Rust on ducts, and a couple other questions.

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Old 06-15-20, 01:11 PM
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Rust on ducts, and a couple other questions.

1. I inspected my ducts and found several areas where rust had made holes, so I removed all of them to inspect/clean/seal. I'm going to replace the sections with holes, but there were a few small areas where rust had started, but it's only on one side. Is there something I can put on those spots to stop it from rusting further, instead of replacing the section? This is the worst one... it seems to be from insulation sticking to the duct, in this case.




2. The insulation is old (30+ years), but it's still mostly intact. I plan on re-using most of it, unless there is a particular reason not to. Most is an unlabeled faced yellow fiberglass.




3. None of the ducts were sealed, so I'm going to seal all seams/joints with mastic (no tape, unless there is a reason to use it)... is there a preferred order of doing this? I would like to seal them and insulate outside of the crawl space, but I'm afraid the mastic might get disturbed during installation. If so, I'll just install and add mastic/insulation after.


 
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Old 06-15-20, 05:33 PM
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Probably not the insulation but moisture in the insulation.

Just get some Rustoleum rust red primer!
 
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Old 06-15-20, 05:44 PM
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Thanks Marq1, and yes you are right it was probably moisture in the insulation.

The worst places were the elbows below the registers... 3 or 4 had rusted all the way through the metal, and one had completely separated under the insulation. I guess condensation was settling in them over time... oh well, at least the elbows are cheap to replace... I'm just glad I decided to inspect them.


 
 

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