[meteorite-list] Re: rust, cleaning, and silicone

From: Steve Schoner <steve_schoner_at_meteoritecentral.com>
Date: Thu Apr 22 10:30:01 2004
Message-ID: <20030928155220.67384.qmail_at_web12701.mail.yahoo.com>

--- Stephen McMann <stephen_mcmann_at_hotmail.com> wrote:

---------------------------------

Dear List,

A quick question regarding rust. I have been mulling
over a simple strategy for the long term care of my
SAs (and other meteorites). Right now it seems that a
good strategy is to give the SAs an alcohol and NaOH
treatment to dispose of the Cl- from fingerprints
etc., and otherwise keep them with VCIs and dessicant.

A possible complication is that several of my SAs were
once wiped with a silicone gun cloth (by me). However,
for the alcohol and NaOH treatment to be most
effective I assume that the silicone coating should
go. What is a good method for removing such a
coating? Will the alcohol and NaOH remove it? If
anyone has some thoughts about this, I would be
interested in them. Hopefully I am asking for
information that is not just waiting in the archives.

Sincerely,

Stephen McMann
------




NaOH with alcohol should remove it.

Mix alcohol 70% with 40% or more of distilled water to
avoid a layer of brine. If such a lay forms keep
adding just enough water to eliminate that layer then
the solution will be ready for soaking specimens.

Currently, I am soaking several meteorites. A big 158
lb Campo for Darryl Pitt, a small slice of Brenham, an
end piece of Doronio, and a slice of Brahin for
Matteo.

All of these had advanced rusting problems. The large
Campo has been soaking for 6 months in 25 quarts of
solution, it should soon be ready for removal and
drying in another month or so. If the flaking has
stopped the specimen will be cured.

The smaller pieces were treated with a coating, and
the rust was quite bad. In fact two of the samples
had fallen appart, and part of my process is to put
them back together. Once the rusting is cured, after
soaking these pieces for a month, reconstruction can
be done with some patience. (Currently, at this
point in my life I have lots of time).

I will post the results.

But again, yes, the NaOH will get through any coating
that is on the specimen. In fact it will even soften
a thick epoxy coating softening it like rubber which
peels off.

I have treated SA's before, and the fusion crust is
not harmed other than the specific areas that are
rusting with chlorides. These spots turn into dark
brown oxides. But the oxide is very thin and
superficial and with a tooth brush comes off to reveal
the original surface underneath.

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

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Received on Sun 28 Sep 2003 11:52:20 AM PDT