The conservation of historical aluminium aircraft exposed to outdoor conditions requires protective systems combining corrosion mitigation, aesthetic compatibility and chemical stability. Within the PROCRAFT project two advanced coatings, namely, a bio-based cutin-derived polyurethane and a 3-mercaptopropyl trimethoxysilane (PropS-SH)-based system, were comparatively evaluated against the benchmark Paraloid B72 (PB72) on historic corroded and painted Duralumin substrates dating from World War II and the immediate post-war period. Coupons were subjected to an accelerated ageing protocol including simulated acid rain runoff, followed by thermo-hygrometric and UV cycling. Protective performance was assessed through a multi-analytical approach integrating electrochemical tests, colour analysis, SEM-EDS, ATR-FTIR, mu-Raman, and metal release quantification by MP-AES. On corroded substrates, both innovative coatings exhibited higher polarization resistance than PB72 and values two orders of magnitude greater than those of uncoated surfaces after ageing. PropS-SH provided inhibition efficiencies >= 95% in terms of Al release, while the cutin-based coating achieved inhibition efficiencies >85%, outperforming PB72 under the same conditions. On painted substrates (already intrinsically protective) PropS-SH produced up to a one-order-of-magnitude increase in polarization resistance compared to the original paint system, whereas PB72 provided only marginal improvements. Spectroscopic analysis after ageing revealed progressive siloxane network densification in PropS-SH and, in the cutin-based coating, continued crosslinking accompanied by UV-mitigating behaviour attributable to residual natural antioxidants. Overall, both coatings provided effective corrosion protection on painted and corroded substrates, with PropS-SH exhibiting superior performance in suppressing metal release and enhancing polarization resistance, while maintaining good aesthetic stability throughout the artificial ageing process.

Outdoor glass is subject to degradation due to environmental factors, which alter its physical and chemical properties depending on the exposure conditions. Studying glass weathering and the effectiveness and durability of conservation treatments is necessary for developing optimal conservation strategies for glass heritage objects. Here, an accelerated aging protocol based on actual environmental data is successfully employed to replicate weathering caused by rain runoff, temperature, humidity and UVA radiation in unsheltered conditions. Two types of silicate glass with traditional compositions were artificially aged to investigate the corrosion processes and produce representative weathered substrates for applying and aging protective treatments. The performance of two recently marketed Siox-5 sol–gel systems was compared with that of Paraloid B72. Glass specimens, as well as leaching rain solutions, were analyzed with different techniques, including SEM/EDS, FTIR-ATR, color measurements and MP-AES. The composition of the glass influences weathering patterns, which in turn affect coating adhesion and overall performance. Sol–gel coatings demonstrate good chemical stability and tend to adhere more effectively to degraded surfaces than to well-preserved ones. The coatings exhibit varying degrees of sensitivity to environmental factors, with one of the sol–gel systems generally performing better than the others under the considered exposure conditions.

The impact of particulate matter (PM) on the deterioration of outdoor cultural heritage is of increasing concern, given the recent trends in atmospheric emissions. This work presents a novel method for investigating the effects of PM on bronze corrosion by combining the collection of ambient PM directly on metal substrates and ageing under controlled laboratory conditions, with the development of a predictive model based on chemometrics. PM deposits of different mass and composition were collected and chemically characterised using Ionic Chromatography, Total Organic Carbon, and Atomic Absorption Spectroscopy. Accelerated ageing was then performed in a climatic chamber simulating daily and seasonal environmental conditions characteristic of Southern Europe. The morphology and distribution of the deposited PM, as well as surface changes after deposition and artificial ageing, were analysed using microscopic and spectroscopic techniques. The alloying metals contained in the patina formed during the corrosion process - either in the water soluble/poorly adherent or in the insoluble/adherent fractions - were also quantified. Based on the collected data and the analyses results, principal component analysis and partial least squares techniques were employed to infer the correlation between the concentration of nitrite, chloride, sulphate and nitrate in PM and bronze corrosion. Multivariate regression allowed the influence of the different ionic species to be estimated, highlighting the primary role of chloride and sulphate ions in determining higher mass loss, and to define a cross-validated model for predictive purposes. The novel method proposed here can improve the understanding and prediction of the role of PM in the corrosion of bronze, ultimately providing guidance for targeted interventions in the preservation of outdoor cultural heritage.

The development of Healthcare-Associated Infections (HAIs) represents an increasing threat to patient health. In this context, Pseudomonas aeruginosa is responsible for various HAIs, determining about 20% of the infections in hospitalized patients, which makes it one of the most effective pathogens due to its strong ability to form biofilms. Using Cu-based materials as foils on high-touch surfaces can help to prevent and mitigate P. aeruginosa contamination in biohazardous settings. However, the antibiofilm properties of Cu-based surfaces against P. aeruginosa may vary due to frequent touches combined with indoor environmental exposure. The main aim of this study is to investigate the impact of accelerated ageing, mimicking a high-touch frequency by cyclic exposure to artificial sweat solution as well as to temperature and relative humidity variations, on the efficacy of Cu-based thin foils against P. aeruginosa biofilms. Three Cu-based materials (rolled and annealed Phosphorous High-Conductivity (PHC) Cu, Cu15Zn brass, and Cu18Ni20Zn nickel silver) were evaluated. The ageing process enhanced the antibiofilm properties, due to an increment in Cu ion release: aged PHC Cu and Cu15Zn exhibited the highest Cu ion release and hence the highest biofilm inhibition (decrease in colony forming unit (CFU)) in comparison to their pristine counterpart, while aged Cu18Ni20Zn displayed the lowest biofilm formation reduction, despite showing the highest aesthetic and morphological stability. The Cu-based surface, which highlited the highest biofilm formation inhibition due to accelerated ageing, was Cu15Zn.

This work reports the study of metal fragments from Roman pipes excavated from the archaeological site of Pompeii and currently preserved in the deposits of the National Archaeological Museum of Naples (MANN). The Roman pipe, called the tibia, is a reed wind musical instrument similar to the Greek aulos. It can be made of wood, bone, and/or metal. Materials consisting of metal Cu-based alloys were excavated from archaeological burial environments. This research aims to identify the composition of the alloys, characterize the corrosion patinas, and identify any ancient surface treatments on the fragments. Non-invasive and micro-invasive techniques were used to achieve this aim, i.e., optical microscopy, Raman spectroscopy, attenuated total reflectance Fourier-transform infrared spectrophotometry, scanning electron microscopy, and energy dispersive spectrometry. This research contributes to a deeper understanding of the materials and manufacturing techniques used for these instruments, as well as the degradation processes occurring over the centuries.

The development of innovative solutions for the conservation and the protection of historic aircraft is a recent and important issue raised in the cultural heritage field and represents the goal of the PROCRAFT (Protection and Conservation of Heritage Aircraft) project. Assessing and documenting the constituent materials as well as their degradation state is necessary to determine and understand factors inducing aluminium alloy corrosion, in order to develop tailored conservation treatments and identify effective protective coatings. The first step of the project was the identification of the constituent materials of aircraft wrecks. Al-Cu-Mg alloys—Duralumin and Super Duralumin, with a higher content of Mg—were the most employed alloys for structural and non-structural parts. These materials undergo a wide range of alterations, amongst which pitting, exfoliation and galvanic corrosion. In the present work, results of the characterisation of wrecks from a North American Republic P-47D Thunderbolt, crashed in Italy in 1945, are reported and compared to wrecks from a French Breguet 765 Sahara n°504 64-PH, built in 1958. The constituent alloys resulted to be similar to the modern 2024 and 2017A alloy. In order to assess the representativeness of these modern alloys in simulating the corrosion behaviour of the historic ones, exfoliation susceptibility (ASTM G34) as well as non-destructive and destructive electrochemical tests in 0.1 M NaCl were carried out on both historic and modern alloys. These results contributed to the selection of representative substrates for the development of protective coatings as well as to the expansion of the dataset on composition and microstructure of historic Al alloys for aircraft.

The healthcare-associated infections (HAIs) and pandemics caused by multidrug-resistant (MDR) and new-generation pathogens threaten the whole world community. Cu and its alloys have been attracting widespread interest as anti-contamination materials due to the rapid inactivation of MDR-superbugs and viruses. Applying thin Cu-based foils on pre-existing surfaces in hygiene-sensitive areas represents a quick, simple, cost-effective self-sanitising practice. However, the influence of chemical composition and microstructure should be deeply investigated when evaluating the antimicrobial capability and durability of Cu-based materials. The effect of composition on micromechanical and antiviral properties was investigated by comparing Cu15Zn and Cu18Ni20Zn (foil thickness from 13 to 27 μm) with Phosphorous High-Conductivity (PHC) Cu. The influence of recrystallisation annealing of PHC Cu was also investigated. Microstructural characterisation was carried out by optical (OM) and scanning electron (FEG-SEM) microscopy, Energy-dispersive Spectroscopy (EDS) and Electron-Backscattered Diffraction (EBSD). The micromechanical behaviour was assessed by microhardness, microscale abrasion and scratch tests. Cu-based foils were exposed to SARS-CoV-2 for different time points in quasi-dry conditions (artificial sweat solution), evaluating their antiviral capability by quantitative Reverse-Transcriptase Polymerase Chain Reaction (qRT-PCR). Surface morphology, contact angle measurements and Cu release were measured. All Cu-based surfaces completely inactivated SARS-CoV-2 in 10 min: pure Cu was the best option regarding antiviral efficiency, while Cu15Zn showed the best trade-off between micromechanical and antiviral properties.

Historical-artistic heritage, when located outdoor, is heavily targeted by deterioration phenomena such as weathering and air pollution. This is especially true for terracotta artefacts, as the medium porosity which characterizes them makes their damaging easier. Nevertheless, there is limited academic research on conservation strategies with regards to coatings. Consequently, the restoration of the carbonate terracotta sculpture known as "Muro del vento" (Wind Wall) by Domenico Matteucci has become the starting point for an experimental investigation carried out in order to evaluate the effectiveness and durability - for outdoor terracotta artworks - of an array of protective coatings. In this paper, four commercial protective coatings, recommended both for natural and artificial stones, were evaluated: a vinylidenefluoride-hexafluoropropene copolymer at 3 % in acetone, an aqueous emulsion of alkylpolysiloxane, an aqueous dispersion of functionalized silica nanoparticles, and a nanostructured and functionalized silica gel in hydroalcoholic solution. Coated and uncoated representative calcium-rich terracotta specimens were subjected to two different accelerated ageing procedures: rain runoff test and climatic chamber exposure. Concurrently, a long-term outdoor exposure was set up. The characterization of the specimens and the evaluation of the coating's performances were carried out through color, contact angles, water absorption and mass variation measurements, 3D digital microscopy, scanning electron microscopy, X-Ray diffraction, Raman micro-Spectroscopy and atomic absorption spectroscopy in order to quantify calcium release in rain. Overall, the proposed accelerated ageing procedures proved to be successful for evaluating effectiveness and durability of protective treatments on ceramic materials. Silicon-based coatings, especially nanostructured and functionalized silica gel, followed by alkylpolysiloxane emulsion, have been shown to be the most suitable coatings for outdoor terracotta artefacts, while the fluorinated coating did not provide adequate protection as it was not able to limit water absorption under runoff conditions. (c) 2024 The Authors. Published by Elsevier Masson SAS on behalf of Consiglio Nazionale delle Ricerche (CNR). This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

This paper will address art glass conservation, focusing on the search for the best products and methods to be employed in glass vessels’ reconstruction, including case studies. In 2000, an archaeological site was found in Padua (Northern Italy) where the Santa Chiara in Cella Nova Monastery once stood (1325–1797), and thousands of Renaissance artefacts came to light. Thanks to a collaboration between the Soprintendenza Archeologia, Belle Arti e Paesaggio per l’Area Metropolitana di Venezia e le Province di Belluno, Padova e Treviso and the University of Bologna, a huge conservative project started. The conservative intervention on the precious glass vessels became the starting point of a research on the best products to be employed in their reconstruction. More than for other materials, an analytical approach is necessary while dealing with glass: commonly employed techniques need to be adapted to suit features of every object, and new ones must be examined. Furthermore, testing and comparing well known products to most recent ones or to ones developed for other purposes is essential. In this study, an acrylic resin and four epoxy resins were tested, the latter both pure and added with three different colouring agents. Accelerated ageing tests were run to find out the products most resistant to discolouration through time. The results were compared with practical application’s tests to select the best combination of products and techniques. Finally, the intervention on two glass vessels, coming from Santa Chiara Monastery, is presented briefly.

Duralumin-type alloys have been employed for structural and non-structural parts of aircraft since the early 1920s up to now. In the European project “PROtection and Conservation of Heritage AirCRAFT” (PROCRAFT), up to 34 aircraft wrecks from World War II from different nations (United States of America, United Kingdom, France, Germany, Italy) were identified. On most of them, the collection of numerous fragments was possible, thus constituting a large sampling group. A metallographic analysis was carried out, and elemental composition, microstructure and hardness were measured. This article focuses firstly on the elemental composition of this group of historical Al alloys. From these data, some fine characteristics specific to the manufacturing countries will be investigated through principal component analysis. Then, on a restricted group constituted of German alloys, we will discuss how some manufacturing parameters, such as micro-alloying and thermo-mechanical treatments, influence the mechanical properties of the assessed aircraft components. Other influencing parameters, linked to the archaeological nature of the parts, are considered and addressed based on a specific study of an alloy collected on a crashed JU88 aircraft originating from the German company Junkers.

Outdoor Cultural Heritage (CH) suffers severe damage due to the interaction amongst physical and chem-ical atmospheric factors. To study the mechanisms of degradation and to test the effectiveness of exper-imental protective treatments, accelerated ageing tests and artificial rains are widely used. In a scenario where climate and tropospheric composition are changing, the compositional variation of atmospheric deposition might strongly contribute to a gap between the results obtained in laboratory and real-world outdoor exposure. To reduce this gap, updated synthetic solutions, representative of changed deposition, seem necessary for material testing so to set up better conservative strategies.This study provides new formulations of ageing solutions representative of changed deposition in southern Europe, obtained through the analysis of trends and sources of ions in atmospheric bulk de-positions (1997-2019 period) collected in a highly polluted area (Po Valley, Italy).(c) 2022 Consiglio Nazionale delle Ricerche (CNR). Published by Elsevier Masson SAS. All rights reserved.

The paper shows how the aeronautical heritage is affected by airborne pollutants and the air temperature-humidity complex. Monitoring meteorological and environmental data in a heritage site intended for protection, these effects are analyzed. The starting point is thus the acquisition of the meteorological and environmental data from the intended hangar with stored historical aircrafts taken part in fights of the second world war. The following step is an evaluation of the penetration of moisture into the hangar environment from outside. This moisture penetration is deducted from wet/dry cycles obtained from air humidity and temperature fluctuations in the hangar environment. In addition, an evolution of the aircraft surface temperature is pertinent to potential moisturizing the aircraft surface. As a measure of moisture penetration, a time of wetness (ToW) is determined indoors. Furthermore, pollutants infiltrated into the hangar environment are derived from a standardized methodology. Beside the pollution infiltration, the indoor generated pollution is estimated per material from which the historic aircrafts are constituted. Because of major material in the aircraft, the deposition rate of indoor pollutants onto an aluminum alloy is determined by means of a standardized statistical model. Finally, monitoring the hangar environment, the heritage aircraft vulnerability to corrosion is estimated based on atmosphere corrosivity modeling.

The San Carlo Colossus, known as San Carlone, is a monument constituted by an internal stone pillar support to which a wrought iron structure is attached. Embossed copper sheets are fixed to the iron structure to give the final shape to the monument. After more than 300 years of outdoor exposure, this statue represents an opportunity for an in-depth investigation of long-term galvanic coupling between wrought iron and copper. Most iron elements of the San Carlone appeared in good conservation conditions with scarce evidence of galvanic corrosion. In some cases, the same iron bars presented some portions in good conservation conditions and other nearby portions with active corrosion. The aim of the present study was to investigate the possible factors correlated with such mild galvanic corrosion of wrought iron elements despite the widespread direct contact with copper for more than 300 years. Optical and electronic microscopy and compositional analyses were carried out on representative samples. Furthermore, polarisation resistance measurements were performed both on-site and in a laboratory. The results revealed that the iron bulk composition showed a ferritic microstructure with coarse grains. On the other hand, the surface corrosion products were mainly composed of goethite and lepidocrocite. Electrochemical analyses showed good corrosion resistance of both the bulk and surface of the wrought iron, and galvanic corrosion is not occurring probably due to the iron's relatively noble corrosion potential. The few areas where iron corrosion was observed are apparently related to environmental factors, such as the presence of thick deposits and to the presence of hygroscopic deposits that create localized microclimatic conditions on the surface of the monument.

The paper deals with monitoring and analyzing the indoor environmental parameters through remote data collection to evaluate the pollution and moisture infiltration effects on aircraft heritage conservation. First, based on the meteorological and pollution data, the moisture penetration and airborne pollution infiltration into indoor spaces of a heritage site (hangar) with stored historic aircrafts are determined. The hangar under investigation is located in the Aviation museum Kbely, Prague, Czech Republic. The determination is performed by wet/dry cycles (fluctuations) evaluation and applying ISO 11844 methodology to outdoor pollution infiltration into the interior. Next, a time of wetness (ToW) is determined indoors according to ISO 9223, rather as an environmental than a surface parameter as dewing and exceeding high humidity level (approxl RH 80% at T>0 °C) are considered. The actual moisture adsorption onto polluted surfaces of aircraft artifacts is then dependent on the hygroscopic corrosion products developed. Such an adsorption prolongs actual surface ToW. In addition to ToW, even the deposition rate of indoor pollutants, particularly sulphur dioxide and chlorides, are considered and the atmosphere corrosivity is estimated by applying the ISO standardized statistical models for aluminium. The resulting iso-corrosivity figures out the aggressiveness of the hangar environment from the point of view of aircraft material susceptibility to corrosion and degradation.

Silicon bronze is widely used for monuments: corrosion of Cu-3Si-1Mn was studied with respect to Cu-5Sn-5Zn-5Pb during ageing tests (runoff/full immersion) in acid rain. Surface characterisation (FEG-SEM/EDS elaborated through PCA, TEM, Raman, FTIR, profilometry), metal release and EIS measurements were performed. Under runoff conditions, where mechanical action plays a role, the alloys showed comparable corrosion resistance. In full immersion the corrosion rate of Cu-3Si-1Mn was slightly higher than that of Cu-5Sn-5Zn-5Pb, due to the different nature of the corrosion products. Results showed that, compared to Sn oxide/hydroxide, Si tends to form less protective amorphous products, detaching from the surface.

Epilithic bacteria play a fundamental role in the conservation of cultural heritage (CH) materials. On stones, bacterial communities cause both degradation and bioprotection actions. Bronze biocorrosion in non-burial conditions is rarely studied. Only few studies have examined the relationship between bacteria communities and the chemical composition of patinas (surface degradation layers). A better comprehension of bacterial communities growing on our CH is fundamental not only to understand the related decay mechanisms but also to foresee possible shifts in their composition due to climate change. The present study aims at (1) characterizing bacterial communities on bronze and marble statues; (2) evaluating the differences in bacterial communities' composition and abundance occurring between different patina types on different statues; and (3) providing indications about a representative bacterial community which can be used in laboratory tests to better understand their influence on artefact decay. Chemical and biological characterization of different patinas were carried out by sampling bronze and marble statues in Bologna and Ravenna (Italy), using EDS/Raman spectroscopy and MinION-based 16SrRNA sequencing. Significant statistical differences were found in bacterial composition between marble and bronze statues, and among marble patinas in different statues and in the same statue. Marble surfaces showed high microbial diversity and were characterized mainly by Cyanobacteria, Proteobacteria and Deinococcus-Thermus. Bronze patinas showed low taxa diversity and were dominated by copper-resistant Proteobacteria. The copper biocidal effect is evident in greenish marble areas affected by the leaching of copper salts, where the bacterial community is absent. Here, Ca and Cu oxalates are present because of the biological reaction of living organisms to Cu ions, leading to metabolic product secretions, such as oxalic acid. Therefore, a better knowledge on the interaction between bacteria communities and patinas has been achieved.

Application of protective coatings is the most widely used conservation treatment for outdoor bronzes. Eco-friendly and non-hazardous coatings are currently needed for conservation of outdoor bronze monuments. To fulfil this need, the M-ERA.NET European research project B-IMPACT (Bronze-IMproved non-hazardous PAtina CoaTings) aimed at assessing the protectiveness of innovative coatings for historical and modern bronze monuments exposed outdoors. In this project, two bronze substrates (historical Cu-Sn-Zn-Pb and modern Cu-Si-Mn alloys) were artificially patinated, by acid rain solution using dropping test and by "liver of sulphur" procedure (K2S aqueous solution) to obtain black patina, respectively. Subsequently, the application of several newly developed protective coatings was carried out and their performance was investigated by preliminary electrochemical tests. In the following steps of the work, the assessment of the best-performing coatings was carried out and their performance was compared to Incralac, one of the most widely used protective coatings in conservation practice. A multi-analytical approach was adopted, considering artificial ageing (carried out in representative conditions, including exposure to rain runoff, stagnant rain and UV radiation) and metal release, as well as visual aspect (so as to include aesthetical impact among the coating selection parameters) and morphological and structural evolution of the coated surfaces due to simulated outdoor exposure. Lastly, also the health impact of selected coatings was assessed by occupational hazard tests. The removability and re-applicability of the best-performing coatings were also assessed. The best alternatives to the conventional Incralac exhibited were: (i) fluoroacrylate blended with methacryloxy-propyl-trimethoxy-silane (FA-MS) applied on patinated Cu-Sn-Zn-Pb bronze and (ii) 3-mercapto-propyl-trimethoxysilane (PropS-SH) applied on patinated Cu-Si-Mn bronze.