Using Caustic soda (NaOH) to free stuck seatpost

"Justin Brookman" <[email hidden]> wrote in message
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Quoted message said:

Hi all

I've read with interest the posts concerning freeing a stuck aluminmium seatpost with caustic
soda, and have had a go at it yesterday. It was a bit hairy and their was no doubt that a chemical
reaction did occur. (bubbling and foaming) However I'm wondering how long to leave it marinating
before hvaing a go at getting it out. Also I'm unsure what strength solution is needed, the
caustic soda came in granules to be mixed with water, I mixed it a five times drain cleaning
strength, approx 250 ml(or 250 grams I can't remember) of granules to 400 ml of water.

Does anybody no what strength is needed and more importantly what strength is too dangerous?

Dunno about what's needed, but 250 g granules in 400ml water is jolly strong. I'd be _very_ careful
with the resulting fluid. It's possibly strong enough to heed the warnings about diluting strong
things - add the fluid to a large body of water, don't add water to the fluid, it will get hot and
possibly worse. Probably wear eye protection, and don't get it on your skin.

cheers, clive

"Justin Brookman" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Does anybody no what strength is needed and more importantly what strength is too dangerous?

For heavens sake don't get it in your eyes, or on your skin. It's very nasty stuff conc. Sodium
Hydroxide. It also gives off hydrogen on contact with the Al which is the bubbling you saw.

I can't see how it will free a seat post and leave it undamaged. The caustic will attack the Al and
leave it pitted - you would have to spend a while polishing it up afterwards.
--
Simon Mason Anlaby East Yorkshire. 53°44'N 0°26'W simonmason.karoo.netsimonmason.karoo.netOpen ↗

As ever, Sheldon The Wise has some Clue to dispense on this:
sheldonbrown.comstuck seatposts.htmlOpen ↗

Dave Larrington - legslarry.beerdrinkers.co.uklegslarry.beerdrinkers.co.ukOpen ↗
===========================================================
Editor - British Human Power Club Newsletter
bhpc.org.ukbhpc.org.ukOpen ↗
===========================================================

"Justin Brookman" <[email hidden]> wrote

Quoted message said:

I've read with interest the posts concerning freeing a stuck aluminmium seatpost with caustic
soda, and have had a go at it yesterday. It was a bit hairy and their was no doubt that a chemical
reaction did occur. (bubbling and foaming) However I'm wondering how long to leave it marinating
before hvaing a go at getting it out. Also I'm unsure what strength solution is needed, the
caustic soda came in granules to be mixed with water, I mixed it a five times drain cleaning
strength, approx 250 ml(or 250 grams I can't remember) of granules to 400 ml of water.

Does anybody no what strength is needed and more importantly what strength is too dangerous?

Caustic soda is classed as corrosive (ie will burn your skin and more importantly your eyes) at 20
g/l. If what you've got is pure industrial or laboratory type stuff then the strength you say you've
mixed is about 30 times this. Not sure how long you could leave it on your skin before some serious
burning ocurred but I've been burnt by solutions much weaker than that because I didn't get to a tap
quick enough and I certainly woudn't want it in my eyes at all. Keep a bucket of water close by.

Quoted message said:

"Justin Brookman" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Hi all

I've read with interest the posts concerning freeing a stuck aluminmium seatpost with caustic
soda, and have had a go at it yesterday. It was a bit hairy and their was no doubt that a
chemical reaction did occur. (bubbling and foaming) However I'm wondering how long to leave it
marinating before hvaing a go at getting it out. Also I'm unsure what strength solution is
needed, the caustic soda came in granules to be mixed with water, I mixed it a five times drain
cleaning strength, approx 250 ml(or 250 grams I can't remember) of granules to 400 ml of water.

Does anybody no what strength is needed and more importantly what strength is too dangerous?

Dunno about what's needed, but 250 g granules in 400ml water is jolly strong. I'd be _very_
careful with the resulting fluid. It's possibly strong enough to heed the warnings about diluting
strong things - add the fluid to a large body of water, don't add water to the fluid, it will get
hot and possibly worse. Probably wear eye protection, and don't get it on your skin.

cheers, clive

Thanks Clive, yes I definatley wore safety glasses. Does anyone else no if 5 times recommended drain
cleaning strength (250g of NAOH granules in 400ml of water) is strong enough or how long to leave it
before trying to shift it?

Justin

Quoted message said:

Dunno about what's needed, but 250 g granules in 400ml water is jolly strong. I'd be _very_
careful with the resulting fluid. It's possibly

strong

Quoted message said:

enough to heed the warnings about diluting strong things - add the fluid

to

Quoted message said:

a large body of water, don't add water to the fluid, it will get hot and possibly worse.

That warning's just for diluting concentrated sulphuric acid as far as I know. Always safer to add
the acid to water (or you can add a proportionately large volume of water very quickly without too
much danger if for example you've spilled some). I don't think it's a general problem. I'd have
thought dissolving 250g of NaOH in 400ml of water would have been enough to get extremely hot and
give off corrosive fumes whichever way you add the two. I can remember an experience with a very
wobbly 200l drum and a sore face in a previous life as an electroplater. Perhaps I'll make some up
on Monday & pop a bit of Aluminium in to see how fast it reacts.

"Andy P" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"Justin Brookman" <[email hidden]> wrote

Quoted message said:

I've read with interest the posts concerning freeing a stuck aluminmium seatpost with caustic
soda, and have had a go at it yesterday. It was a bit hairy and their was no doubt that a
chemical reaction did occur. (bubbling and foaming) However I'm wondering how long to leave it
marinating before hvaing a go at getting it out. Also I'm unsure what strength solution is
needed, the caustic soda came in granules to be mixed with water, I mixed it a five times drain
cleaning strength, approx 250 ml(or 250 grams I can't remember) of granules to 400 ml of water.

Does anybody no what strength is needed and more importantly what strength is too dangerous?

Caustic soda is classed as corrosive (ie will burn your skin and more importantly your eyes) at 20
g/l. If what you've got is pure industrial or laboratory type stuff then the strength you say
you've mixed is about 30 times this. Not sure how long you could leave it on your skin before some
serious burning ocurred but I've been burnt by solutions much weaker than that because I didn't
get to a tap quick enough and I certainly woudn't want it in my eyes at all. Keep a bucket of
water close by.

I got one drop of 1.5 M Potassium Hydroxide in my eye and it blinded me for a fortnight. It made
the cornea opaque.

Simon

I have never heard of using NaOH to free a seat post, but you may want to flood the area with cheap
vinegar when you are done to neutralize the caustic. Then multiple flushings of H2O to get it off
the bike. You could even use beer to neutralize the NaOH or the vinegar.Beer has a lot of buffers.
Sounds like a pretty good idea for a party. Jim

"Justin Brookman" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Hi all

I've read with interest the posts concerning freeing a stuck aluminmium seatpost with caustic
soda, and have had a go at it yesterday. It was a bit hairy and their was no doubt that a chemical
reaction did occur. (bubbling and foaming) However I'm wondering how long to leave it marinating
before hvaing a go at getting it out. Also I'm unsure what strength solution is needed, the
caustic soda came in granules to be mixed with water, I mixed it a five times drain cleaning
strength, approx 250 ml(or 250 grams I can't remember) of granules to 400 ml of water.

Does anybody no what strength is needed and more importantly what strength is too dangerous?

Thanks for any input

Justin

Andy P said:

Quoted message said:

Dunno about what's needed, but 250 g granules in 400ml water is jolly strong. I'd be _very_
careful with the resulting fluid. It's possibly

strong

Quoted message said:

enough to heed the warnings about diluting strong things - add the fluid

to

Quoted message said:

a large body of water, don't add water to the fluid, it will get hot and possibly worse.

That warning's just for diluting concentrated sulphuric acid as far as I know. Always safer to add
the acid to water (or you can add a

It's a good idea for diluting anything. If it's going to fizz/boil/bubble/ splash whatever, you
would rather it was the diluted stuff than the conc stuff.

Regards,

Tim.

--
God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t," and there was light.

tjw.hn.orgtjw.hn.orgOpen ↗ locofungus.btinternet.co.uklocofungus.btinternet.co.ukOpen ↗

Andy P said:

Quoted message said:

Dunno about what's needed, but 250 g granules in 400ml water is jolly strong. I'd be _very_
careful with the resulting fluid. It's possibly strong enough to heed the warnings about diluting
strong things - add the fluid to a large body of water, don't add water to the fluid, it will get
hot and possibly worse.

That warning's just for diluting concentrated sulphuric acid as far as I know. Always safer to add
the acid to water (or you can add a proportionately large volume of water very quickly without too
much danger if for example you've spilled some). I don't think it's a general problem. I'd have
thought dissolving 250g of NaOH in 400ml of water would have been enough to get extremely hot and
give off corrosive fumes whichever way you add the two. I can remember an experience with a very
wobbly 200l drum and a sore face in a previous life as an electroplater. Perhaps I'll make some up
on Monday & pop a bit of Aluminium in to see how fast it reacts.

Adding water to sodium hydroxide will get hot, a small amount of water added to a lot of sodium
hydroxide can be too hot to touch.

The warning about sulphuric and other strong acids is to do with the chance of it *spitting*, the
reaction is a lot more violent.

If you get any on your skin though always wash off with *copious amounts of water*, to use the
safety phrasing.

A lecturer when I was at college 20 odd years ago used to tell of an incident when he was working in
Africa about someone who spilled a lot of sodium hydroxide on his legs and his workmates wanted to
neutralise it with sulphuric acid.
--
Mark

I've got a something special being built for me.

"Tim Woodall" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

It's a good idea for diluting anything. If it's going to fizz/boil/bubble/ splash whatever, you
would rather it was the diluted stuff than the conc stuff.

Its generally not a problem unless its conc sulphuric.

NaOH pellets into water does create some heat, but not that much. Strong NaOH solution -> weak [*]
won't give out much heat at all (if any)

[*] OK I mean less concentrated not weak.

Jim Edwards said:

I have never heard of using NaOH to free a seat post, but you may want to flood the area with
cheap vinegar when you are done to neutralize the caustic. Then multiple flushings of H2O to get
it off the bike. You could even use beer to neutralize the NaOH or the vinegar.Beer has a lot of
buffers. Sounds like a pretty good idea for a party. Jim

When everyone is so drunk an throwing up the stomach acid should help to neutralise it too. :-)
--
Mark

I've got something special being built for me.

Quoted message said:

acid to water etc. Its generally not a problem unless its conc sulphuric.

NaOH pellets into water does create some heat, but not that much. Strong NaOH solution -> weak [*]
won't give out much heat at all (if any)

Not so ! If you add NaOH pellets to water it generates a lot of heat; easily enough to boil the
water. I've done it !

Strong solution + more water will be OK (probably)

I guess you know this already, but alkali is extremely bad for alluminium, and I'd be very loth to
trust my weight to a seat post so treated. Or are you trying to dissolve it away and aren't bothered
? I'd start with applying WD40 daily for a week - or have you given up on this already ?

Cheers

Hywel

(Simon Mason) said:

I got one drop of 1.5 M Potassium Hydroxide in my eye and it blinded me for a fortnight. It made
the cornea opaque.

Wow. You had an incredibly narrow escape there if it cleared up again.

Jasper

"Jasper Janssen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

(Simon Mason) said:

I got one drop of 1.5 M Potassium Hydroxide in my eye and it blinded me for a fortnight. It made
the cornea opaque.

Wow. You had an incredibly narrow escape there if it cleared up again.

Jasper

They said it was 'cos I was about 19 at the time and was young enough to recover.

Simon

In article <[email hidden]>, [email hidden] (Justin

Brookman) said:

I've read with interest the posts concerning freeing a stuck aluminmium seatpost with caustic soda,
and have had a go at it yesterday. It was a bit hairy and their was no doubt that a chemical
reaction did occur. (bubbling and foaming)

Ya, you get hydrogen (among other things) out of this. It is the same reaction you get with the
product called "Drano" which is NaOH with Al shavings in it.

Quoted message said:

However I'm wondering how long to leave it marinating before hvaing a go at getting it out.

I have never tried this, but extreme caution is called for. What kind of tubing do you have on the
bicycle? Please tell us it isn't Al!

Quoted message said:

Also I'm unsure what strength solution is needed, the caustic soda came in granules to be mixed
with water, I mixed it a five times drain cleaning strength, approx 250 ml(or 250 grams I can't
remember) of granules to 400 ml of water.

Does anybody no what strength is needed and more importantly what strength is too dangerous?

That, as others have indicated is a potent strength. I was glad to hear of you using saftey glasses.
Personally I'd start with a weaker solution, but I say that not out of experience with extracting
seat posts, but out of experience with NaOH.

Quoted message said:

I'd be concerned with the effect on the steel tubing of the bike it self. I'd probably make a weaker
solution and give it about 15 minutes in the tube and then wash it out and neutralize it. Then I'd
go after the tube with WD-40 and muscle power and see if it would budge. And I would start something
like this only after trying all the remedies offered on Sheldon Brown's web site.

Tom Gibb <[email hidden]

"Tim Woodall" <[email hidden]> wrote

Quoted message said:

It's a good idea for diluting anything. If it's going to fizz/boil/bubble/ splash whatever, you
would rather it was the diluted stuff than the conc stuff.

A better idea would be to gain some knowledge of whatever chemicals you are using first and exercise
the appropriate care.

"the Mark" <[email hidden]> wrote

Quoted message said:

The warning about sulphuric and other strong acids is to do with the

chance

Quoted message said:

of it *spitting*, the reaction is a lot more violent.

At the risk of sounding pedantic (but hey it makes achange from chain lubricants and helmets!)
there's nothing inherently dangerous about adding water to hydrochloric or nitric acid. It's just
sulphuric that's a bit iffy.

Andy P said:

"Tim Woodall" <[email hidden]> wrote

Quoted message said:

It's a good idea for diluting anything. If it's going to fizz/boil/bubble/ splash whatever, you
would rather it was the diluted stuff than the conc stuff.

A better idea would be to gain some knowledge of whatever chemicals you are using first and
exercise the appropriate care.

There aren't many chemicals that can't splash when being diluted. But adding the acid/alkali to the
water is standard practice. (Obviously when bringing a solution up to volume you need to top off
with water at the end)

<http://www.kent.ac.uk/physical-sciences/safety/chemicals.htm>

Corrosive Chemicals The common ACIDS and ALKALIS (e.g. sulphuric acid, hydrochloric acid, nitric
acid, sodium hydroxide, potassium hydroxide) cause most chemical burns so great care should always
be taken when using them. When diluting, always add acid to water and not vice versa. If you are
splashed with acid or alkali, wash immediately with large quantities of cold water.

Tim.

--
God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t," and there was light.

tjw.hn.orgtjw.hn.orgOpen ↗ locofungus.btinternet.co.uklocofungus.btinternet.co.ukOpen ↗