I'm in the process of resolving a moisture problem in our walls. I posted about this earlier here: Wall Rot: Water, Mold and Ants
The source of the moisture is a dryer ventilation duct that runs through
a concrete floor. Vapor is leaking out through a joint in the duct. Then it moves up between the duct and the concrete into
an adjacent wall. It caused a bit of a mold problem that can be seen in the thread linked above.
At some point, I'm going to re-route the vent so that it doesn't go through the concrete, as I believe the concrete route is problematic, and it will allow us the use of a corner in the room that is currently occupied by the duct. Due to the location of the dryer, running new duct is quite a project (there is concrete in the way and it's very difficult to get duct to a crawlspace or exterior wall).
In the meantime, I'm looking for a solution to seal a joint in the duct. The joint I need to seal is pointed out on one of the attached images. The arrows point right to it.
If I had access to the exterior of the duct, I'd use foil tape. The exterior of the duct isn't accessible, however, as it's embedded in concrete. If I clean the metal well, will a caulk properly seal this joint from the inside? If so, what kind of caulk? Silicone? Latex? Is there another approach I should take to sealing this joint?