You might have some luck getting a corroded fastener unstuck by heating it, but you probably want to avoid soaking the fastener with penetrating oil or lubricant before applying a flame to it. With Freeze & Release, you can do the same thing with cold — get a fastener cold fast enough and the bolt and nut should contract at different rates, hopefully freeing the fastener — plus there’s no problem using penetrating oil to speed the job.
While most people have a torch of some sort lying around, there aren’t very many commonly available methods of freezing — that is, until now. Loctite recently released their Freeze & Release product that not only freezes the fastener to cause the needed differential contraction, but the spray also features a lubrication component to penetrate as the contraction cracks the corrosion.
A container of Freeze & Release can chill seized parts to -45ºF. Just shake the can and spray the seized fastener for 5-10 seconds, then wait 1-2 minutes for maximum effectiveness. If Freeze & Release doesn’t work after a few tries, you haven’t ruined the fastener and you can still try some other method.
There aren’t a ton of places carrying Loctite’s Freeze & Release yet. If you can find it, you could pay up to $10 a can.