Removing rust from farm tools

Suzanne Singleton <msingleton [at] fmarion__edu> writes

>... I have been asked to assist in a metal
>conservation problem.  There is a collection of farm tools
>associated with two circa 1836 slave cabins on our campus. ...

If there are thick deposits of corrosion material on the surface,
some form of mechanical cleaning may be necessary before applying
the tannic acid.  We did preliminary cleaning of farm tools at
Jefferson Patterson Park and Museum with a walnut shell grit blaster
at 60psi to remove superficial corrosion deposits, leaving enough
oxide patina to react with the tannic acid.

You should note though that tannic acid treatment will not inhibit
future corrosion if the metal has an inherent problem, eg
salt-driven corrosion.  Storage in a controlled environment after
treatment is recommended.  Tannic acid treatments are also
water-soluble, so the treated objects cannot be left out in the
weather.  The respondents suggestion of a microcrystalline coating
over the TA treatment is a good one, though solvent-resin coatings
like Paraloid B72 are also effective, and can be removed more easily
if the objects need to be retreated in the future.

Howard Wellman
Howard Wellman Conservation LLC
PO Box 938
Owings, MD 20736
Office 410-286-3570
Mobile 410-474-1226


                                  ***
                  Conservation DistList Instance 23:27
                Distributed: Thursday, January 28, 2010
                       Message Id: cdl-23-27-001
                                  ***