Chemical seatpost removal

Tootyred

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So as some of you will know, i took a chance on an 88 Bear Valley with a stuck post. Mainly as it was reasonably cheap and more importantly my humungous 20.5" c to c size .

The previous owner was very honest and pointed out several times it was stuck......but then there's stuck and STUCK!

This one proved to be the latter......so.....

5 days of supercrack and penetrating oil....fail.
Concussive shock (not too much just air impact with an old socket on top).....fail.
Pipe freeze spray with lagging x3 goes till old tube ran out.....fail.

So its time for some alchemy. Which got it out. Thought i might share the method with you and what i learnt.

Firstly the post was already toast as the previous owner had had several goes in a vice, grips, hammer etc. Pitty as it was an xc pro post! But hey ho. If you want to keep the post try something else as you will have NOTHING left at the end.

Secondly, this method ONLY works on ALLUMINIUM posts in STEEL frames.....i cant stress that enough. The chemicals can't dissolve steel, but can dissolve alluminium......THEY CANT TELL A FRAME FROM A POST, DONT USE THIS ON AN ALLUMINIUM FRAME!

Thirdly, safety first! This is dangerous stuff, it burns.....badly......and will blind you. It also gives of hydrogen as a byproduct. So out doors, no naked flames etc.

If you have any doubts....don't do it.

Still going to try.....excellent.....So you will need for this.

1kg of sodium hydroxide crystals (caustic soda....but check the percentage you need it pure)
Water
Pair of marigolds
Mixing jug......no....not the one from the kitchen!
Safety glasses or better goggles
Mask....able to cope with gas.....depending on location of experiment.
Mixing stick
Tape, bluetack, plumbers mate, potato, prosecco cork for bunging up holes.
 

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Tootyred

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So, to start you need to bung up the holes in the frame and stop the fluid getting out of the seatpost. I used plumbers mate for the smaller holes in the bottom bracket and a champagne cork in the seatpost.

I also put a blob of plumbers mate on the other side of the bb as this make pouring the liquid in easier.

Find somewhere to stand the frame.....no not the new patio or the kitchen carpet as all kinds of nasty black goo is going to come out.

Now mix your brew. I found 200ml of water with 100g of sodium hydroxide poured was about right.....don't thin it out or the reaction seems not to work....don't put more in as it won't dissolve. POUR THE POWDER SLOWLY INTO THE WATER AND STIR.....DO NOT TIP WATER ON THE CRYSTALS. This could be bad.

This is an thermic reaction and the container will get hot.

Carefully pour in the liquid till in my case it ran out the bottle cage hole.......stand back....wait.
 

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gtturbo

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Following this as I've got a 92 GT Bravado where a previous owner has some how managed to remove the seat post but leave some still stuck a few inches down the seat tube so this is my only option. Interesting my 88 BV also had a stuck XC Pro post, maybe they were fitted OE for some reason ?. Lucky for me the freeze trick worked so I salvaged it.
 

Tootyred

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Next is the fun bit. The liquid will start to boil in the tube. Water and gas will pour out the bottle cage hole and hydrogen gas will escape from the top. This shows the reaction is working. It should sound like a coffee machine.

You can see the gas coming out in the photo.....ive got a video.....when i can work out how to upload it!
 

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Tootyred

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Once it all goes quiet and you can hear no more bubbling tip out the slop that's left.

Then repeat with a refill.

After i realised it was definitely working, i cut off a section of the post to check progress.

You can see the difference between where the cork kept the chemical at bay and the contact area. This was after 3 fills. Each takes approx 30 mins from fill to the reaction stopping. I just did gardening in between so i could be outside to keep and eye on it!
 

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Tootyred

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It took 10 loads to completely dissolve the post. Nothing left.

The last bit ( protected by cork) i pulled out you can see how thin it got.
 

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Tootyred

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Lastly, gave the frame a good "tin foiling" (see hints and tips page for my previous utterance on this).

Bobs your auntie, fannys a rude word......job done.

Before and after tin foiling below.
 

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Tootyred

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Finally, a word on paint......it didn't seem to effect my paint, but then its already knackered and its going off to powder anyway. In theory!!......THEORY.....it sould not eat your paint. I did notice id dulled the clear coat, but this polished out with t cut.

I was also careful to wipe you spills/ spray the frame with a hose every so often to stop it accumulating. This could easily strip paint i should think in prolonged contact.

Secondly, i hear it WILL strip metallics.....because the glitter is often alluminium. Qed.

Hope this helps somebody out.

All the best......but.....please be careful, this is not some safe, diy, hse certified home use chemical.....it will hurt you badly if you don't respect it.
 

BlackCat

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Burns badly? Risk of blinding? Destroys everything on contact?

Perfect. Let’s get started.

(In all seriousness, though - good tip thread)
 
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