Corrosion

I am seeking advice about how best to selectively remove iron
corrosion products without affecting an underlying copper patina.
The object in question is an 18th Century copper alloy sundial with
a stable dark brown/green patina.  At some point recently a paint
tin or similar has been left standing on the sundial and has left a
thin orange stain where it has touched.  The copper patina looks too
thin to attempt localised cleaning with any kind of metal polish so
I was wondering if di-sodium EDTA or a similar chemical could
selectively removed this rust staining?


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                  Conservation DistList Instance 18:40
                 Distributed: Monday, February 28, 2005
                       Message Id: cdl-18-40-027
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