Cristina Chiavari

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.

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.

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 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.