Assessing indoor lead corrosion using Raman spectroscopy during electrochemical reduction
Résumé
Even though kept in cultural institutions, artefacts can be
subjected to accelerated deterioration due to high concentration of pollutants in closed spaces. Potentially harmful
conditions have been evaluated by electrochemical reduction of corrosion products formed on metallic coupons
which have been exposed in selected places. In the case of
silver coupons, this technique allowed chemical identification of the tarnish layer (sulphides and chlorides), as well
as determination of the amount in which they are present
on individual coupons. Extension of this approach to lead
raises some difficulty as identification of the reduction
peaks is more complex. In this work we combined electrochemical reduction of corrosion products with in-situ
Raman spectroscopy to unambiguously correlate the reduction peaks with the compounds present on the surface of
coupons previously exposed in different French institutions. Raman analysis carried out prior to the electrochemical reduction in a sodium sesquicarbonate solution
revealed that the corrosion layer contains lead oxides,
hydroxycarbonates and carbonates and in some cases formates and acetates.