Deterioration of submarine metal objects

Vera B. Espinola <icona<-a t->gte< . >net> writes

>A biologist working with the R.M.S. Titanic, Inc. has theorized that
>"rusticles" (visually appearing as stalactite-like formations of
>ferric oxide and ?? adhering to the underwater wreck of the
>Titanic) are colonies of an unidentified bacteria that are eating
>away at the iron content of the steel of the ship, causing it to
>disintegrate. As a conservator, I am amazed at this theory and would
>welcome comments from archeological metals conservators and
>scientists--especially those who either have worked with submarine
>metal objects or are conducting research on the same.

Corrosion of iron by bacteria is a known phenomenon. The bacteria
are generally of the genus "Thiobacillus". These are anaerobic
beasties that survive by oxidating sulphur, sulphide and some other
sulphur compounds. In doing so they produce sulphuric acid, which
then corrodes iron. A wreck like the Titanic would be an ideal
breeding ground for the bacteria--lots of sulphur compounds from
the coal bunkers, vulcanised rubber, etc, little water movement, low
O2 concentration, and no natural light. For more information consult
"Corrosion Volume 1: Metal/Environmental Reactions" by Shreir (ed),
published by Butterworths.

George Bailey
Objects Conservator
Australian War Memorial
Treloar Centre for Conservation
4 Callan St, Mitchell, A.C.T. 2911
Australia
+61 6 241 6122
Fax: +61 6 241 7998

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                  Conservation DistList Instance 11:54
               Distributed: Wednesday, December 17, 1997
                       Message Id: cdl-11-54-008
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