[meteorite-list] Rusting S-As/Protecting irons

From: Steve Schoner <steve_schoner_at_meteoritecentral.com>
Date: Thu Apr 22 10:14:08 2004
Message-ID: <20030429152757.50724.qmail_at_web12705.mail.yahoo.com>

--- Howard Wu <freewu2000_at_yahoo.com> wrote:
>
> If I remember my chemistry Ag ions trap Cl ions.
> Perhaps AgNO3 is the answer for rusting disease. Of
> course that will silver plate those irons.
> Howard Wu
> "E.L. Jones" <jonee_at_epix.net> wrote:Good Answer
> Dave. You don't have to live by the sea to have
> rusting irons.
>
> Be it remembered, that it is the chlorine ion which
> is the rusting
> facilitator. The most common source is via salt
> (NaCl) from the skin.
> It acts as a catalyst by holding the slightest
> amount of moisture from
> the atmosphere.( Under the microscope these droplets
> look like little
> brass or bronze colored insect eggs. The Chlorine
> ion will NEVER
> evaporate and until it is physically removed it will
> trap the oxygen
> molecule against the iron atom and do its nasty
> magic--over and over and
> over. "Handled unprotected once; contaminated
> indefinitely".
>
> Regards,
> Elton
>
>
> Dave Harris wrote:
> >
> > They reside, unprotected, in my mineral cabinet
> and, as far as I know, have
> > not been treated in anyway except being lovingly
> fondled. Two of them are
> > original' ex- Russian Academy of Science specimens
> and they have a natural
> > patina - maybe not as nice as some I seen (like
> Martin's chocolate beauty)
> > but still are splendidly tactile!
>
>
>
>
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Actually,

It is not NaCl that is the reason. And the rusting
disease does not originate from the hands. Salt, in
and of itself is very mildly hygroscopic, and the bond
between Chlorine and Sodium is strong.

The problem is FeCl3 and NiCl2.

The Cl does come from salt over a long period of time,
and this in a meteorite can lead to "iron cancer" the
process that ferric and nickel chlorides start. The
Cl starts a catalytic action, and jumps from iron atom
to iron atom until the free iron is converted to rust.

Unlike NaCl, FeCl3 and NiCl2 are extremely hygroscopic
and readily absorb water from the air. For NaCl to
form free ions it would have to be in the direct
presence of water, or extremely humid ocean air. But
FeCl3, and NiCl2 will take the water right out of even
the driest air to form those greenish brown blebs on
meteorites that have been weathering for a long time.

Get rid of FeCl3 and NiCl2 and the rusting problem
will be solved.

(And you can fondle your meteorites forever after)

Steve Schoner
http://www.geocities.com/meteorite_identification
http://www.geocities.com/american_meteorite_survey


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Received on Tue 29 Apr 2003 11:27:57 AM PDT