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Re: Removing Rust




The real problem with rusting in meteorites is chlorine.  Rinsing the
meteorite with water, (tap water) should never be done if any
of these treatments is used.  For some reason, meteorite irons have
an affinity for chlorine, and it is chlorine that is the main cause
of rusting.

Often it comes to the surface of cut or wire brushed irons as little
dark brown or green blebs of fluid.

What this is is FeCl2, FeCl3, or even NiCl2, or NiCl3 (in much smaller
amounts)  

Ferric and Ferrous Chloride (FeCl2 & FeCl3) are hydroscopic substances,
that is they have an affinity for moisture jsut as a dessicant does.

Then once the water is present and these are in solution, the Chlorine
is free to bond to other iron atoms attacking it so that it will combine
with oxygen, producing iron oxide.  Once a thick coat of rust develops,
then the "bleeding" stops and the meteorite becomes more or less stable.

Some though, will continue to rust till they actually fall appart.

At one time the iron and nickel chlorides in meteorites were described as
"Lawrenceite" after the minerologist that first identified it.  It was
thought at the the the time that they were present in the meteorite before
it fell to earth, but it was later found that it was a substance that 
formed in the meteorite from reactions between terrestrial groundwater
and salts.


The trick to stop this rusting is to get rid of the chlorine.  Fortunately,
a good long soak in alcohol will dissolve iron-nickel chlorides, but I have
found a much better way.

Soak the affected specimen in a strong solultion of distilled water 50%;
iropropyl 30%, and sodium hydroxide 20%.  The percentages are by weight.

When mixing the sodium hydroxide crystals in this solution be very carful
as it gets hot.  Also it is caustic, and if gets on the skin will burn
just as badly as if it were an acid.

Use stainless steel containers.

Put the meteorite in the solution and let it soak for a few days to a 
week.  If the solution gets tainted so that it looks rusty then you
might want to replace the solution sooner than a week.  Pour out
the solution, and clean the surface of you meteorite.  This solution is
strong enough to strip most irons of their varnish coatings, but I
recommend that it is done beforehand.  You will notice after this first
soak that there are big blobs of gelatinous rust on the iron surface.
Some of these will be green but most will be dark brown.  This is
Fe0H and NiOH, both are like jelly in water but when exposed to air
expell their hydrogen and become solid iron an nickle oxides.

The chlorine that caused the rusting is now in the solution as NaCl,
(salt) having exchanged places with the iron atoms in the meteorite
for the Na (sodium) in the caustic solution.  Chlorine has a greater
attraction for sodium than iron, so that is why this solution works
better than just keepin air and moisture away from the meteorite.

Get rid of the chlorine, and you get rid of the problem.

I stumbled upon this process over 20 years ago, and have used it with
great success to treat some of the most stubborn rusting metorites in
my collection, including Brenham and more recently Lamont, which is
a messosiderite.  Lamont is a very unusual olivine rich meteorite,
maybe a link beteen the Lodranites and the mesosiderites, but unfortunately
it is a prolific ruster.

Soaking my 900 gram endpiece six times over six weeks has seemed to
cure it, as it is now on my shelf with no varnish coatiing and not
a speck of rust on its cut surface.

With pallasites, the crystals tend to pop out.  But if you are veryt,
very patient, andd like puzzles, you can clean the places where they
were, then re-insert them with super-glue.  Then after everyting is
together re-finish the surface so that it looks good as new.

Iron meteorite will, however have to be re-polished, and etched.

And be sure to use only distilled water so as not to re-infect your
meteorite with chlorine which is the primary cause of the progressive
rusting of our specimens in the first place.

This solution can also be used in electrolosis-- a much more agressive
method of removing chlorine from iron.  

This is done for the presrvation of iron artifacts that are recovered
from shipwrecks.  

It is more involved and it does work.




>
>I came across an article in a local newspaper titled 'Removing All Traces
>Of Rust', and here are some excerpts.  The article came from the Home & 
>Garden section concerning the removal of rust from household items, but 
>some of this info could apply to meteorites.  Note that I have not tried 
>any of the products mentioned in the article, so I don't know how effective
>they are in removing rust from meteorites.
>
>    Besides being unsightly, rust weakens the metal it attacks and
>    can create hazardous situations.  A child's swing set that is
>    weakened by rust, or a rusty propane tank that springs a leak,
>    are examples of hazardous rust.  Rust, which is actually iron
>    oxide, develops when iron and steel come in contact with air
>    and moisture.
>
>    Paint, which prevents air and moisture from reaching metal, is the 
>    usual preventive treatment for rust, but painting sometimes leaves
>    small openings that allow rust to get started.  Paint can also
>    flake and peel, which exposes the bare metal and leads to more
>    rusting.
>
>I never considered painting as a rust preventative measure,
>but it is generally out of the question anyway for meteorites.
>
>    One way to clean small objects, such as rusted small tools or
>    hinges, is to use a rust remover such as Naval Jelly, made by
>    Loctite (800-562-8483) and sold at many hardware stores and home
>    centers.  These removers, which dissolve rust, are expensive and
>    contain strong chemicals, however, and generally should be
>    avoided for large surfaces.  But rust removers are excellent
>    for cleaning smaller objects that won't be painted.  Rust removers
>    can also be used to remove rust stains from masonry such as
>    concrete, bricks and tiles.
>
>    To use a rust remover on metal, brush or scrape off loose rust
>    and apply a heavy coat of the remover with and old brush.
>    Let the remover soak for the time indicated on the label, then scrub
>    the metal with coarse steel wool dipped in rust remover.
>
>    Several applications of remover and extra soaking time might be
>    needed for badly rusted objects.  Finally, thoroughly rinse the
>    object with water to remove all traces of the remover.
>
>I have to jump in on this statement.  I though the purpose was
>to remove rust, but the rust remover requires rinsing in water??  
>It goes without saying that a thorough drying is needed after the water rinse,
>and in the case of meteorites, probably an alcohol bath to ensure all
>of the water is out of the meteorite.   
> 
>     Rust converters are another way to help stop the spread of
>     rust or prepare it for painting.  Coverters, such as Rust
>     Reformer by Rust-Oleum (800-323-3584) and Loctite's Extend
>     are a relatively new type of chemical treatment that does not
>     remove rust, but converts it into an inert substance.  Loose
>     rust is brushed or scraped off, then the liquid converter is
>     applied with a brush or pad.
>
>Ron Baalke
>
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