AW: [meteorite-list] How I (mis)treated my Brahin

From: Jörn Koblitz <koblitz_at_meteoritecentral.com>
Date: Fri Jun 17 07:43:33 2005
Message-ID: <492FFD0696089A4CB72BDBDCB2FC1A14029AE7_at_server2000>

Hello G?ran,

> I bought a Brahin slice about eight months ago. When I got it it was already
> rusty even though it was sealed. The rust were everywhere under the lacquer
> and had even seeped through and stained the paper it was wrapped in.

If the specimen prepared this way wasn't well dried before coating with lacquer, it will worsen the situation as water gets trapped within the cracks and can form a perfect acidic mini-environment for fast corrosion, especially if salts are present.

BTW: Be careful with electrochemical cleaning as any rust present will be converted or dissolved. This may course olivines falling off the specimen. You may have to fix the olivines with an (alkaline-stable) resin. Its tricky. The best is to do such things BEFORE a meteorite has started to disintegrate.

Best wishes and good luck,
J?rn


> -----Urspr?ngliche Nachricht-----
> Von: meteorite-list-bounces_at_meteoritecentral.com
> [mailto:meteorite-list-bounces_at_meteoritecentral.com]Im
> Auftrag von G?ran
> Axelsson
> Gesendet: Freitag, 17. Juni 2005 13:26
> An: meteorite-list_at_meteoritecentral.com
> Betreff: [meteorite-list] How I (mis)treated my Brahin
>
>
> I bought a Brahin slice about eight months ago. When I got it
> it was already
> rusty even though it was sealed. The rust were everywhere
> under the lacquer
> and had even seeped through and stained the paper it was wrapped in.
> It was also broken in three pieces in the freight.
>
> The seller told me it wasn't rusty when he sent it. It was
> hard to belive
> but I let it rest and thought it was what you had to pay to learn.
>
> What to do? Well, I stripped the lacquer on a test piece by
> sanding it. Then
> I polished it again by hand (in isopropylic alcohol) and
> dried it in the
> oven
> at 70 degrees celsius for a couple of hours.
> It's now been without any protection on a shelf for over six
> months, handled
> by hand (showin it to friends and at the club) and doesn't
> have a trace of
> rust yet. It's just a 20g piece so I'm using it to see how
> sensitive it is.
>
> The bigger piece was stripped of the lacquer by CRC sealant stripper!
> It worked a lot faster than sanding it down. Then I gave it a
> quick polish
> and it too haven't had any problem.
>
> I use isopropylic alcohol before I cut meteorites as I have
> access to a
> rock saw with water based coolant. It goes into the pores and stops
> the water to go deep into it, it's so much easier to dry it
> afterwards.
>
> So far it's been working for me, but your mileage may vary.
>
> To form rust you need two things, oxygen and a media for the wet
> chemistry process to work in. If you could take away one part of
> the equation you could stop the rust forming.
> So either an inert atmosphere (nitrogen, carbon dioxide, neon... ),
> vacuum or absence of water will protect a specimen.
>
> The problem is to remove the water if there is any iron chloride
> salts present. That will work as a dessicator, drawing the humidity
> from the air and creating a perfect environment for rusting.
> The chloride irons also add to the process as a catalyst.
> My next step is to try to treat a piece of Brahin electrolytically
> to draw out the chloride. I'll come back later to report how it went.
>
> I do also belive in the preservation of Brahin is possible with
> the right treatment. I'm not giving up on this yet.
>
> Now I'm off to a mineral fair i Kopparberg. No, no Ensisheim for
> me, it's too far away.
>
> /G?ran
>
> Jim Strope wrote:
>
> > I agree with Matteo. You get what you pay for. Esquel, Imilac,
> > Albin, Glorietta, and a few others are investment quality
> pallasites.
> >
> > Brahin, Brenham and Admire have always had a bad reputation
> in general
> > although there are some speicmens that have lasted for
> years with no
> > traces of rust. I do believe that Brahin CAN survive with
> the proper
> > cutting and preparation, however.
> >
> > Jim Strope
> > 421 Fourth Street
> > Glen Dale, WV 26038
> >
> > http://www.catchafallingstar.com
> >
> >
>
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Received on Fri 17 Jun 2005 07:49:15 AM PDT