Metal alloys, matrix inclusions and manufacturing techniques of Moinhos de Golas collection (North Portugal): a study by micro-EDXRF, SEM–EDS, optical microscopy and X-ray radiography

"Article:820"A collection of 35 metallic artefacts comprising various typologies, some of which can be attributed to the Bronze Age and others to later periods, were studied to provide detailed information on elemental composition, manufacturing techniques and preservation state. Elemental analysis by micro-EDXRF and SEM–EDS was performed to investigate the use of different alloys and to study the presence of microstructural heterogeneities, as inclusions. X-ray radiography, optical microscopy and SEM–EDS were used to investigate manufacturing techniques and degradation features. Results showed that most of the artefacts were produced in a binary bronze alloy (Cu–Sn) with 10–15 wt% Sn and a low concentration of impurities. Other artefacts were produced in copper or in brass, the latest with varying contents of Zn, Sn and Pb. A variety of inclusions in the metal matrices were also found, some related to specific types of alloys, as (Cu–Ni)S2 in coppers, or ZnS in brasses. Microstructural observations revealed that the majority of the artefacts were subjected to cycles of thermomechanical processing after casting, being evident that among some artefacts different parts were subjected to distinct treatments. The radiographic images revealed structural heterogeneities related to local corrosion processes and fissures that seem to have developed in wear-tension zones, as in the handle of some daggers. Radiographic images were also useful to detect the use of different materials in one particular brass artefact, revealing the presence of a possible Cu–Sn solder.This work was funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT— Fundação para a Ciência e a Tecnologia under the project UID/CTM/ 50025/2013 to CENIMAT/I3N. C2 TN/IST authors gratefully acknowledge the FCT support through the UID/Multi/04349/2013 project. EF acknowledges FCT for the grant SFRH/BPD/97360/2013. JF acknowledge FCT for the grant SFRH/BD/65143/2009. Part of this project has been done in the framework of the FCT project ENARDAS (PTDC/HISARQ/112983/2009).info:eu-repo/semantics/publishedVersio

LA CORROSIONE ATMOSFERICA DEI MONUMENTI IN BRONZO: PROVE DI INVECCHIAMENTO ARTIFICIALE

I monumenti in bronzo esposti all’aperto risentono di diverse tipologie di degrado, in conseguenza delle diversecondizioni di esposizione all’ambiente e, in particolare, alla pioggia.Allo scopo di studiare la correlazione causa-effetto tra l’evoluzione della corrosione di un bronzo e la suadifferente esposizione alla pioggia (pioggia stagnante o pioggia lisciviante), è stato intrapreso un lavoro di ricercamultidisciplinare. Nel presente lavoro vengono quindi riportati i risultati delle prove eseguite sul bronzo quaternarioG85, largamente impiegato per fusioni artistiche. La soluzione aggressiva impiegata è stata formulata sulla base dellecaratteristiche di piogge reali raccolte nell’area urbana di Bologna. La condizione di stagnazione è stata riprodottamediante un dispositivo wet&dry specificamente progettato e realizzato, in cui il bronzo viene ciclicamente immersonella pioggia sintetica, che viene periodicamente analizzata per valutare l’evoluzione del pH e della concentrazionedi metalli dissolti. Parallelamente, anche i materiali esposti vengono caratterizzati mediante misure gravimetriche,VPSEM+EDS+micro-Raman e XRD. La condizione di pioggia battente (run-off) viene invece simulata medianteun apposito dispositivo di dropping, che intende riprodurre, in condizioni controllate, l’azione della pioggia suuna superficie inclinata a piacere. Anche in questo caso sia le superfici esposte che la soluzione lisciviante vengonoanalizzate parallelamente nel corso dell’esposizione.L’analisi dei dati ottenuti ha permesso la formulazione di modelli interpretativi per i processi di corrosione delbronzo quaternario; inoltre, il confronto con casi reali di corrosione di monumenti bronzei ha consentito di stimarel’affidabilità dei modelli proposti e la loro efficacia a fini diagnostici e conservativi

Ancient coins: cluster analysis applied to find a correlation between corrosion process and burial soil characteristics

Although it is well known that any material degrades faster when exposed to an aggressive environment as well as that "aggressive" cannot be univocally defined as depending also on the chemical-physical characteristics of material, few researches on the identification of the most significant parameters influencing the corrosion of metallic object are available

FIB-FESEM and EMPA results on Antoninianus silver coins for manufacturing and corrosion processes

[EN] A set of ancient Antoninianus silver coins, dating back between 249 and 274¿A.D. and minted in Rome, Galliae, Orient and Ticinum, have been characterized. We use, for the first time, a combination of nano-invasive (focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), voltammetry of microparticles (VIMP)) and destructive techniques (scanning electron microscopy (SEM-EDX) and electron microprobe analysis (EMPA)) along with non-invasive, i.e., micro-Raman spectroscopy. The results revealed that, contrary to the extended belief, a complex Ag-Cu-Pb-Sn alloy was used. The use of alloys was common in the flourishing years of the Roman Empire. In the prosperous periods, Romans produced Ag-Cu alloys with relatively high silver content for the manufacture of both the external layers and inner nucleus of coins. This study also revealed that, although surface silvering processes were applied in different periods of crisis under the reign of Antoninii, even during crisis, Romans produced Antoninianus of high quality. Moreover, a first attempt to improve the silvering procedure using Hg-Ag amalgam has been identified.Financial support was provided by Sapienza University of Rome (Ateneo funding, 2014 15) and Spanish projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P, which are supported with Ministerio de Economía, Industria y Competitividad (MINECO) and Fondo Europeo de Desarrollo Regional (ERDF) funds, as well as project CTQ2017-85317-C2-1-P supported with funds from, MINECO, ERDF and Agencia Estatal de Investigación (AEI). PhD grants of the Department of Earth Sciences, Sapienza University of Rome, are gratefully acknowledgedDomenech Carbo, MT.; Di Turo, F.; Montoya, N.; Catalli, F.; Doménech Carbó, A.; De Vito, C. (2018). 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