[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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