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Re: Electrolytic Cleaning of rust

Hello Jim and list,

A fabulous web resource which I would recommend is:

http://128.174.5.51/denix/Public/ES-Programs/Conservation/Underwater/archaeo
logy.html

Basic Methods of Conserving Underwater Archaeological Material Culture

Donny L. Hamilton

Nautical Archaeology Program,
Department of Anthropology,
Texas A&M University
Spring 1997

This document describes in considerable detail the chemistry of the
oxidation reactions which cause iron to corrode, as well as equipment and
procedures used to clean, restore, and stabilize iron artifacts. There are
also many references to the literature for those who want even more detail
on some aspect.

This is a bulky document; be warned that it may take several minutes to
load into your browser, and is more than 50 pages if you print out a hard
copy.

Although it is primarily aimed at conservation of artifacts recovered from
the marine environment -- the word "meteorite" is nowhere to be found -- a
lot of information useful to the meteorite collector can be obtained. For
example, the author has a lot to say about the chloride problem: the role
of chlorides in oxidation reactions, how to purge artifacts of their
chloride content, and the consequences of not succeeding in doing so.

There is a very detailed discussion of electrolytic (galvanic) cleaning.
The electrolyte of choice is in fact sodium carbonate, a.k.a. washing soda,
although sodium hydroxide (lye) was also commonly used in the past. Sodium
carbonate has the advantage of being safer to work with, but may not be the
best choice for treating artifacts which are heavily contaminated with
chlorides. Also of interest is a "low tech" galvanic cleaning process,
applicable to lightly corroded artifacts, which involves nothing more than
wrapping them in aluminum foil and immersing them in a sodium carbonate
solution.

There are many variants of equipment and techniques described, and no
single approach is best for all situations. The details are important:
container material, concentrations of solutions, strength of current,
temperature, etc. It would be best to read all of this material once before
starting in with your own first attempt.

DISCLAIMER: I have never tried electrolytic cleaning myself. There are
important differences between iron meteorites and Spanish cannons -- the
presence of sulphide and phosphide inclusion minerals is one which comes to
mind. Electrolytic cleaning may have unexpected and undesirable results. It
would be prudent to "start small" and be emotionally prepared for initial
disasters. I would be delighted to hear from someone who has some hands-on
experience with this technique.

Best wishes from gorgeous summery Amsterdam,

Piper


At 16:58 18-06-99 -0700, you wrote:
>
>I found this on a list related to restoring antique clockwork.
>
>There is a technique for removing rust by electrolysis that apparently
>does not alter metal (except for brass).
>
>The method uses washing soda (I believe that sodium carbonate) in warm water
>with an iron positive plate and the negative attached to the object.
>
>Has anyone heard about this or tried this on iron meteorites?
>
>I imagine the reaction is 
>
>    Fe02 + NaCO3 + energy -> FeCOn + O2 + NaOH
>
>but my high school chemistry is pretty rusty (ouch!).
>
>
>See these:
>http://www.bhi.co.uk/hints/rust.htm
>http://www.mcs.net/~brendler/oldtools/handsaws/handsaws.htm
>http://www.foxberry.net/dondon/rustfaq.html
>http://www.oldengine.org/members/rotigel/12herc/gene.htm
>
>--
>Jim Hurley  Freelance graphics artist
>Web page design; graphics; multimedia
>  <URL: http://www.arachnaut.org/ >
>
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