ASSESSING INDOOR LEAD CORROSION USING RAMAN SPECTROSCOPY DURING ELECTROCHEMICAL REDUCTION

Even though kept in cultural institutions, artefacts can besubjected to accelerated deterioration due to high concentrationof pollutants in closed spaces. Potentially harmfulconditions have been evaluated by electrochemical reductionof corrosion products formed on metallic couponswhich have been exposed in selected places. In the case ofsilver coupons, this technique allowed chemical identificationof the tarnish layer (sulphides and chlorides), as wellas determination of the amount in which they are presenton individual coupons. Extension of this approach to leadraises some difficulty as identification of the reductionpeaks is more complex. In this work we combined electrochemicalreduction of corrosion products with in-situRaman spectroscopy to unambiguously correlate the reductionpeaks with the compounds present on the surface ofcoupons previously exposed in different French institutions.Raman analysis carried out prior to the electrochemicalreduction in a sodium sesquicarbonate solutionrevealed that the corrosion layer contains lead oxides,hydroxycarbonates and carbonates and in some cases formatesand acetates.