Corrosion

Neil Mahrer <neil.mahrer [at] jerseyheritagetrust__org> writes

>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?

Rather than go a chemical route, consider using an ultrasonic dental
descaler (also sold by some conservation suppliers without the
addition of water-spray or abrasive).  These can be used at low
power settings to remove very thin layers of material, with minimal
disruption to the substrate.

Howard Wellman
410-586-8577


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                  Conservation DistList Instance 18:42
                  Distributed: Friday, March 11, 2005
                       Message Id: cdl-18-42-007
                                  ***