[TheForge] Electolytic rust reclaiming

Tue Oct 29 14:02:00 2002

I'm no expert on this.  I'm only applying my knowledge of chemistry.

Iron III oxide is red.  Iron II oxide is black.  Rust is iron III oxide, =
Fe2O3.  Scale is iron II oxide, FeO.  I SUSPECT the black is FeO.

If the rust on the ways is light, then any ordinary rust removal technique =
should leave a good machine.  If it's heavy, nothing will help.  Possibly =
there's some way to fill rust pits on machine parts (equivalent to solder =
or Bondo, but with some strength to it) but that's a question you'd have =
to address to a restorer of machinery.

I can't see how electrolytic rust removal would be detrimental, but if I =
were you I'd look into getting some sodium or potassium phosphate =
(monobasic) and using that to clean off the rust.  Mixed with water, this =
should produce a solution of pH ~5.  Should be acid enough to take off the =
rust. The phosphate is reputed to protect against further rusting.   Wear =
gloves and goggles.

Anything you do, degrease the surface first.

Bruce
NJ

>>> [email protected] 10/29/02 12:22PM >>>
Ok...now we are back to where this question started, I too questioned
that the "converted" metal was "back to" steel/iron.  What is the
resulting composition of the "black metal" that this process leaves?
I believe you are correct that the process is done with the negative
on the piece and positive on the anode, something I'd be sure to check
before I applied any voltage.

   The reason I'm asking is that a friend has some equipment that he
has allowed to rust somewhat.  I want to do the electrolytic
conversion on the ways of the machines,  but not if it won't be solid
when I'm done.

    Thanks!

   Jeff   ><>

----- Original Message -----
From: "Bruce Freeman" <[email protected]>
To: <[email protected]>
Sent: Tuesday, October 29, 2002 11:52 AM
Subject: Re: [TheForge] Electolytic rust reclaiming

> Although in principal, you could electrically reduce rust back to
iron, in practice it is not likely to work this way.  If you ever
succeeded in reducing the rust to iron, you'd have a layer of scaly
iron on top of your steel - it would NOT be steel you got back, and
the alloy composition could be anything and may depend upon the
voltage applied.  The major obstacle to this happening is simple
electrical conductivity - steel conducts, rust probably does not.
Hence the electrolytic reaction cannot occur in the rust because there
is no electrical conduction to make it happen.
>
> A rust to steel conversion would also require that the object be
connected to the negative electrode.  I don't recall whether that's
what's done or if the reverse is done.  I suspect it IS done, and the
reaction proceeds just far enough to convert the layer of rust on the
surface of the metal (not the surface of the object) back to iron, at
which point all physical contact is lost to the rest of the rust,
which then falls off.  That part is just speculation, however.
>
> Bruce
> NJ
>
> >>> [email protected] 10/29/02 11:35AM >>>
> Hi all...
>
>    I asked a guy I know that is one of those people that remembers
> everything he ever read and actually understands things in the more
> abstract, "theoretical" way.  He's even good with his hands, though
> not likely to ever make "flat rate".  So...this is what he said is
> happening.
>
>    When iron oxidizes it absorbs oxygen, as it does it "bubbles up"
> leaving the rust and pits we are all familiar with.  He says that if
> you controlled a rusting piece of iron so that none of the oxide is
> lost, the final pile of iron oxide would weigh more than the
original
> piece of iron.  The electrolytic conversion removes the oxygen from
> the iron oxide leaving it in it's original chemical composition.
>
>    The bubbling up of the metal however is not changed, so now the
> de-oxygenated metal is not as solid as it was, it retains it's
> porosity.
>
>    Anyone?
>
>    Jeff   ><>
>
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