Originally Posted by
pothunter
I had a thought after I previously posted, and realise that I got tunnel vision about the seal and O ring becoming fused.
My original degree is Organic Chemistry and, having thought about it, my view is that an essentially inert amine type polymer, ie Nylon seal, or a Butyl compound, O ring, couldn't possible weld to a steel tube, (the butyl would dry out and become brittle).
To throw a variable in, it might be not the seal or the o ring, it could be the amounts of mineral oils and grease that have previously been applied which have dried out and formed a hard semi cross linked gum/polymer as the volatile elements have evaporated.
If you have more of these to do petrol, xylene, plus gas or any dino fuel type liquid might be more successful at bringing the hardened gum back into solution and make freeing easier.
Acetone and Isopropyl may have moved it in this case, but my thoughts are that is is more of a creeping liquid that has disrupted the mechanical bond, rather than any solvent effect.