oneclick 

Might have to dissolve an aluminium seatpost out of a steel frame - has anyone done this and how long did it take.

Russ Roth

Never tried it, or heard of it being tried, not certain how well it would work. But I've wondered if evaporust being constantly dribbled around the seam of the post/seat tube wouldn't break down the corrosive bonds.

Mad Honk 

It will take days and will likely ruin the paint on the frame unless you use a very dilute mixture and then it will take even longer, Good luck with the project. Smiles, MH

AdventureManCO 

NaOH...is that lye? If so, a few days, and cover your frame in grease + cling wrap + tape and you should be all set

ScottCommutes

I don't understand. If you are willing to damage the seatpost, wouldn't a giant pipe wrench get it to spin in like one minute?

PromptCritical 

Acid would be my last resort. The pipe wrench as mentioned above should do it. If not, cutting the seat mounting bracket off the top and using an easy-out should probably work (maybe in conjunction with the pipe wrench). Taking it to a machine shop and having them drill it out would work.

Two stroke motorcycles used to seize pistons incessantly. Here is a google search about how they deal with it.

https://www.google.com/search?q=how+...t=gws-wiz-serp

AdventureManCO 

Sometimes the posts are so stuck throwing them in a vise or using a pipe wrench can break the stays off. Usually the higher end the frame, the more delicate the operation required. I've also seen frames tied to trees with a come-a-long used to yank the seatpost out. Still, I'd imagine a lot of stress is put on the frame.

non-fixie 

I have dissolved a bar stem, using sodium hydroxide (drain cleaner). Took me (well, the sodium hydroxide - I just sipped my G&T's during the wait) no more than a couple of hours. I did keep the solution bubbling by adding more drain cleaner regularly. Have a look here.

Steel Charlie

It's all here
Time to rescue a stuck, jungle junker. The 1986 Jim Merz Allez!

AdventureManCO 

What is interesting is that in that thread, while there was some chatter about using lye, I elected not to and decided to try a couple other methods, more for the experience than anything else.

I used the hacksaw blade method for the seatpost, and a gigantic 30lb cheater bar for the stem. Both were stuck. I had a good 5ft+ of leverage on the stem, and it just *barely* came loose, and took and lot of back and forth. The post came out, but I don't think I'd use the hacksaw method again. I just don't have the touch lol. At least I didn't go through the frame! That experience made me appreciate lye even more, which I know is a very slim minority opinion on these forums, but oh well.

My final thoughts are:

low end-to-decent frame + nice seatpost: try the heat/clamp/pull/twist methods - but be careful w/ the twisting
low end-to-decent frame + crap seatpost: all the above, but add in the lye

high end frame + nice/rare seatpost: good luck!
high end frame + 'who cares' seatpost: lye only. If the frame is super thin tubing, or very delicate I'm using lye. It is completely harmless to steel, and there is no way I'm adding induced stresses to the frame by twisting and pulling. If you want to save the paint, try to plug the seat tube water bottle holes (if it has them), invert the frame, and let the lye spew out the bottom into a bucket when it starts to go. Still wrap the frame in armageddon-proof grease + cling wrap, etc. The only reason it ruined the paint on my Ironman when I removed a post on that one is because I didn't cover it. And it didn't bubble or strip the paint, it just discolored it.

clubman 

It took me two days with several top-ups of strong lye solution to remove about 4 inches of insertion. Yes I trashed some seat tube paint.

I think this would have worked well.

rancho66 

One day (8 hours) with my experience using this method, but paint was affected. Was going to Powdercoat frame so did not take precautions to save the paint. Gets hot and bubbly so take precautions of course. Poured water/acid solution into the bottom of the seat tube and let it eat the seat post from below.

Chombi1 

My brother tried the lye solution to melt away a stuck seatpost. He said it worked really quick and the seapost almost completely melted away overnight. He must have used a pretty strong lye solution. He said that it did not harm the bike's paint or the steel at all.

oneclick 

Note to all, as I see there are more than one -
NaOh is not an acid, it's a base.
Don't use acid - it'll attack steel.

dddd

Muriatic acid has long been used to dissolve smeared aluminum from iron cylinder walls after engine tuning failures.

Strong alkali solutions are known to embrittle steel, I've seen fractured cassette sprockets result from such soakings.

As was already mentioned, brute force methods can crack frame joinings.


I've used a lot of methods and have settled on use of a reciprocating saw with a suitably long/narrow blade. Always successful except with steel seatposts.

Don't cut in line with the clamping slot, and don't let the blade stroke exceed where the tip of the blade catches the opening of the tube!

Use a sharp blade and periodically probe the cut using a sharp, bent spoke to check for remaining aluminum which the sharp spoke will catch on.

The teeth will never even start to dig into the steel seat tube since there just isn't enough contact pressure to begin cutting alloy steel unless you're using a diamond blade.

Kabuki12

I have put the seat post clamped tightly in a big machine shop vise (mine) and turned the frame using the main frame , not the stays . This doesn’t always work due to the force it takes versus the possibility of tweaking the frame. At that point alternate measures are required. I don’t use lye to “dissolve” the alloy. I use ATF with just a bit of acetone and brush it on the seat post , wiping any excess from the paint . Then a gentle , rapid tapping on the post or stem. Let it sit for a day and repeat . The last stem and seat post that were stuck took a week and they both moved with only a little force on the frame. Both stem and seat post were salvaged.