Deterioration of submarine metal objects

In reply to Vera Espinola's query, A number of years ago, I worked
on a batch of marine iron artifacts excavated from San Francisco Bay
(one of the ships that was abandoned and sunk during the 1849 gold
rush).  In the process of reducing chloride content by soaks in
deionized H2O, I was aided by a very helpful "auto-reduction"
phenomenon that mimicked electrolytic reduction but without an
electrolyte (other than H2O) or any use of electrical power.  The
most likely source of this help was iron-reducing or
sulphur-reducing bacteria which is present in the essentially
anaerobic saline muck in which the iron was found.

The bacterial action helped remove a great deal of corrosion crust
from the artifacts and undoubtedly aided removal of chlorides by
providing diffusion paths through the corrosion layer.  The
artifacts were subsequently treated with a corrosion inhibitor and
as far as I know, have been stable since.

I would not doubt the presence and activity of iron-reducing
bacteria on the Titanic.

Geoffrey I. Brown
Curator of Conservation
Kelsey Museum
University of Michigan
Ann Arbor, MI 48109-1390, U.S.A.
734-647-0439
Fax: 734-763-8976

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                  Conservation DistList Instance 11:54
               Distributed: Wednesday, December 17, 1997
                       Message Id: cdl-11-54-006
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