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Subject: Tannic acid and iron

Tannic acid and iron

From: George Bailey <george.bailey>
Date: Wednesday, May 2, 2001
Deborah Wallsmith <deborah_wallsmith [at] mail__dnr__state__ga__us> writes

>...  Does anyone know what the
>consequences might be of using tannic acid on iron that may still
>contain salts?

The application of tannic acid is not a recognised treatment for
salt contaminated iron. I would expect that any salt contaminated
iron would continue to corrode, despite that application of tannic
acid. The tannic acid may slow the process down, but I'm not sure on

However, since you stated that the artifacts have been soaking in
fresh water for 15 years, you can reasonably expect that many of the
chloride salts have been leached out, so they may not be as big a
problem as they would normally be. If the artifacts can't be
subjected to electrolytic reduction, then I'd first soak them in
acetone. This will help to dewater the artifacts, thereby removing
one of the essential ingredients for corrosion. Additionally, some
of the iron/chloride compounds are soluble in acetone, so you will
be removing more salt. After that, you might try the tannic acid,
followed by a coating of wax to act as a barrier to oxygen and
moisture. Hopefully, this will reduce the likelihood of future
corrosion. Best of luck,

George Bailey
Object Conservator
Australian War Memorial

                  Conservation DistList Instance 14:59
                    Distributed: Friday, May 4, 2001
                       Message Id: cdl-14-59-002
Received on Wednesday, 2 May, 2001

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