sure, but I think it’s galvanized.
That is what I am thinking, but the smooth shiny sections and the moisture issue has me wondering. I was not able to rub it off with my finger nail and it feels rough.
The smooth sections might be stainless…
The moisture wouldn’t likely cause mold to grow on metal. Mold grows on organics, and if there was any dust on the ducts for it to grow on, you could wipe it off.
Thanks Mark, you have been a great help.
Without a doubt Mike, that is in the galvanized plating. No worries mate!
Do a ph test on the white stuff and check the sheetrock.
That is oxidized zinc from the galvanized sheet metal. This happens if they leave the sheet metal stacked with moisture between sheets before it is formed into ducts. I have refused many shipments of sheet metal for this very reason. It is only a cosmetic problem as far as I can tell, but many customers balk when they see it.
Great explanation. I did not know that.
In the steel industry we called it white rust. As was said, it is an oxidation of the zinc coating.