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Thread: _ The Black Stuff after Home-brew electrolysis rust removing.

  1. #1
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    Question _ The Black Stuff after Home-brew electrolysis rust removing.

    Sorry, forget the correct name of 'The Black Stuff' that is "created" after a basement electrolysis session.
    Is is paint able or does that too have to be removed and if removed, whats the best way to approach it ?

    I have a NO. 3-1/2 arbor press which i might try electrolysis on. The Quill, base - all moving parts are rusted and not functioning. If the electrolysis session frees up the moving parts, i will then take everything apart and and clean the components, but as for the body/housing, i really dont want to deal with cleaning it a second time, would be nice if i could just paint right over the 'The Black Stuff' or just leave it Black.

    Heres a link and story to the press:
    http://bbs.homeshopmachinist.net/thr...s-30-years-ago


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  2. #2
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    Sounds like the Fe2O3 is being made into magnetite, Fe3O4, but that's a guess!, I spent my time doing it the other way in steel making, I'm not sure if it's good to paint myself, a coat of the rust stabiliser might be a good idea.
    Mark

  3. #3
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    I have done a number of iron hand planes and once they are finished in the spooge spa I simply rinse with water and some Scotchbrite and then wax. I see no reason you could not clean, dry prime and paint.

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    I REALLY like that "simply rinse and some scotchbrite".

    Reminds me of the hyper-organic gardener recommending "hand picking" destructive pest insects, when you are standing looking at 500 acres of corn....

    I found that the "black shell" created by electrolysis was extremely durable, and very difficult to remove without an amount of effort nearly the same as the effort needed to remove the rust by hand brushing methods. And that is why I only tried electrolysis a couple times, and will never again bother with it.

    The only removal method I found to work on the black stuff is by hand, using intense brushing with a wire brush, or similar.
    1601

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    Hashim Khan

  5. #5
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    I'm curious what would happen if you tossed a few large rare earth magnets in the water when you "electro-boil" it. Any chance the "black" stuff would adhere to the magnets vs the part being de-rusted?

  6. #6
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    Quote Originally Posted by J Tiers View Post
    I REALLY like that "simply rinse and some scotchbrite".

    Reminds me of the hyper-organic gardener recommending "hand picking" destructive pest insects, when you are standing looking at 500 acres of corn....

    I found that the "black shell" created by electrolysis was extremely durable, and very difficult to remove without an amount of effort nearly the same as the effort needed to remove the rust by hand brushing methods. And that is why I only tried electrolysis a couple times, and will never again bother with it.

    The only removal method I found to work on the black stuff is by hand, using intense brushing with a wire brush, or similar.
    Just kidding but you really come off as an electrolysis "hater".
    The loose black stuff will mostly rinse of under a stream of water. I usually dry the parts in the oven. Whatever amount is left provides a firm base for painting. One or two times, I did get a hard black finish, almost like plating, didn't rub off on your hands. Unfortunately, haven't been able to replicate those results.

  7. #7
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    Quote Originally Posted by J Tiers View Post
    I found that the "black shell" created by electrolysis was extremely durable, and very difficult to remove without an amount of effort nearly the same as the effort needed to remove the rust by hand brushing methods.
    I have used EDR for several years and believe in it. I think that what you ran into is common. The technique I use is to remove the workpiece -- and don't forget to turn off the power supply before touching the wires -- and scrub lightly under hot water. Then if the part is as you describe, simply put it back in again. And make sure you have an anode near the hard black areas.

    metalmagpie

  8. #8
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    You may be compelled to bead blast. If done judiciously there will be no erosion to the base metal. That said electrolysis does not restore. It only changes chemical state. The surface may be deoxidized but the spongey crust left behind will never be sound metal again.

    The as-cast part of the press need only vigorous wire brushing to remove loose material then painted. The machined part will be as it is. It may be that de-scaling and blasting be required then repair brazed and re-machined. Tapped holes may need to be plugged and re-tapped. You may have to make another rack and pinion. It all depends on how deep the corrosion went and what defects in fit you can tolerate.
    Last edited by Forrest Addy; 12-23-2014 at 12:45 PM.

  9. #9
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    The "hard to remove" black coat (not the easy to wash off stuff with scotch brite and water) is magnetite, and a great tough base to paint over.

    Magnetite formation will depend on what form the oxide already is, and... your current density. Very low current density (a few milli amps per square inch) will reduce formation, but you need a lot more density to blow off paint etc. Museum restorations or old cannons etc use micro amps per square inch... and can take a year to remove the corrosion while leaving behind very fine inscriptions. You probably want to get this done in day or so, so...

    This is another reason to use a constant current power supply. To keep current density where you want it, a constant voltage supply will require your continuous attention. But.. even constant current will not guarantee a fixed current density unless you have a good idea of where the current is actually flowing - paint, anodes and shadowing effects all come into play.

    If it was mine... for this size item I'd crank up the current to 15-20 amps or more for a say 8 hours, take it out and clean off the paint (It will just fall off) and any loose stuff (and the anodes) , then put back in a 2-5 amps for a day then clean off and wash in hot water. A light coat of phosphoric acid will kill any flash rust.

    DON'T run high current in a basement... hydrogen gas, foam, mess etc.

  10. #10
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    I have used electric derusting several times and love it. The black "stuff" for me comes in two varieties. Slimy, soft easily removed with a scotch bright and some soap.

    And the hard as heck black stuff left AFTER cleaning the sludge. That stuff usually stays in place for me and primed and painted. If the hard black stuff is a lil lumpy and bumpy in texture I can usually break it down a lil with some abrasive sheets. JR

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