Removing heavy rust from enamelled hoods

Discussion in 'Fettling Forum' started by MYN, Sep 13, 2018.

  1. MYN

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    Hi all,
    I posted this to find out on the ways that you guys use to remove heavy rust from chipped enamelled lantern hoods.
    Much earlier, I've made a mistake of overrating the porcelain-enamel coatings on steel.
    I thought they were no different from the actual porcelain on ceramic wares, expecting they're highly resistant to acids.
    Therefore, I immersed a chipped and heavily rusted hood(most of the enamel were still intact) of an AFM 1967 milspec lantern in a concentrated citric acid solution for a couple of days. When I retrieved it, the previously gloss enamel surface had actually dulled and discoloured.
    The reason I did that was because most of the rusting was on the inner side of the hood and its hard to reach or clean out by mechanical means.
    I was pleased that the rust was completely removed down to the tiniest pits and crevices, but completely dismayed by the dulled hood.
    So guys, are there any better ways of doing this without harming the porcelain enamel?
     
  2. Wim

    Wim Subscriber

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    Hi @MYN , I have not yet tried this myself, but maybe electrolysis could be an answer to this problem. Best tried out on a badly damaged one to be safe!

    Best regards,

    Wim
     
  3. Matty

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    You could have inverted the lamp and filled the inner hood with your solution.

    I do this with lamps with steel bottom founts when the plating is too good to risk putting in vinegar for too long.
     
  4. MYN

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    For electrolysis, I'll need to attach the lead wire with good ohmic contact to an exposed part of the hood, which might pose a problem if the only exposed area is on the inner side of the hood.

    What about other solutions to this?

    At the moment, I'm trying out one of Matty's favourite - Vinegar immersion. Just found out that it does not significantly attack the enamel like other acids do.
     
  5. Matty

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    @MYN,

    Vinegar will attack and dull the enamel if left too long. I think it is fine to leave enamel in vinegar in short bursts but definitely not overnight type thing.
     
  6. MYN

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    I'll note that, Matty.
    I couldn't get my hands on those chelating and complexing cleaning stuffs such as Evapo Rust, EDTA, etc. I'll reckon that those would be less aggressive and not caustic.
    I would have just scrubbed off the rust if thèy are accessible.
    I've tried phosphoric and oxalic acids but these are even more aggressive than citric acid.
    The other stuffs I have in my arsenal are concentrated sulphuric, hydrochloric acids as well as stainless steel pickling gel which contains hydrofluoric and nitric acids. These, without doubt, would completely destroy the hood.
     
  7. Matty

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    @MYN
    Did you see my post about inverting the hood? You just need to find a place and place the hood on an old rag and use the rag to tuck under the hood to get it quite level. Then you just fill up the hood to the very brim and let it sit for a couple of days.

    If you need to, use some Blu Tac from the enamel side, to plug any holes associated with the hood. Any sort of pliable putty that is easily removed would work. Perhaps even some masking tape.
     
  8. Tony Press

    Tony Press Australia Subscriber

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    @MYN

    I have one very beaten up Tilley hood, with remnant enamel.

    I’ll test a chelating agent on it and see how it turns out.

    Tony
     
  9. MYN

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    @Matty,
    Yes. I've read about inverting the hood. The problem is: both the inner and outer sides are enamelled, chipped and rusty. I might as well dunk the whole hood into a container of vinegar.

    @Tony Press
    Its great that you have access to those chelating agents.
    Not in my case.
     
  10. Reese Williams

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    I would avoid electrolysis on an enameled vent. I suspect it might loosen the good enamel. As you've found, acids tend to dull the finish. I've had good luck with a chelating agent, in particular Evaporust. I simply immersed the vent in a plastic bucket, covered the bucket and left it. As I recall I have forgotten about one and left it for a couple of weeks with no ill effects.
     
  11. MYN

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    @Reese Williams
    The Evaporust. That's what I couldn't get easily here.
    BTW, does anyone know how to brew up some similarly chelating mixtures from common everyday stuffs?
     
  12. ColinG

    ColinG United Kingdom Subscriber

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    As @Reese Williams already said, electrolysis will probably try to lift the enamel, most likely at the edges of the rusty areas, so not advised.
     
  13. MYN

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    Thanks Colin.
    The vinegar(5% acidity) seemed to do the job well enough without harming or dulling the enamel.
    Its was rather slow. I had to immerse the hood for at least three days before most of the rust could be removed.
    I would not have such patience if its not for the enamel. I've got plenty of fairly concentrated muriatic(hydrochloric) and sulphuric acids ready at hand.:p
     
  14. David Shouksmith

    David Shouksmith United Kingdom Founder Member

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    :shock: They're mineral acids as opposed to organic acids such as acetic and citric. Use them on ferrous metals at your peril - or even brass come to that... =; :whistle: :doh:
     
  15. MYN

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    Of course not on an old delicate lantern, David:)
    They're some leftovers from my previous works on removing mill scale and heavy rust from large pieces of structural steel channels. I would have some neutralization done with caustic soda and plenty of water rinsing, drying and subsequent measures of preventing flash or re-rusting.
    The strongest mineral acid I've used for certain lantern parts is phosphoric acid. Even this can be too aggressive for comfort.
    The previous two had costed me numerous skin removals and renewals instead. That goes for the caustic soda too=;
     
  16. David Shouksmith

    David Shouksmith United Kingdom Founder Member

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    Not on any lantern, surely...

    Phosphoric acid should be OK given it's the active ingredient in most rust stabilisers. It converts rust to stable iron phosphate which can be overpainted...
     
  17. Mendoza603 United States

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    Hi guys

    I will recommend this product.
    To whoever want to try it.

    This produc get the job done in minutes.

    Clean the black burner in a couple of
    minutes. (When I say minutes is in one or 2 minuets) immediatelyyou put the part inside the the product, you will see the resort) I don’t think will damage your porcelain code because is for use on bathroom.

    Please let me know what you think.


    ///Fernando
     

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  18. MYN

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    It contains hydrogen chloride which is basically hydrochloric acid if in aqueous form. Of course it will remove rust.
    But at 9.5%, maybe its still ok, provided you don't leave it too long on the enamel.

    Bathroom enamel is a ceramic glaze with a somewhat different composition from the vitreous enamel coating on steel.
    I wouldn't know about the difference in their chemical resistance.
     
  19. JonD

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    Don't think the issue here is so much the enamel. It's more about what is underneath.
    The glass enamel (or what else) is applied to hopefully clean metal - all well and good when new.

    Get a chip or a crack due to impact or heat - water will get in and the pure metal starts to rust and worse that spreads out - maybe invisibly.
    It is separating enamel from metal and nothing can put that back.

    Like in metalwork filing lessons the "putting back on file" does not exist. Unstable enamel has to come off. Rusty metal underneath can only be stopped from rusting any more (much).
     
  20. MYN

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    @JonD
    Yes, true. If the rust has spread underneath the enamel, there's nothing much we can do other than remove that enamel layer too.

    But there are still those with most of the enamel still intact without the 'under layer' corrosion, but a few chipped areas where the rust is heavy.
    These are the ones where most of the rust could still be removed and the exposed steel areas to be then protected from further corrosion. (Besides re-enamelling).
    Its not particularly easy to further protect those that would continue to be used as workhorses since there aren't many paints that would stand up to the heat.
    I'll usually surface treat those so that there's at least some black/grey oxides or some other chemically-bonded heat resistant compounds that should greatly slow down the rate of rusting(the red type of rust). However, these would not be very corrosion resistant if neglected/unused and allowed to get moist frequently without a layer of oil or wax.
     
  21. JonD

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    @MYN I follow your reasoning.

    When I was quite young (12-13?) my school did some enamelling with glass beads on clean steel discs in a very fierce little kiln. It was driven by electricity I suppose but not sure.
    It worked out very well for me but I have lost the results after 40 years or more.

    You make me think that if you could grind away bad enamel areas back to base metal, and maybe a bit further than that, and <if> you had the right glass beads, perhaps some repair would be possible.

    I do not have any access to what is required. Maybe someone else has tried?

    I have an oxy-acetylene torch. That can convert rust back to metal with a reducing flame but it is imprecise. Rust> metal balls is the usual result rather than fused in the surface as you would like.

    They don't let school kids do this anymore. A great pity.
     
  22. David Shouksmith

    David Shouksmith United Kingdom Founder Member

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    The composition you require for vitreous enamelling is called frit so there's your start, anyway - i.e. first find your frit...

    Frit - Wikipedia
     
  23. MYN

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    @JonD
    Sure it would be nice and interesting if anyone could re-enamel the hood at home.
    I don't have the expertise for that. It might seem as simple as fusing a frit coating on steel with a kiln or furnace of some sort.
    But I believe its not as simple as it sounds. Having the right frit-mix composition is one thing. Having suitable equipment/setup to heat up uniformly to fusing temperatures within a well-controlled environment is another.
    Its not just melting powdered glass on steel. I don't think it'll adhere on the surface like the way we wanted.
     

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