Author Topic: Dissolving a stuck Seat post with Caustic Soda (FIXED)  (Read 40757 times)

Re: Dissolving a stuck Seat post with Caustic Soda (FIXED)
« Reply #100 on: 24 April, 2016, 07:49:33 am »
I'm trying this now... After 2 weeks of penetrating oil, then 2 weeks with the bike shop it's not moving. So there's now a 400g/l solution of NaOH in there and it's bubbling away nicely.

19 hours later and it's still bubbling!

Is it best to wait until it stops before pouring out and refreshing, or would a fresh solution be a good idea now? How long does the reaction go on for?
Quote from: tiermat
that's not science, it's semantics.

Re: Dissolving a stuck Seat post with Caustic Soda (FIXED)
« Reply #101 on: 01 May, 2016, 05:02:01 pm »
Still going...

Tried to get it out this morning, but it's not budging. It's hard to tell, but fishing inside with a bit of wire it looks like there's still a mm to go. The reaction is maybe a bit slow because of the ambient temperature - I warmed up the outside a bit and it really started going to the point where the exothermic-ness was self sustaining.

Patience, Grasshopper.
Quote from: tiermat
that's not science, it's semantics.

Re: Dissolving a stuck Seat post with Caustic Soda (FIXED)
« Reply #102 on: 02 May, 2016, 10:00:23 am »
It's OUT!


Preparation & PPE


Bubbling away nicely


Out in one piece


The last mm or so went pretty rapidly yesterday to foil-thickness, I think the heat was the key.
Quote from: tiermat
that's not science, it's semantics.

Re: Dissolving a stuck Seat post with Caustic Soda (FIXED)
« Reply #103 on: 02 May, 2016, 10:14:40 am »
I've washed out the frame, rinsed with 100 g/l citric acid solution and washed out again. The paintwork hasn't been damaged despite lots of frothing over. It was handy there was so much seatpost sticking out of the top of the frame.

Verdict: yes it works, but you have to be careful and patient. Overall cost: £5.00 for the caustic soda (not all used) and £5.95 for the safety glasses. I was quoted £120 to have it reamed out.
Quote from: tiermat
that's not science, it's semantics.