Cured tank sealant properties

[Cholley6]

I'm in the process of building my tanks, I scuffed and cleaned the faying surfaces before dimpleing and cleaned again before installation. I have yet to install the baffle. Everything looks good so far...I think.

What does fully cured sealant feel like exactly? And how well does it adhere when not between surfaces? I've been checking the spots that had some sealant accidentally applied in the process of building. Granted, these areas were not prepped as they have no need for sealant, just accidentally applied spots. I can scrape the sealant off these areas if I try with a fingernail, not that easily though. I suppose I was expecting a chemical bond like epoxy has, just in a softer material. The sealant is no longer showing a fingerprint, and has a rubbery feel to it. I dont see how it could leak, fillets look to have been shaped well with squeeze out, shop heads all have a nice Hershey kiss covering, but I am concerned due to lack of experience.

 

[daveyator]

Sounds like you’ve got it right. Once cured the sealant feels rubbery and is not at all sticky to touch. I’ve always just used a fingernail to remove any odd bits splattered around. It takes a few days to go off properly. I vaguely recall seeing 96 hours on a data sheet somewhere. Colder weather means slower cure. I usually put a couple of lumps on a bit of scrap aluminium as a control piece. So I’m not tempted to poke my nice tidy pro seal work.

 

[fixnflyguy]

It never really "hardens", but rather cures to a density that seals and doesn't flow, but expands/contracts with temperature and structural flex. I have a ton of experience with Proseal and the derivatives in the large aircraft world as well as RV's. Fully cured "old" sealant removal is still accomplished with sharpened plastic scrappers that will leave nothing but the bondline residue. My go -to final clean is red scotchbrite, clean with acetone or MEK and final clean with Coleman camp fuel just before application. In large jets, Boeing/Airbus we just use the MEK or Acetone, sometimes Alcohol..main thing is dry wipe it rather than allow evaporation with cheescloth or clean cotton wipes. As others mentioned, I always make a "test card" blob with sealant batch # and date to hang on the wall for cure confirmation.

 

[Cholley6]

Thanks for the info. It certainly feels like I would expect it to feel. Almost like a molded in place gasket.