Hummer

I have tried several methods to loosen things stuck on a bicycle frame. Some of the methods work some of the time.

Last year I watched a You-Tube video and saw the most successful method that I have seen.

Heat gun. Used for stripping paint and many other things. Available at hardware stores for about $50 US.

I have used the heat gun for seat posts, seized bolts, pedals stuck in cranks. I usually apply penetrating oil the day before. This has saved me lots of time and has less risk than some other methods.

I am surprised that no one else has seen this on You-tube.

dddd

Heat will work especially well where a longer length of the post is bonded in, due to the lengthwise expansion of the aluminum inside of a steel or even titanium seat tube, which breaks the bond to either side of the center of the bonded length.
Penetrant applied as the post cools is likely to be better drawn in, especially where the bond has broken between the tube and the post. I've used this method on a few quill stems, which twisted out with relative ease after everything cooled fully.

I don't know how much heat it would take to degrade the paint or decals on the seat tube, but a heated stem doesn't seem to get the headtube all that hot the way that heat will travel between a post and a seat tube.

dddd

Couldn't edit my above post to add the following:

Even without the differential thermal expansion, heat really softens the bonds of stuck metal parts like steel/steel cotter/cranks, allows cotter removal without bending the precious cotter.

unworthy1

the heat guns I own are H-O-T ! Even those with a "low" setting are significantly hotter than say a hairdryer on "high".
One thing they are made for is to remove paint, and they do, will scorch wood too so you have to develop the feel for where the limits are and be watchful.

zandoval 

After a good soak in PB-Blaster then use the freeze technique. Look it up on youtube. Freezing just might do the trick. You can use a brand name like Freeze Off ot just get a few cans of Air used for blowing out the grit on key boards. Just hold the can upside down to get the freezing liquid out (Usually Trifloro Ethane like).

cudak888 

It also eats thin steel. I had a steerer tube lose all of its threads and the steerer gain pits in the surface with that stuff.

-Kurt

dddd

I was considering that muriatic acid has long been the recommended chemical for removing smeared aluminum from engine cylinder walls, so unless it's left to sit too long (how long, I can't say), surely no one was recommending something that would readily pit the iron cylinder wall (which would cause loss of compression).

But you bring up a good point, since it might take a while to burn through a seatpost, and the operator might not know how long was long enough.

So I will have update my earlier comment to add that I recommend only mechanical removal, no chemicals (since they don't seem to be needed).

The caustic chemicals have bodily hazards as well, fumes, spatter, blindness and no doubt possibly death if used haphazardly.
At least they're not flammable!