keepitsimplespeed said:
wouldn't ammonia hurt the paint on the frame - and how do you get the ammonia into the seat tube?
The ammonia shouldn't hurt the paint, as long as you're not using the anhydrous stuff you use to cook meth with. Just dribble some down the post, like it was penetrating oil, and try to keep it away from lubricants.
Ideally, you could pull your BB, turn your frame upside down, and pour a bit more in, esp. if nothing happens via the other way.
Just because I hadn't seen it mentioned, but sometimes in desparate situations, tapping the seatpost IN a BIT can break the corrosion enough to get things started. Tapping on the post can also help the penetrant do its job.
Finally, never done this, but others had mentioned that the press-glued heads of posts often pop off long before one has had enough torque on them to free the post. Couldn't you drill holes through the shaft of the post, and fit a rod through, to give yourself some leverage?