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. ...

One of the cheapest ways of dealing with ferric corrosion and
stopping it spreading is application of tannins.  Only there is side
effect of using tannins.  They won't give you brown patina.  Tannins
will turn ferric oxide and chloride into bluish or greenish black
compound depending on what tannin will be used.  You can find a
variety of sources for tannins from one of the products on a list of
your laboratory or chemical suppliers down to plants with its high
content (such like an ordinary black tea).

We recently had to use for exhibition set of school benches (oak on
metal skeleton) from beginning of the 20th century.  Metal was
painted black but with large areas of brown corrosion and paint
flaked off which had to be removed in order to be used by children.
Strong (10 teabags per cup) tea was brewed and with soft metal wool
applied by gentle rubbing (If layer of rust has to be preserved
non-abrasive application like brushing can be used).  Surplus of
corrosion products was removed and at the same time areas where tea
had no/or slower effect due to thicker layer of rust became apparent
so needed additional treatment.  Warm tea will accelerate chemical
reaction.  Tea/tannin was applied three or four times to achieve
right effect.  Afterwards metal parts were coated with
microcrystalline wax.

Hope it might be of some help (as a suggestion of course),

Peter Juga
Conservator
Seven Stories
United Kingdom


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                  Conservation DistList Instance 23:26
                Distributed: Wednesday, January 20, 2010
                       Message Id: cdl-23-26-003
                                  ***