Using Caustic soda (NaOH) to free stuck seatpost

Discussion in 'Cycling Equipment' started by Justin Brookman, Jun 13, 2003.

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  1. 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
     
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  2. Anonymous

    Anonymous Guest

    "Justin Brookman" <[email protected]> wrote in message
    news:[email protected]...
    > 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
     
  3. Simon Mason

    Simon Mason Guest

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

    > 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 http://www.simonmason.karoo.net
     
  4. Andy P

    Andy P Guest

    "Justin Brookman" <[email protected]> wrote

    > 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.
     
  5. > "Justin Brookman" <[email protected]> wrote in message
    > news:[email protected]...
    > > 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
     
  6. Andy P

    Andy P Guest

    > 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.
     
  7. Simon Mason

    Simon Mason Guest

    "Andy P" <[email protected]> wrote in message news:<[email protected]>...
    > "Justin Brookman" <[email protected]> wrote
    >
    > > 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
     
  8. Jim Edwards

    Jim Edwards Guest

    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 protected]> wrote in message
    news:[email protected]...
    > 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
     
  9. Tim Woodall

    Tim Woodall Guest

    On Fri, 13 Jun 2003 22:05:16 +0100, Andy P <[email protected]> wrote:

    >
    >> 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

    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.

    http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/
     
  10. The Mark

    The Mark Guest

    Andy P wrote:

    >
    >> 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.
     
  11. W K

    W K Guest

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

    > 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.
     
  12. The Mark

    The Mark Guest

    Jim Edwards wrote:
    > 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.
     
  13. Hywel & Ros

    Hywel & Ros Guest

    > 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
     
  14. On 13 Jun 2003 15:13:51 -0700, [email protected] (Simon Mason) wrote:

    > 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
     
  15. Simon Mason

    Simon Mason Guest

    "Jasper Janssen" <[email protected]> wrote in message
    news:[email protected]...
    > On 13 Jun 2003 15:13:51 -0700, [email protected] (Simon Mason) wrote:
    >
    > > 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
     
  16. Tbgibb

    Tbgibb Guest

    In article <[email protected]>, [email protected] (Justin
    Brookman) writes:

    >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.

    >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!

    >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.
    >
    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 protected]
     
  17. Andy P

    Andy P Guest

    "Tim Woodall" <[email protected]> wrote

    > 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.
     
  18. Andy P

    Andy P Guest

    "the Mark" <[email protected]> wrote

    > The warning about sulphuric and other strong acids is to do with the
    chance
    > 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.
     
  19. Tim Woodall

    Tim Woodall Guest

    On Mon, 16 Jun 2003 18:26:41 +0100, Andy P <[email protected]> wrote:
    > "Tim Woodall" <[email protected]> wrote
    >
    >> 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.

    http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/
     
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