[meteorite-list] Experiment Update #1

[Norm Lehrman]

Göran & all,

I don't understand the chemistry involved, but I have
personally used a concentrated sodium hydroxide bath
to remove rust from very rusty Campos.  It took weeks,
but scales of rust just kept detaching untill the
bottom of the pail was a centimeter deep in rust
flakes.  I did do a final treatment with a wire brush,
 but ended with a beautiful metallic specimen.  This
treatment wasn't just a rust stopper.  It removed rust
in large quantities.  The solution didn't discolor as
if iron was being dissolved.  Flakes just popped off
and fell to the bottom.

Cheers,
Norm
http://tektitesource.com

--- Göran Axelsson <axelsson at acc.umu.se> wrote:

> This is not a rust cleaner treatment, it is a rust
> stopper treatment.
> 
> To remove the rust you have to use more traditional
> methods, like polishing.
> 
> Acidic solutions with a low Ph makes it easier to
> dissolv the iron 
> hydroxides in rust but at the same time the iron
> will be unprotected 
> against oxidation. Basic solutions with a high Ph
> stops the iron 
> hydroxides to dissolv but protects the iron against
> oxidation by 
> passivation, it becomes chemically inert.
> 
> The idea behind the hydroxide solution is to protect
> the iron while 
> chloride ions are leached out of the meteorite.
> 
> I would recommend small volumes in the bath, maybe
> twice the volume of 
> the meteorite but at least covering it, combined
> with numerous 
> replacement of the solution. In the beginning it
> should be closer 
> between the changes of the solution as it faster
> gets contaminated. When 
> the chlorine levels in the meteorite and the
> solution is in balance it 
> doesn't help to let it lie longer.
> 
> Archeologists sometimes uses ordinary tapwater in
> the initial bath but 
> at the end they use deionised or distilled water.
> 
> And whatever you do, don't use chlorinated water,
> that could make it 
> rust even faster.
> 
> /Göran
> 
> tracy latimer wrote:
> 
> > About 10 days ago I dunked my poor Fredericksburg
> in what I hoped 
> > would be a rust removal bath of half Liquid Drano
> and half anhydrous 
> > alcohol.  Since then, I have swirled it about at
> least once a day, and 
> > some of the rust has come off, but not all.  The
> bath is lightly 
> > tinged with brown and there is a fine peppering of
> rust flakes on the 
> > bottom of the glass jar.  I will give it another
> week or so, but if 
> > there is not a significant change in the quantity
> of rust in 
> > suspension rather than on my meteorite, Freddy
> will be taken out of 
> > the bath and more old fashioned methods of getting
> rid of rust will be 
> > regretfully employed.
> >
> > Watch this space for more fast-breaking news!
> > Tracy Latimer
> >
> >
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