A multi-analytical protocol combining EDXRF, SEM+EDS, μXRD and Monte Carlo simulations applied to analyse non-destructively portuguese corroded copper coins

Performing quantitative analyses on archaeological and cultural heritage metallic artefacts is challenging due to their complex multi-layered internal structure. “Layers” may include a) Original metal and/or alloy substrate (gold, silver, bronze etc.) b) Surface patinas enriched in corrosion products sulphides, oxides and/or chlorides compounds c) Protective treatments applied in past conservation interventions d) Soil derived incrustations from archaeological burial environment. To obtain compositional data on the metal substrate, usually these layers have to be removed but this not always possible due to the inherent fragility of the corroded artefacts as it is the case in particular with copper objects such as coins. The setting up of a non-destructive protocol is therefore important. In this study, a protocol combining SEM-EDS, μXRD, EDXRF and Monte Carlo simulations has been tested on a series of Portuguese coins from the 12th to the 19th centuries found at Largo das Olárias and Travessa do Jordão in Lisbon. 1. Analyze non-destructively the corrosion patterns and patinas developed on the surface Portuguese Copper coins from a Lisbon archaeological site (Largo das Olarias) SEM+EDS, μXRD and portable EDXRF 2. Apply the mineralogical and chemical data obtained during the analytical sessions to run Monte Carlo simulations of EDXRF spectra 3. Assess the feasibility of the combined non-destructive protocol in obtaining a reliable quantitative estimation of the metal substrate composition without the need to remove the surface corrosion patinas; RESUMO: Realizar análises quantitativas em artefactos metálicos arqueológicos de património cultural é um desafio devido à sua estrutura interna com múltiplas camadas. Essas ‘’Camadas’’ podem incluir: a) Substrato original de metal e / ou liga (ouro, prata, bronze etc.) b) Patinas de superfície enriquecidas em produtos de corrosão compostos de sulfetos, óxidos e / ou cloretos c) Tratamentos de protecção aplicados em intervenções de conservação passadas d) Incrustações ...