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Stove restoration. Parts 1 to 4

Discussion in 'Fettlers Master Class' started by kerophile, Aug 27, 2006.

  1. kerophile

    kerophile United Kingdom Subscriber

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    Hi, this Part should have been covered before the lacquering but some readers were just too impatient!

    Ironwork


    1. The following remarks refer mainly to Brass stoves although they do have a wider relevance.


    2. The term "Ironwork" in the title refers mainly to the steel commonly used for the legs, and sometimes the feet of stoves, and to the pan-rings (aka pan-holders or trivets).
    Steel was also sometimes used, mainly on British and French post-WW2 stoves, for the flame spreaders and spirit cups.


    3. The legs ( and feet when steel was used) were "tinned" with solder at the manufacturing stage to aid assembly of the stove and provide corrosion protection in service.


    4. Providing this "tinned" layer has not broken down, it is relatively easy to recover the original finish of the legs, by soaking them in solvent degreaser, or a strong detergent solution,and then scrubbing with a Scotchbrite pad, to remove carbon deposits and other crap.


    5. It is a good idea to follow the above procedure whatever the sate of the legs, steel feet or pan-holder as it will reveal their condition and prepare them for further treatment. If it is a collapsible stove that you are working on the legs can be removed and this makes the work much easier. If you have a fixed leg stove things are a bit more challenging.


    6. If there has been significant rusting of all, or part, of the legs the first thing that needs to be done is to remove the loose rust deposits and then halt the corrosion process. Wire brushing and abrasive cloths can be used but be careful to avoid pulling off the legs or damaging the adjacent soft brass of the tank.


    7. Pan-holders can be very rusty so they are prepared in similar way to that described for the legs.


    8. A number of patent "rust cures" or treatments are marketed. In the UK, Kurust, Jenolite , and Hammerite all spring to mind. There will be equivalent products in most countries of the World. They can be good products and if you follow the instructions they will "Kill" the existing rust and provide a surface suitable for finishing, for example by painting.


    9. Alternatively you can folow my example and "brew" your own "Rust Killer". If you can obtain concentrated Phosphoric Acid and arrange to have it slightly diluted ( 85% Acid to 15% Water) you have a very effective product for less than £5 a litre....and a litre goes along way.


    10. HEALTH WARNING:
    a) Wear Goggles, Rubber Gloves, Eye Protection,and a rubber apron or old clothes.


    b) Remember to add acid to water if mixing solutions, never the other way around!!!


    c)Do not carry out rust removal operations in the house or in a confined space because
    of the fumes.


    d) work in a plastic basin or similar container. Phosphoric Acid will react with concrete, fabrics, human flesh, etc.


    Most of the above is common sense and this is not a particularly hazardous process but I thought I would write it all down as I don't want you partner/ wife/ lover/ Mother bitching to me if there is an accident.



    11. Do NOT immerse the whole stove in this mixture! It will certainly remove tarnish from brass but citric acid is cheaper and more controllable. All dirt,flaking rust, and paint should have been removed from the steelwork as described above. It is easier to paint the Rust Killer onto the legs or panholders rather than to fully immerse any part of them.


    12. The acid mixture should not harm the solder holding the legs to the tank, or any residual tinning on the legs, but if you see it "fizzing", wash it off and be more careful with the application next time.


    13. I recommend that you leave the Rust Killer coating on for at least a couple of hours. In this period you should ensure that any particularly rusty areas stay well coated.At the end of this period remove any un-reacted liquid using Methylated Spirits or alcohol. Once the alcohol has evaporated, allow the surface to dry. It is then ready for lacquering or priming and painting.


    14. For the more technically minded: Phosphoric acid , when used to treat iron and steel, produces a so-called "Conversion Coating". It converts certain poorly adherent iron oxides into a hard, black. adherent iron oxide ( Magnetite). There are also Phosphates in the converted layer.This black layer will inhibit further corrosion ( rusting) providing it is protected by a lacquer or paint system . Typically phoshate- treating steelwork prior to painting more than doubles the life of the paint system.


    15. Whether you use paint or lacquer for finishing depends on personal preference. I tend to lacquer the legs and paint the pan-rings. If you intend to use the stove, use a heat-resisting paint on the pan-ring. Alternatively, one of the bear-grease and salt recipes, used by some people to "season" iron pots and Dutch Oven before use, can be tried


    16. I also use Rust Killer on stove boxes to halt the worst ravages of corrosion and rusting... but be careful how you apply it as it can darken or remove paint finishes.


    17. The 2nd Health Warning: The information in this post is believed to be accurate and is given in good faith. If anyone sees any technical error(s) let me know as soon as possible and I will rectify.
    If you decide to give it a try, be sensible , use personal protection and don't drink the priming sprits beforehand.


    Good Luck with your stove restoration
    Regards,
    Kerophile.
     
    Last edited by a moderator: Jun 27, 2015
  2. David Shouksmith

    David Shouksmith United Kingdom Subscriber

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    :-k I may be wrong here, George, but I'd always understood the black coating was primarily iron phosphate...
     
  3. kerophile

    kerophile United Kingdom Subscriber

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    Hi David
    ...You are wrong.
    Best Regards,
    George.
     
  4. David Shouksmith

    David Shouksmith United Kingdom Subscriber

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    :) I realise I'm on dodgy ground here, discussing such matters with a metallurgist, but the literature seems to suggest it's iron phosphate, for example :?
     
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  5. Jan Merx

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    Nice info, George. Certainly something for future reference.

    So far, I have resorted to cleaning up rusted steel as far as i could, then use touch-up gun-blueing. Quite pricey, really, but it does the job. Very heatproof, too.
    I get a faint idea, that the gun-blue is using phosphoric acid as well, but has some other chemical added to create that bluish hue. Am i right?

    I once used baking grease and the kitchen-oven at high temperature to treat all rusted metal parts on a Phoebus 625. It's holding up just fine after 3 years and fair use...
    It just stinks up your kitchen really bad and the surface looks not even. A bit brownish-black in color.

    My 0.02EUR dispensed.
     
  6. kerophile

    kerophile United Kingdom Subscriber

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    Hi David, thanks for the link to the abstract of the Technical article.

    I find that the older I get the more I realise how little I really know.

    However, phosphate treatment is a very complex process...... and it all depends;

    It is certainly easier to say to a lay-man that phosphate treatment produces an iron phosphate surface layer, but the practical situation is very much more complicated

    In carefully controlled laboratory conditions with good pre-treatment of the steelwor, and tightly-controlled bath conditions, it may be possible to get essentially full conversion of the surface layers to iron phoshates.

    In the real world, with existing iron oxide layers, you are more likely to get a whole range of compounds and I would suggest that with stove components and room temperature treatments, it is likely that black, adherent magnetite (an oxide of iron) dominates.

    Best Regards,
    Kerophile
     
  7. David Shouksmith

    David Shouksmith United Kingdom Subscriber

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    I bow to your superior knowledge, George... ;) :lol:
     
  8. Madhiker

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    Wandered in here on a cold icy night with an embarassingly neglected 123. Suppose there will have to be a before & after set of spectacular photos after reading this thread. (They really should have blackened the aluminum at the factory, much faster boiling time)
    Pass the dremel :shock:
     
  9. Bantamite

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    Hi. I Googled the Joy paint company, but have not found anything. Any suggestions for a UK outlet for this or a similar lacquer please?
     
  10. kerophile

    kerophile United Kingdom Subscriber

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  11. Bantamite

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    Thanks for that Kerophile.
    I am fortunate in having two ironmongers/hardware shops not too far away (one is more garden stuff), so will give them a try for that.
     
  12. Robert Bruce

    Robert Bruce Australia Subscriber

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    A question about citric acid, I have been using it for ages. I keep it mixed with water in a plastic bucket with lid. When after a wile with no use it gets some mold floating on the surface, usually I scoop it up with a cullender, it works well although it's discoloured with gunk.
    Is there any way of stoping this mold? It still works just as well kept for ages. Should I not be conserned about the mold or put something in it to stop it? Chlorine would stop the mold but mixing it with an acid is a no no. Is there anything else that would be fine?

    Cheers
    Rob
     
  13. kerophile

    kerophile United Kingdom Subscriber

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    Hi @Robert Bruce , I am no biologist but understand that essentially all Citric Acid in now produced industrially by feeding sugars to black mould. The citric acid made by the mould is extracted, purified, and sold. So it is not surprising that some mould species' spores, carried in the air, can grow and thrive in certain low concentrations of citric acid.

    In medicine, where citric acid is used in some cleaning solutions mould growth had been reported as a problem in some situations (dialysis). Unused solutions are therefore disposed of after a few weeks storage and the container cleaned with chlorine solution before being rinsed and refilled.

    I have never had a problem with mould in citric acid solution at concentration of about 2 teaspoonsful per pint. However my solutions are green with copper salts after use, and should kill most moulds and slimes.

    I favour GSR, cellulose wallpaper paste with detergent and citric acid, for most applications. It is single-use but I have never seen mould in made-up GSR paste stored in pump-dispenser bottles.

    Citric acid is relatively cheap in the quantities stove restorers use, so periodic replacement of solutions is probably a good practice.

    Best Regards,
    Kerophile
     
  14. Jeopardy

    Jeopardy United Kingdom Subscriber

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    Hi @kerophile most wallpaper paste that I've ever seen contains fungicide so I'd be worried if you did see mould in your stored GSR.

    @Robert Bruce To keep citric acid solution mould free you could try adding some sodium benzoate otherwise known in Europe as E211 because it is used as a food preservative in acidic conditions. Sorry but it's 30 years since I used it for a similar purpose in a lab and I've forgotten what concentration you'd need..... but it wasn't much

    Regards
    John
     
  15. kerophile

    kerophile United Kingdom Subscriber

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    Hi John, thanks for the information. i do now recall the mention of fungicide in wallpaper paste.
    Regarding the use of Sodium Benzoate as a mould killer, the effective concentration is low, as you say, and the Wikipedia entry lists 0.1 wt. percent as the maximum content for foods intended for human and pet consumption:

    https://en.m.wikipedia.org/wiki/Sodium_benzoate

    You learn something every day on CCS!

    Best Regards,
    Kerophile.
     
  16. Robert Bruce

    Robert Bruce Australia Subscriber

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    Thanks Kerophile on the citric acid. I think for now I will ditch it as it's been used for ages. It's really muckey. Next time I will try some food preservative but in all reality with the price of citric acid being cheep I may just use it a couple of times and ditch it. Interesting information though .

    Cheers
    Rob
     
  17. Robert Bruce

    Robert Bruce Australia Subscriber

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    Oh yes, the wallpaper glue mixed with citric acid just may be better, may give it a go next time.

    Cheers
    Rob
     
  18. Benzin Croatia

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    About vinegar, citric acid and other stuff that make brass go pink. If your brass parts went pink this is not a problem. Brass is an alloy of copper and zinc and it is complete nonsense to think that zinc makes a film over brass and that they mix in layers. Brass is an alloy and acid will only take the copper out on the surface.

    This process can be easily reversed. Mix 50ml Hydrogen Peroxide with 100ml of White vinegar and enjoy your golden brass color return completely. After everything becomes golden it is up to you will you polish it to flashing or keep it matte. So don't worry, nothing is lost.

    Regards,
    Benzin
     
  19. kerophile

    kerophile United Kingdom Subscriber

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    Brasses go pink as a result of de-zincification, or preferential removal of zinc, from the surface layers of this copper/zinc alloy. In the acid systems we are discussing it is an indicator that the oxide layer/patina has been dissolved, and the bulk metal is now being attacked. Time to stop the reaction!
    The surface pink colour can easily be removed by light polishing.

    Benzin's suggestion involves an alternative chemical method of treating the metal surface, incidentaly with a solution that really stinks.

    "Niche uses
    Peracetic acid will oxidize many metals, and is used for cleaning or creating a patina for artistic or protective purposes."

    The above extract comes from a Wiki entry:

    https://en.m.wikipedia.org/wiki/Peracetic_acid

    Make your choice:

    Best Regards,
    Kerophile.
     
  20. kerophile

    kerophile United Kingdom Subscriber

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