Investigation of Cl corrosion products of iron archaeological artefacts using micro-focused synchrotron X-ray absorption spectroscopy

Synchrotron-based micro-X-ray absorption spectroscopy is used in the present study to obtain chemical information at the microscopic scale such as coordination and oxidation state of Fe atoms in phases constituting corrosion products within archaeological iron artefacts buried in soil. This technique is required in order to answer questions about the iron corrosion process related to the presence of chloride, particularly for restoration and conservation of metallic artefacts of the cultural heritage. The samples available for X-ray microprobe analyses are cross sections from corroded iron archaeological objects. Previously, complementary techniques have been used such as μXRD and μRaman. This specific study applies micro-X-ray absorption spectroscopy to determine the spatial variation of the predominant Fe oxidation state and to identify the corresponding crystallographic phase. The analyses performed at Fe and Cl K-edges (μXANES) reveal the correlation between the valence distribution in the corrosion products and the evolution of the chloride concentration. In addition to the presence of the well-known iron oxyhydroxide β-FeOOH: akaganeite, we highlight the presence of another important phase, the β-Fe₂(OH)₃Clhydroxychloride. These important findings help to gain new insights concerning the influence of such phases in the iron corrosion mechanism within their precise characterization. PACS 61.10.Ht; 61.10.-i; 68.49.Uv     

Raman study of a deuterated iron hydroxycarbonate to assess long‐term corrosion mechanisms in anoxic soils

In several contexts such as cultural heritage, oil and gas or nuclear waste disposal, the long‐term corrosion mechanisms of iron in anoxic soils are studied. For this purpose, corrosion layers formed on ferrous archaeological artefacts from the site of Glinet (16th century, Normandy, France) were characterised. The main phases identified are siderite (FeCO₃), chukanovite (iron hydroxycarbonate: Fe₂(OH)₂CO₃ and magnetite (Fe₃O₄). In order to provide reliable Raman references for further studies on carbonated systems, the iron hydroxycarbonate (chukanovite) was synthesised on iron discs. The corrosion mechanisms were investigated by re‐corroding the archaeological samples in a deuterated solution. Raman characterisation on cross sections inside the layer revealed the presence of deuterated chukanovite, allowing the deuterium tracing of the spreading of the corrosion. A set of chukanovite samples was synthesised with various D/H ratios. Using these reference data, the proportion of deuterated chukanovite in re‐corroded artefacts was evaluated, and the corrosion rate was estimated as less than 1.6 µm/year. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of archaeological iron objects by PGAA,Mössbauer spectroscopy and X-ray diffraction

Archaeological iron objects often corrode rapidly after their excavation, even though they have survived long times of burial in the ground. Chlorine that accumulates during burial is thought to play a major role in this destructive post-excavation corrosion. It is therefore important for the conservation of such objects to determine the chlorine content in a non-destructive manner and, if necessary, to remove the chlorine from the artefacts by appropriate methods. Such methods are leaching in alkaline solutions or heating in a reducing atmosphere at temperatures up to 800 ^°C. We have studied the efficiency of the heating method using prompt gamma activation analysis (PGAA) for monitoring the Cl content and Mössbauer spectroscopy at room temperature (RT) and 4.2 K as well as X-ray diffraction to study the mineralogical transformations of the rust layers. The heat treatments were performed a N₂/H₂ (90/10) mixture at temperatures up to 750 ^°C. As test specimens sections of iron rods from the Celtic oppidum of Manching (Bavaria) were used. The initial Cl contents of the pieces varied in the range of several hundred ppm, referring to the iron mass. Annealing for 24 h at 350, 550 and 750 ^°C was found to reduce the Cl contents of the specimens, to about 70, 30 and 15 % of the original values, respectively. The rust consists mainly of goethite with admixtures of magnetite, lepidocrocite and akaganeite, which is thought to be a major carrier of chlorine, probably together with iron chlorides. Much of the goethite is so fine-grained that it does not split magnetically at RT. Annealing converts the rust mainly to maghemite at 350 ^°C, to magnetite at 550 ^°C and to wüstite plus magnetite and metallic iron at 750 ^°C. Pure akaganeite behaves in nearly the same manner.     

Characterization of Iron Oxides Commonly Formed as Corrosion Products on Steel

For fundamental studies of the atmospheric corrosion of steel, it is useful to identify the iron oxide phases present in rust layers. The nine iron oxide phases, iron hydroxide (Fe(OH)₂), iron trihydroxide (Fe(OH)₃), goethite (α-FeOOH), akaganeite (β-FeOOH), lepidocrocite (γ-FeOOH), feroxyhite (δ-FeOOH), hematite (α-Fe₂O₃), maghemite (γ-Fe₂O₃) and magnetite (Fe₃O₄) are among those which have been reported to be present in the corrosion coatings on steel. Each iron oxide phase is uniquely characterized by different hyperfine parameters from M?ssbauer analysis, at temperatures of 300K, 77K and 4K. Many of these oxide phases can also be identified by use of Raman spectroscopy. The relative fraction of each iron oxide can be accurately determined from the M?ssbauer subspectral area and recoil-free fraction of each phase. The different M?ssbauer geometries also provide some depth dependent phase identification for corrosion layers present on the steel substrate. Micro-Raman spectroscopy can be used to uniquely identify each iron oxide phase to a high spatial resolution of about 1 μm. This revised version was published online in August 2006 with corrections to the Cover Date.     

Atmospheric corrosion in the Gulf of México

The corrosion products on steels exposed at two sites in Campeche, México and one site at Kure Beach, USA, have been investigated to determine the extent to which different marine conditions and exposure times control the oxide formation. The corroded coupons were analyzed by Mössbauer, Raman and infrared spectroscopy as well as X‐ray diffraction, in order to completely identify the oxides and map their location in the corrosion coating. The coating compositions were determined by Mössbauer spectroscopy using a new parameter, the relative recoilless fraction (F-value) which gives the atomic fraction of iron in each oxide phase from the Mössbauer sub‐spectral areas. For short exposure times, less than three months, an amorphous oxyhydroxide was detected after which a predominance of lepidocrocite (γ-FeOOH), and akaganeite (β-FeOOH) were observed in the corrosion coatings with the fraction of the later phase increasing at sites with higher atmospheric chloride concentrations. The analysis also showed that small clusters of magnetite (Fe₃O₄), and maghemite (γ(Fe₂O₃), were seen in the micro-Raman spectra but were not always identified by Mössbauer spectroscopy. For longer exposure times, goethite (α-FeOOH), was also identified but little or no β-FeOOH was observed. It was determined by the Raman analysis that the corrosion products generally consisted of inner and outer layers. The protective layer, which acted as a barrier to slow further corrosion, consisted of the α-FeOOH and nano-sized γ-Fe₂O₃ phases and corresponded to the inner layer close to the steel substrate. The outer layer was formed from high γ-FeOOH and low α-FeOOH concentrations.     

Characterization of initial atmospheric corrosion of conventional weathering steels and a mild steel in a tropical atmosphere

The phases and compositions of the corrosion products of a mild steel (A-36) and two weathering steels (A-588 and COR 420) formed after 3 months exposure to the tropical marine atmosphere of Panama were examined using FTIR and Mössbauer spectroscopy. The results show that amorphous or crystallized iron oxyhydroxides goethite α-FeOOH and lepidocrocite γ-FeOOH are early corrosion products. Maghemite γ-Fe₂O₃ and magnetite Fe₃O₄ have also been identified and found to be prominent components for steels exposed to the most aggressive conditions. The formation of akaganeite β-FeOOH was observed when chlorides were occluded within the rust. FTIR showed the presence of hematite α-Fe₂O₃ in one sample.     

Chemical corrosion by chlorides on ancient-like bronzes and treatment by hydrogen glow discharge plasma

Three representative ancient-like bronzes are employed for the chemical synthesis of Cu₂(OH)₃Cl rich patinas in order to study the influence of the alloying elements in the evolution of the chloride attack and to further conduct stabilization treatment via Hydrogen Glow Discharge Plasma (HGDP) at low temperature and pressure. The corrosion behavior of specimens having Sn and Pb as main alloying elements is governed by a decuprification mechanism and by the formation of Sn–Pb–O enriched barrier layers. In the case of the Zn containing alloy, dezincification is more pronounced at the corrosion initial stages, and copper species predominate the corrosion products evolution. A three-hour HGDP treatment leads to Cu⁺ production and metallic Cu, Sn, Zn, and Pb redeposition, as a result of metal cation reduction. This process is accompanied by partial removal of Cl species, O diminution, and change in coloration. The further increase of the Cl/O atomic ratio measured on the post-treated surfaces leads to the formation of nantokite and thus to the conclusion that the stabilization of objects with extensive Cl attack is not feasible by HGDP without preliminary chemical treatment.     

The growth of the passive film on iron in 0.05 M NaOH studied in situ by Raman micro‐spectroscopy and electrochemical polarisation. Part I: near‐resonance enhancement of the Raman spectra of iron oxide and oxyhydroxide compounds

Raman spectroscopy, in principle, is an excellent technique for the study of molecular species developed on metal surfaces during electrochemical investigations. However, the use of the more common laser wavelengths such as the 514.5‐nm line results in spectra of less than optimal intensity, particularly for iron oxide compounds. In the present work, near‐resonance enhancement of the Raman spectra was investigated for the iron oxide and iron oxyhydroxide compounds previously reported to be present in the passive film on iron, using a tuneable dye laser producing excitation wavelengths between 560 and 637 nm. These compounds were hematite (α‐Fe₂O₃), maghemite (γ‐Fe₂O₃), magnetite (Fe₃O₄), goethite (α‐FeOOH), akaganeite (β‐FeOOH), lepidocrocite (γ‐FeOOH) and feroxyhyte (δ‐FeOOH). Optimum enhancement, when compared to that with the 514.5‐nm line, was obtained for all the iron oxide and oxyhydroxide standard samples in the low wavenumber region (<1000 cm⁻¹) using an excitation wavelength of 636.4 nm. Particularly significant enhancement was obtained for lepidocrocite, hematite and goethite. Copyright © 2010 John Wiley & Sons, Ltd.     

Portable Raman study on the conservation state of four CorTen steel‐based sculptures by Eduardo Chillida impacted by urban atmospheres

Weathering steel, and particularly CorTen steel, is a very used material for modern artworks exhibited outdoors. One of the characteristic that makes this material so attractive to artists is the property to develop a protective rust layer composed by iron oxides which preserves its metallic core from atmospheric corrosion. This study was conducted to evaluate the conservation state of four CorTen sculptures by Eduardo Chillida, located in different places of Bilbao city (north of Spain) and affected by different factors (environmental among others) by using Raman spectroscopy. Measurements were performed in situ with a handheld Raman spectrometer mounted on a tripod with x–y–z axes motorization at the micron level. The most common oxyhydroxides detected were lepidocrocite (γ‐FeO(OH)), goethite (α‐FeO(OH)), hematite ( ‐Fe₂O₃) and magnetite (Fe₃O₄), being goethite the most stable phase. All the iron oxyhydroxides were identified in all of the studied sculptures but their relative amounts were different for each sculpture. The consequences of the marine aerosols exposure in the steel surface were also studied, detecting limonite (FeO(OH)·nH₂O) and akaganeite (β‐FeO(OH)). The results confirmed that the evolution of the rust layer present on the analyzed weathering steels is different, depending both on the exposure and the particular type of the steel. Copyright © 2012 John Wiley & Sons, Ltd.     

Indoor atmospheric corrosion of conventional weathering steels in the tropical atmosphere of Panama

One year indoor atmospheric corrosion examinations have been carried out on two conventional weathering steels for a year, at two test sites, Tocumen and Sherman Breakwater in Panama. They are environmentally classified by ISO 9223 as S₁P₀ τ ₄ and S₃P₀ τ ₅, respectively. In this humid-tropical marine climate corrosion rates are rather high, especially at Sherman Breakwater test site, mainly due to the high deposition of chloride, among other environmental conditions. Our results indicate that indoor corrosion is highly determined by the time of wetness and chloride ions. A-588 weathering steel corroded at a generally lower rate than COR-420 weathering steel. Rust characterization was performed by XRD, FTIR, and Mössbauer spectroscopy. Lepidocrocite, goethite, maghemite and akaganeite were found as corrosion products. Akaganeite is only detected when high chlorides deposition rates are obtained, and no washing effect occurs. This phase, together with maghemite, is obtained when there is greater aggressiveness in the environment.     

Exchange‐Biased Fe3−xO4‐CoO Granular Composites of Different Morphologies Prepared by Seed‐Mediated Growth in Polyol: From Core–Shell to Multicore Embedded Structures

Magnetically contrasted granular hetero‐nanostructures are prepared by seed‐mediated growth in polyol, properly combining two oxide phases with different magnetic order, ferrimagnetic (F) partially oxidized magnetite Fe_3−xO₄ and antiferromagnetic (AF) cobalt oxide. Spinel Fe_3−xO₄ nanoparticles are first synthesized and then used as seeds for rock salt CoO nanocrystals growth. Three different hetero‐nanostructure designs are realized, acting on the content ratio between the seeds and the deposit's precursors during the synthesis. For all of them, the spinel and the rock salt phases are confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. Both phases are obtained in high‐crystalline quality with a net epitaxial relationship between the two crystallographic lattices. Mössbauer spectrometry confirms the cobalt cation diffusion into the spinel seeds, giving favorable chemical interfacing with the rock salt deposit, thus prevailing its heterogeneous nucleation and consequently offering the best condition for exchange‐bias (EB) onset. Magnetic measurements confirm EB features. The overall magnetic properties are found to be a complex interplay between dipolar interactions, exchange anisotropy at the F/AF interface, and magnetocrystalline anisotropy enhancement in the F phase, due to Co²⁺ diffusion into iron oxide's crystalline lattice. These results underline the powerfulness of colloidal chemistry for functional granular hetero‐nanostructured material processing.     

Competing energy scales in high‐temperature superconductors: Ultrafast pump–probe studies

We present a review of photoexcited quasiparticle dynamics of cuprate and pnictide high‐temperature superconductors in regimes (temperature, doping) where different phases such as superconductivity, spin‐density‐wave (SDW) and pseudogap phases coexist or compete with one another. We start with the overdoped cuprate superconductor Y_1–xCa_x Ba₂Cu₃O_7–δ, where the superconducting gap and pseudogap coexist in the superconducting state. In another cuprate Tl₂Ba₂Ca₂Cu₃O_y, we ob‐ serve a competition between SDW and superconducting orders deep in the superconducting state. Finally, in the underdoped iron pnictide superconductor (Ba,K)Fe₂As₂, SDW order forms at 85 K, followed by superconductivity at 28 K. We also find the emergence of a normal‐state order that suppresses SDW at a temperature T * ～ 60 K and argue that this normal‐state order is a precursor to superconductivity. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the Rust Products Formed on Weathering and Carbon Steels Exposed to Chloride in Dry–Wet Cyclical Processes

The rust products formed on weathering and carbon steels exposed to dry–wet cyclical processes in different chloride-rich solutions are carefully examined by means of different techniques. Special emphasis is given to the methodology of analysis of the data using 300 K and 77 K Mössbauer spectrometry and X-ray diffraction. The rust that is loosely bound to the metal surface and that it is lost during the corrosion process, for both types of steel, was found to be composed of lepidocrocite, superparamagnetic goethite, hematite, and traces of akaganeite. On the other hand, the adherent rust, which is differentiated as scraped and hit according to the way it is obtained, from both steels was found to be composed of akaganeite, spinel phase, goethite exhibiting broad distribution of particle sizes and lepidocrocite. The relative abundances of rust components for both steels were very similar, suggesting similar corrosion processes. Mass loss measurements show that the corrosion rates increases with increasing the chloride concentration. The presence of large quantities of spinel phase and akaganeite are a consequence of a corrosion process under the influence of very high chloride concentrations. Our results are useful for assessing the behavior of weathering steels where the levels of chlorides are high or in contact with sea water.     

Palladium‐catalyzed cyclization of 2‐alkynyl‐N‐ethanoyl anilines to indoles: synthesis,structural, spectroscopic,and mechanistic study

This study reports a facial regio‐selective synthesis of 2‐alkyl‐N‐ethanoyl indoles from substituted‐N‐ethanoyl anilines employing palladium (II) chloride, which acts as a cyclization catalyst. The mechanistic trait of palladium‐based cyclization is also explored by employing density functional theory. In a two‐step mechanism, the palladium, which attaches to the ethylene carbons, promotes the proton transfer and cyclization. The gas‐phase barrier height of the first transition state is 37 kcal/mol, indicating the rate‐determining step of this reaction. Incorporating acetonitrile through the solvation model on density solvation model reduces the barrier height to 31 kcal/mol. In the presence of solvent, the electron‐releasing (–CH₃) group has a greater influence on the reduction of the barrier height compared with the electron‐withdrawing group (–Cl). These results further confirm that solvent plays an important role on palladium‐catalyzed proton transfer and cyclization. For unveiling structural, spectroscopic, and photophysical properties, experimental and computational studies are also performed. Thermodynamic analysis discloses that these reactions are exothermic. The highest occupied molecular orbital?lowest unoccupied molecular orbital gap (4.9–5.0 eV) confirms that these compounds are more chemically reactive than indole. The calculated UV–Vis spectra by time‐dependent density functional theory exhibit strong peaks at 290, 246, and 232 nm, in good agreement with the experimental results. Moreover, experimental and computed ¹H and ¹³C NMR chemical shifts of the indole derivatives are well correlated. Copyright © 2015 John Wiley & Sons, Ltd.     

Micellar effects on aromatic nucleophilic substitution by the ANRORC mechanism. Hydrolysis of 2‐chloro‐3,5‐dinitropyridine

The hydrolysis of 2‐chloro‐3,5‐dinitropyridine by sodium hydroxide in the presence of micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl) and sodium dodecyl sulfate (SDS) has been studied. The reaction follows a consecutive reaction path involving the formation of a long‐lived intermediate 3 and finally giving the product, 3,5‐dinitro 2‐pyridone 2 . The mechanism follows an addition of the nucleophile, ring opening and ring closure (ANRORC) reaction path. The rate constant was observed to be first‐order dependent on [OH^?]. The rate of reaction increased on increasing [CTABr] and, after reaching to the maxima, it started decreasing. The anionic SDS micelles inhibited the rate of hydrolysis. The results of the kinetic experiments were treated with the help of the pseudophase ion exchange model and the Menger–Portnoy model. The added salts, viz. NaBr, Na‐toluene‐4‐sulphonate, and (CH₃)₄NBr on varying [CTACl] and [SDS] inhibited the rate of reaction. The various kinetic parameters in the presence and absence of salts were determined and are reported herewith. Copyright © 2011 John Wiley & Sons, Ltd.     

Micro‐Raman investigations of early stage silver corrosion products occurring in sulfur containing atmospheres

Silver is a soft, lustrous metal with the highest electrical and thermal conductivity. Due to these properties, it has many applications as a precious material both in pure and alloy form (ornaments, jewellery, utensils, coins), but also in several technological fields, considering silver compounds (e.g. photography, electric and electronic industry). As a consequence of this, silver and its by‐products are regularly exposed to different atmospheres where a wide spectrum of agents (e.g. moisture, temperature, air pollutants, UV light) may cause metal corrosion and alteration of their surface characteristics and properties. The aim of this research is to deepen the potential and applicability of micro‐Raman spectroscopy as a surface‐sensitive technique to investigate the initial steps of atmospheric corrosion throughout the identification of surface chemical reactions and corrosion products formed on silver substrates. In a previous study, micro‐Raman analysis was carried out on pure silver powder compounds, selected among the most expected corrosion products occurring on silver substrates, in order to optimize experimental conditions and to obtain reference spectra ^[1]. Subsequently highly pure silver samples were exposed for 24 h to different controlled laboratory atmospheres (synthetic air, relative humidity, SO₂, H₂S), particularly focusing on sulfur containing gases, and the resulting surface reactions. The experiments highlight micro‐Raman spectroscopy as a highly surface‐sensitive technique enabling to detect both adsorbed chemical species and crystalline corrosion products of only several monolayers of thickness. Furthermore, these investigations could show the trends of primary and secondary corrosion mechanisms and their mutual interaction occurring on silver substrates. Copyright © 2013 John Wiley & Sons, Ltd.     

Lattice dynamics of Al‐containing MAX‐phase carbides: a first‐principle study

A systematic study on lattice dynamics of M_{n + 1}AlC_n (n = 1–3) phases using first‐principle calculations is reported, where the Raman‐active and infrared‐active (IR) modes are emphasized. The highest phonon wavenumber is related to the vibration of C atoms. The ‘imaginary wavenumber’ in the phonon spectrum of Nb₃AlC₂ contributes to the composition gap in Nb‐Al‐C system (Nb₂AlC and Nb₄AlC₃ do appear in experiments, but there are no experimental reports on Nb₃AlC₂). The full set of Raman‐active and IR‐active modes in the 211, 312, and 413 M_{n + 1}AX_n phases is identified, with the corresponding Raman and IR wavenumbers. The 211, 312, and 413 M_{n + 1}AX_n phases have 4, 6, and 8 IR‐active modes, respectively. There is no distinct difference among the wavenumber ranges of IR‐active modes for 211, 312, and 413 phases, with the highest wavenumber of 780 cm⁻¹ in Ta₄AlC₃. The Raman wavenumbers of M₂AlC phases all decrease with increasing the d‐electron shell number of transition metal M. However, this case is valid only for the Raman‐active modes with low wavenumbers of M₃AlC₂ and M₄AlC₃. Copyright © 2015 John Wiley & Sons, Ltd.     

Della Robbia blue glaze: micro‐Raman temperature study and X‐ray fluorescence spectroscopy characterization

Micro‐Raman temperature study and X‐ray fluorescence (XRF) spectroscopy were used for characterization of the blue glaze on Saint John the Baptist—majolica terracotta relief attributed to Andrea Della Robbia and Saint John the Baptist with Cross—majolica terracotta statue attributed to Giovanni Della Robbia. Both objects are on permanent exhibition in the John and Mable Ringling Museum of Art in Sarasota, FL. This study proves that the detection of the 548 cm⁻¹ Raman band alone cannot serve as evidence for presence of lazurite crystallites in the pigment in the glaze. It was established that the famous Della Robbia blue is due to the combined effect of Co Ni Cu Zn atoms and S₃⁻ ions embedded in a lead silicate matrix. It is proposed that the Della Robbia family used Co‐containing sulfide ores as a source for manufacturing their blue pigments. Copyright © 2009 John Wiley & Sons, Ltd.     

Probing Ag nanoparticle surface oxidation in contact with (in)organics: an X‐ray scattering and fluorescence yield approach

Characterizing interfacial reactions is a crucial part of understanding the behavior of nanoparticles in nature and for unlocking their functional potential. Here, an advanced nanostructure characterization approach to study the corrosion processes of silver nanoparticles (Ag‐Nps), currently the most highly produced nanoparticle for nanotechnology, is presented. Corrosion of Ag‐Nps under aqueous conditions, in particular in the presence of organic matter and halide species common to many natural environments, is of particular importance because the release of toxic Ag⁺ from oxidation/dissolution of Ag‐Nps may strongly impact ecosystems. In this context, Ag‐Nps capped with polyvinolpyrrolidone (PVP) in contact with a simple proxy of organic matter in natural waters [polyacrylic acid (PAA) and Cl^? in solution] has been investigated. A combination of synchrotron‐based X‐ray standing‐wave fluorescence yield‐ and X‐ray diffraction‐based experiments on a sample consisting of an approximately single‐particle layer of Ag‐Nps deposited on a silicon substrate and coated by a thin film of PAA containing Cl revealed the formation of a stable AgCl corrosion product despite the presence of potential surface stabilizers (PVP and PAA). Diffusion and precipitation processes at the Ag‐Nps–PAA interface were characterized with a high spatial resolution using this new approach.     

Non‐destructive characterization of 17th century painted silk banner by the combined use of Raman and XRF portable systems

X‐ray fluorescence spectroscopy (XRF) and Raman spectroscopy analysis were performed to examine a 17th century painted silk banner in order to characterize the pigments and materials used. This complementary approach yields information on the elemental (XRF) and on the molecular composition (Raman) of the used compounds. The paint layer, ground layer under gilding, and gilding layer were investigated. For the studied object, vermilion (HgS), lead white (2PbCO₃ · Pb(OH)₂), red lead (Pb₃O₄), and aurichalcite ((Cu,Zn)₅(CO₃)₂(OH)₆) were found. The presence of silver and gold foils was confirmed. The techniques used in the analysis were portable, non‐destructive, and non‐invasive, which is very desirable when analyzing cultural heritage objects. The obtained results were used by the conservators to develop a showcase prototype for safe exhibition. Copyright © 2015 John Wiley & Sons, Ltd.