# Sodium Hydroxide vs. Stuck Aluminum Seatpost



## jtmartino (Jul 31, 2008)

Hey All,

I have an aluminum seatpost stuck in a lugged steel frame. I've tried nearly everything to remove it (short of the hacksaw down the seat tube trick) and all of my methods either bent tools, started to tweak the frame or completely destroyed the post. I've decided to pick up some NaOH (lye) to dissolve the aluminum.

My problem at the moment is sealing one end of the seat tube (either the BB end or the seatpost end) so the NaOH has a chance to soak without spilling out. The BB shell end is hard to seal up for obvious reasons - I don't want the solution getting into the down tube or the chainstays. For the life of me I can't seal the seat post end because the notch in the seat tube allows for water to leak out.

Currently I'm trying to use silicone sealant and a piece of bicycle tube (and a wine cork to hold it in place) inside the bb shell to seal that end off.

Anyone have any other recommendations? I've seen a couple videos online but they all seemed to have sealed seatposts or didn't go into details about the taping of the bike.


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## thomllama (Oct 3, 2007)

Spray foam insulation.. works great in the frame later on too what squeaks appear as it stops the dreaded sound travel/echo through the frame making it easier to find


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## eb1888 (Jan 27, 2012)

You've tried 50/50 acetone and ATF.


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## -Todd- (Jun 13, 2011)

stuff a rubber glove down into the post, fill the aluminum post with ice, and wrap the top part with a soft ice pack. get the post real cold. Then heat the frame with a hair dryer. before the ice melts, give it a smack with a mallett. 

Penetrating oil overnight will help, soft tapping will help it drive in further. 

Corrosion is a *****.


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## jtmartino (Jul 31, 2008)

thomllama said:


> Spray foam insulation.. works great in the frame later on too what squeaks appear as it stops the dreaded sound travel/echo through the frame making it easier to find


Oh man, that's a good idea. Will try it if I can't figure anything else out!



eb1888 said:


> You've tried 50/50 acetone and ATF.


I used half a can of PB blaster over the course of two weeks. And vinegar, and ammonia, and oxalic acid. None of that stuff worked!



-Todd- said:


> stuff a rubber glove down into the post, fill the aluminum post with ice, and wrap the top part with a soft ice pack. get the post real cold. Then heat the frame with a hair dryer. before the ice melts, give it a smack with a mallett.
> 
> Penetrating oil overnight will help, soft tapping will help it drive in further.
> 
> Corrosion is a *****.


I tried it - I even used a blow torch on the frame after soaking the seatpost in ice water (not too worried about the paint).

If I figure out a water-tight solution I'll take some pics and post them up here. Thanks for the suggestions!


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## tigris99 (Aug 26, 2012)

Simple can if pb blaster (auto part store) reapply 2-3 times over the course of and afternoon. The hair dryer in high or if ur skilled and careful a propane torch and warm up the seat tube. Twist seat post while pulling it out.


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## thomllama (Oct 3, 2007)

either get the next seat post painted/coated with a ceramic paint or can simply use never seize so it doesn't happen again.


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## customfab (Jun 8, 2008)

I've F'ed with a LOT of seized seat posts over the years. Seems all of the 'tricks' work some of the time but with mixed results. I'll never try any of them ever again though. Reaming a seized seat post out is the only way to go IMPO. It's not a quick fix but it's faster than screwing around with a half a dozen other things that fail only to resort to reaming it anyway. The basic set of harbor freight adjustable reamers are pretty appropriate for this task and will set you back ~$80, money well spent if you ask me.


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## Flamingtaco (Mar 12, 2012)

One more method, this one always works, is cheap, but requires elbow grease.

After cutting off the seatpost about an inch above the seatpost tube, use a mini hacksaw or electric ripsaw to cut a 2/3 section of the post along it's length. Make the two cuts are as parallel to each other as possible. Take your time so you don't cut into the tube. I typically cut harder at the exposed end of the seatpost and stop when the saw has cut through it and is about 1/8" from where the seat tube starts. I then zero out the angle and cut until I feel it is close.

Once both lines are cut, use vise grips to bend the 2/3 section inwards. If you have cut it enough, it will shear in the cuts easily. If it doesn't shear completely, bending it back and forth typically does the trick. I have sheared out aluminum like this with up to 1/8" remaining in the cuts, so this can be done without getting close to the frame. But the closer, the easier.

Once you have that piece out, use the vice grips to crush the top of the remaining 2/3 piece. This will allow you to pull it out 99% of the time. If not, open it back up and make one more cut in the center of this remaining piece. Crush with the vice again and it will bend at the cut and you can pull it out.


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## J.B. Weld (Aug 13, 2012)

It depends on the type of seat post but one method that I've had a lot of success with is to remove the seat, clamp the head of the seat post in a _very_ solidly mounted bench vice (frame upside-down) and then use the whole frame for leverage to twist and break the post free.


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## Slash5 (Nov 27, 2011)

I still like the one poster's idea to drill a hole sideways in the post, stick a bar of some sort in then run a air chisel/zip gun against the bar both directions to turn the post and to drive it up. Not much can stand up to the impact of an air chisel.
Almost wish I had a stuck post to try it on.


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## Mr. 68 Hundred (Feb 6, 2011)

I've never had to actually deal with this myself but I've seen the owner of the shop I used to work at do it several times. The various penetrating oils, heat/cool, air tools work most of the time. There was one though, that nothing touched it. He didn't try reaming it out like customfab said, but he should have.


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## reptilezs (Aug 20, 2007)

my never fail method for posts has been cutting a slot in it. i do the bulk removal with a sawzall


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## jtmartino (Jul 31, 2008)

tigris99 said:


> Simple can if pb blaster (auto part store) reapply 2-3 times over the course of and afternoon. The hair dryer in high or if ur skilled and careful a propane torch and warm up the seat tube. Twist seat post while pulling it out.


Unfortunately PB Blaster didn't work in this case. I tried it over the course of 4 or 5 days. Also tried the hair dryer AND blow torch method in conjunction with cooling the seatpost in ice.

Nada - there's probably 12 inches of seat post in the seat tube and it's frozen solid.



thomllama said:


> either get the next seat post painted/coated with a ceramic paint or can simply use never seize so it doesn't happen again.


Absolutely - I use anti-seize during post installs. This frame is a recovery/rehab effort.



customfab said:


> I've F'ed with a LOT of seized seat posts over the years. Seems all of the 'tricks' work some of the time but with mixed results. I'll never try any of them ever again though. Reaming a seized seat post out is the only way to go IMPO. It's not a quick fix but it's faster than screwing around with a half a dozen other things that fail only to resort to reaming it anyway. The basic set of harbor freight adjustable reamers are pretty appropriate for this task and will set you back ~$80, money well spent if you ask me.


Yeah, I may end up going this route if nothing else works. At least I'll have the tools for situations in the future.



Flamingtaco said:


> One more method, this one always works, is cheap, but requires elbow grease.
> 
> After cutting off the seatpost about an inch above the seatpost tube, use a mini hacksaw or electric ripsaw to cut a 2/3 section of the post along it's length. Make the two cuts are as parallel to each other as possible. Take your time so you don't cut into the tube. I typically cut harder at the exposed end of the seatpost and stop when the saw has cut through it and is about 1/8" from where the seat tube starts. I then zero out the angle and cut until I feel it is close.
> 
> ...


I heard this route works too. Will continue to try to dissolve the post (because I bought the sodium hydroxide already) but the next step is to start cutting.



J.B. Weld said:


> It depends on the type of seat post but one method that I've had a lot of success with is to remove the seat, clamp the head of the seat post in a _very_ solidly mounted bench vice (frame upside-down) and then use the whole frame for leverage to twist and break the post free.


I tried this, and totally destroyed the head of the seatpost. Then I tried clamping the post directly, and totally destroyed the post again.



Slash5 said:


> I still like the one poster's idea to drill a hole sideways in the post, stick a bar of some sort in then run a air chisel/zip gun against the bar both directions to turn the post and to drive it up. Not much can stand up to the impact of an air chisel.
> Almost wish I had a stuck post to try it on.


I tried to drill a hole and then torque on a steel bar I ran through it. Also used penetrating oil and a hammer. Totally sheared the post at the location of the hole. Maybe an air chisel would work, but unfortunately I don't have one. And I already cut off most of the crushed/torn up post


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## Psycle151 (Dec 20, 2005)

Some decent, mechanical ideas proposed here. But this is now the realm of chemistry, not mechanics. The OP mentioned trying ammonia earlier. In my experience, ammonia is THE go-to solution for aluminum/steel corrosion. But with that much post stuck in the frame, it's gonna take a while, if it works at all. 

My point is that ammonia is your only hope, and it's a long shot. Turn the frame upside down, fill up the seat tube with ammonia and don't hold your breath. Also, don't breath the ammonia.


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## jtmartino (Jul 31, 2008)

Psycle151 said:


> Some decent, mechanical ideas proposed here. But this is now the realm of chemistry, not mechanics. The OP mentioned trying ammonia earlier. In my experience, ammonia is THE go-to solution for aluminum/steel corrosion. But with that much post stuck in the frame, it's gonna take a while, if it works at all.
> 
> My point is that ammonia is your only hope, and it's a long shot. Turn the frame upside down, fill up the seat tube with ammonia and don't hold your breath. Also, don't breath the ammonia.


I checked the inside of the seatpost today - the NaOH is slowly eating away the post, but damn if it's not really, really slow. This is gonna take weeks!


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## customfab (Jun 8, 2008)

jtmartino said:


> I checked the inside of the seatpost today - the NaOH is slowly eating away the post, but damn if it's not really, really slow. This is gonna take weeks!


Aren't you in BendOR? if my memory is correct and you want to borrow my set of reamers you're welcome to them.


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## maelstrom331 (Feb 29, 2012)

If the paint is already shot ,take it to a place that does industrial sized radiators and ask to leave it in the stripping tank for a week.I stripped paint from some old steel frames this way and the guy asked if i got all the aluminum out cos there would be none left after.. not sure what they are using but something highly caustic


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## jtmartino (Jul 31, 2008)

customfab said:


> Aren't you in BendOR? if my memory is correct and you want to borrow my set of reamers you're welcome to them.


Good memory! I'm from Bend, currently living in the Bay Area. Thanks for the offer though!



maelstrom331 said:


> If the paint is already shot ,take it to a place that does industrial sized radiators and ask to leave it in the stripping tank for a week.I stripped paint from some old steel frames this way and the guy asked if i got all the aluminum out cos there would be none left after.. not sure what they are using but something highly caustic


Good idea, but the frame is not really valuable so by buying the $8 can of sodium hydroxide I'm nearing the limit of my budget. It's more of a fun project to see if I can do it!


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## brianbarber (Dec 23, 2010)

I read this thread when trying to extract an extremely stuck aluminum seatpost from a 1995 Kona Lava Dome frame. I had to resort to sawing it out. Here is my success story: The Experimental Runner: The Straight Goods on Removing a Stuck Seatpost. Thanks, everyone! Let the build begin...


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## Scott Novak (Mar 2, 2013)

I used ammonia sucessfully.

I had an aluminum seatpost stuck in a 1988 Schwinn High Sierra ChroMo frame. I laid plastic down on the floor. I didn't want any ammonia leaking down into the bottom bracket area, so I set the frame on it's side and propped it so the seat tube was parallel to the floor. Then about every hour I applied a bit of ammonia to the seat post.

The next day I used a block of wood on top of the seatpost and gave it a whack. It moved maybe a 1/32 of an inch. I had tried whacking the seatpost before the ammonia without any movement at all.

I applied more ammonia to the seatpost. I bolted on a seat and was able to barely turn the seat sideways. I continued to turn the seat back and forth and the seatpost began to slowly loosen up. Finally I was able to remove the seatpost.

I cleaned up the corrosion on the seatpost and cleaned the inside of the seat tube. I greased the inside of the tube and the seatpost and haven't had a problem since.

Scott Novak


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