Trying to dismantle a Marquipt Sea Stair boarding ladder that has been together for 33 years. The old 5/16" stainless machine bolts are threaded into aluminum and are cold welded, or seized, or whatever, they just do not move. Now that I have rung one off, I decided to ask if there are any suggestion on how to get the bolts out in one piece. Help would be appreciated.

Pete