I like the double nut and/or puller idea. Pullers are awesome things (you can get a decent one for about 20$ that should work). Don't forget the power of vibration (ie bang on it like a cowbell...ever see your mom tap around a jar lid lightly and repeatedly to loosen/get it open? It works I tell ya). Penetrating oil/PB Blaster works too but needs a way in there to work between frozen parts....hence tapping helps here too. Double nuts with no thread showing has added bonus of allowing you to tap/bang on the nut w/o destroying threads.
Acid is evil stuff in general and will make things worse if you don't know what you're doing. Don't do it.
Summary: PBBlaster/vibration/puller.
Don't forget to add love, beer, and plenty of cursing....let us know
nobody said it was easy
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