Surface studies of environmental reactive species during exhibition or storage of ancient Ag-based artefacts † F. Faraldi, a * E. Angelini, a A. Mezzi, b C. Riccucci, b T. de Caro b and G. Di Carlo b The role played by environmental species affecting the long-term stability of archaeological Ag-based artefacts during museum exhibition or storage has been studied by means of the combined use of selected area X-ray photoelectron spectroscopy, X-ray dif- fraction, optical microscopy and scanning electron microscopy + energy dispersive spectrometry. The presence of fine particulate and of aggressive compounds in the museum atmospheres has been investigated by means of an innovative testing methodology based on Ag-based reference alloys. The procedure has been applied to different areas of some museums in the Mediterranean Basin in order to consider representative environmental conditions of storage and exhibition of Ag-based artefacts. The case studies of the National Roman Museum in Rome, Italy and of the Egyptian Museum of Cairo, Egypt will be illustrated. Furthermore, the study has been performed as a function of the alloy chemical composition and of the position of the reference specimens. The results of the superficial, micro-chemical and morphological characterisations of the reference alloys are related to degradation parameters of ancient silver artefacts, as the presence of sulfur dioxide and chloride ions. The chosen methodology can be recommended to investigate the environmental key factors to consider for a safe storage or exhibition of archaeological silver artefacts, ensuring them a long stable life from a chemical–physical point of view. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: Ag-based artefacts; Sulphides; Chlorides; SA-XPS Introduction Monitoring of the aggressivity of the environment, both by evaluating the presence of aggressive chemical compounds and the amount of particulate in the exhibition rooms, in showcases and store boxes, where highly precious artefacts are exhibited or stored, is very important for the conservation of ancient metallic artefacts. [1–6] The diagnosis and the potential damage evaluation can be performed by evidencing the presence of some critical elements such as Cl and S or other dangerous chemical compounds on the artefact surface. On the basis of the experimental findings, tailored preventive conservation and maintenance strategies can be developed. [1–6] The evaluation of the aggressivity of an environment, where the artefacts have to be exhibited or stored, may be performed in advance by studying the interactions between the environ- ment and reference alloys properly designed and produced. The chemical composition of reference silver-based alloys was selected on the basis of analytical information obtained by the study of silver archaeological artefacts, of literature results and X-ray fluorescence (XRF), in situ measurements carried out in the Egyptian Museum. [7–10] This approach allows to evidence the presence of atmospheric corrosive compounds which inter- act with the alloys, giving rise to the formation of specific corro- sion products during the exposure to indoor atmosphere. These reference materials can be also used to test, in advance, the environment of exhibition rooms and showcases where aggres- sive agents could be potentially present. [1–3] With these considerations in mind, in the frame of the PROMET project, the effect of the environment on the artefacts has been studied by means of the combined use of selected area X-ray photoelectron spectroscopy (SA-XPS), X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy + energy dispersive spectrometry (SEM + EDS). In particular, the particulate and the reactive compounds potentially present in the museum atmospheres (exhibition rooms, storage rooms, showcases, open atmosphere) have been investigated by means of an innovative testing methodology based on Ag-based refer- ence alloys, whose chemical composition, metallurgical features and micro-chemical structure are similar to the ones of the ancient alloys; in particular, two alloys characterised by two different copper amounts have been produced being representa- tive of largely used classes of ancient Ag-based alloys. This procedure has been applied in different museums of the Mediterranean Basin in order to have a number of locations representative of the environments where the archaeological Ag-based artefacts are exposed or stored. Hereafter, the results achieved from the study of the reference Ag-based alloys exposed in two representative museums of the Mediterranean Basin (National Roman Museum, Rome, Italy and Egyptian Museum, Cairo, Egypt) are presented and discussed. * Correspondence to: F. Faraldi, Department of Applied Science and Technology, Polytechnic of Turin, Corso Duca degli Abruzzi 24, 10129 Turin, Italy. E-mail: federica.faraldi@ismn.cnr.it † Paper published as part of the ECASIA 2013 special issue. a Department of Applied Science and Technology, Polytechnic of Turin, Corso Duca degli Abruzzi 24, 10129 Turin, Italy b Institute for the Study of Nano-structured Materials—CNR, 00016 Monterotondo Scalo, Rome, Italy Surf. Interface Anal. 2014, 46, 796–800 Copyright © 2014 John Wiley & Sons, Ltd. ECASIA special issue paper Received: 26 September 2013 Revised: 10 December 2013 Accepted: 7 February 2014 Published online in Wiley Online Library: 12 March 2014 (wileyonlinelibrary.com) DOI 10.1002/sia.5445 796