Assessing Indoor Lead Corrosion Using Raman Spectroscopy during Electrochemical Reduction

key words: Lead corrosion, Raman spectroscopy, oxide reduction, organic acids, electrochemistry 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.