Corroding glass,corroding metals: Survey of joint metal/glass corrosion products on historic objects

Abstract

Corroding glass forms alkali(ne) surface films, which may lead to special metal corrosion products in the contact zone, for example different sodium copper carbonates or basic sodium lead carbonate. Sodium copper formate acetate was found on objects exposed to long term emissions from wood. A higher pH value may also lead to basic compounds, which normally do not form, e.g. the newly characterised Cu₂(OH)₃ HCOO. The alkaline films also create a reactive environment for the formation of formates from formaldehyde (e.g. emitted from glues) due to the Cannizzaro reaction or possibly from the neglected pollutant carbon monoxide. Further products containing, for example, potassium or sulphate may be expected.