Citric Acid and steel...

Discussion in 'Fettling Forum' started by John Leah, Nov 19, 2009.

  1. John Leah

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    I've just tried cleaning some brass parts in a solution of citric acid and was surprised at just how quick and effective it is.

    However, is there any reason I shouldn't immerse ferrous metal parts? For example, my Valor has steel pan supports brazed to the brass tank. Trawling the fettling archive proved inconclusive as there seemed to be advice to protect jet needles while another used a citric acid based product to de-rust a tank.

    I suppose I'm concerned the acid may etch the steel leaving it pitted - but, on the other hand, I do have some rusty steel parts I'd like to clean up.

    Cheers,
    John
     
  2. Bom Bom Bom Bom

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    Hi John,

    The key thing is not to immerse two different metals at the same time otherwise you set up a galvanic circuit with the less noble metal plating the more noble (I think I've got this the right way round).

    Citiric acid would work for ferrous metal on it's own but for other than a very light covering I wouldn't use it as it would work by dissolving the rust whilst at the same time dissolving some of the sound metal. This is the same when cleaning brass which is why you shouldn't leave the brass in the acid too long or use too strong a solution.

    For rust I would tend to use a proprietary solution to ever remove the rust, or to chemically convert the rust whilst leaving the existing sound metal alone. Or if it's a large piece (like a 111 case for example) you could use electrolysis - but again you couldn't mix metals with this approach.

    Cheers, Graham.
     
  3. John Leah

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    Thanks Graham,that makes perfect sense.

    Cheers,
    John
     
  4. Lance

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    John i have done both, mixed metals, and done them alone. What happens to the iron/steel is it turns black just as it would if you were using an electrolsys system. However the action time is much slower if you do them together. The brass will clean up fairly quickly and the steel takes on a dark nearly black appearance. This is not something to lose sleep over as it wipes right off but still it is a bit disconserting when you first see it.

    In my experience, as for setting up a galvanic reaction, unless you introduce a current it's not going to happen. You have to USE the electricty you are making before the metals will react. At least to my knowledge you do. By that i mean if you attach a wire to the brass and another to the steel and then either apply a current or attach them to make "work" the electrical potental is just going be just that potental. Granted if you left them in solutation for 4 weeks or maybe months, i expect you would see some action.

    Now that has been my experience your milage may differ.

    lance
     
  5. Bom Bom Bom Bom

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    Hi Lance,

    I think the fact you are seeing the brass clean up really quickly and the steel "turns black just as if you were using an electrolysis system" is actually proof that you are seeing a reaction and a galvanic circuit created.

    Cheers, Graham.
     
  6. Lance

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    4b i would agree if the circut were being used.

    We know that if you attach leads to a voltmeter and put the two leads into a lemon you will see the presents of a circut. The voltometer will register the current flow. But it is a completed circut, a positive and a negitive pole connected through the meter, reacting to the acid within the lemon. If there is no completed circut then the galvanic action does not take place.

    The potental is there but until the circut is completed there is none.

    Both brass and steel will independently react to the action of the acid. Even together within the same tub but not touching, they will react independently. But put a wire from one to the other outside of the bath and you then have a completed circut, and will see sevear wasting of the less nobel metal.

    lance
     
  7. Bom Bom Bom Bom

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    Ah, OK, see what you're saying. As John was originally talking about his Valor stove where the steel legs are soldered to the tank I assumed you were talking about the same set-up.

    Cheers, Graham.
     
  8. John Leah

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    As the only time I'd need to have both metals in the same solution is when they are inseperable - so touching - are we saying this is a bad idea?

    Cheers,
    John
     
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  9. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi John, you don't need to immerse dis-similar metals in Citric acid solution. Check out this post, and then just use GSR = Wallpaper paste plus citric acid:

    https://classiccampstoves.com/threads/3963

    Best Regards,
    Kerophile.
     
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  10. John Leah

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    Very good article Kerophile, I'll certainly give it go, thanks.

    Cheers,
    John
     
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  11. Lance

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    John my first attempt with vinegar i put both in at the same time. Steel turned black, brass cleaned up okay. Mind you they were in there overnight. I don't believe i'd do it again but back then i was young and stupid, and got lucky it worked. Pictures are in the old forum.

    lance

    Be nice Doc, and i'll agree i was young. Okay, younger, would you believe that?????
     
  12. David Shouksmith

    David Shouksmith Subscriber

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    I find cheap vinegar very effective, although it stinks, most especially when it's been used a few times. Overnight is far too long and you'll find the zinc leaches out of the surface of the brass, leaving it with a pink copper coating which is a major pain to remove.

    Immerse for no more than 20-30 minutes at a time, rinsing and wiping thoroughly between immersions to remove the loosened crud, otherwise it forms a barrier and prevents the vinegar getting to the metal underneath. Repeat as necessary. Works for me... :thumbup:
     
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  13. Lance

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    Right you are David. It was my first attempt and i was thinking it would need a long soak to do what i expected. Lucky for me the vinegar was a weak solution, i cut it about 50/50 with water. It did the job but wow did my stuff look wieard.

    lance
     
  14. fyldefox

    fyldefox R.I.P.

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    It's also a good idea to wash it in hot washing-up liquid first as this removes a lot of grease and crud and helps the vinegar / citric even more.
     
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  15. Bom Bom Bom Bom

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    And if you are doing burners perform a heat and quench cycle first as that also removes a lot of the burnt on carbon deposits from the outside of the burner. The citric acid bath will then bring a burner up to almost like new (ish) without too long a soak. If doing burners also don't forget to thouroughly flush out the insides of the burners with clean water when finished (same for the inside of tanks).

    Cheers, Graham.