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Kosec T.,Slovenian National Building And Civil Engineering Institute | Legat A.,Slovenian National Building And Civil Engineering Institute | Ropret P.,Institute for the Protection of the Cultural Heritage of Slovenia | Ropret P.,Smithsonian Institution
Journal of Raman Spectroscopy | Year: 2014

Bronze surfaces, as well as prepatinated surfaces on bronze, undergo chemical and visual changes when exposed to humid and polluted environments. For this reason, it is important to study the effectiveness of corrosion inhibitors on patinatedbronze surfaces. The aim of this study was to investigate different protection systems for patinated bronze, which are based on the use of two azole type inhibitors: 2-mercaptobenzimidazole and benzotriazole. The results of our practice confirmed that these inhibitors were very effective when immersed in a corrosive solution containing inhibitor for 24h. The inhibited layers were then protected by a water-repellant layer. In the case of the studied patinas, green chloride and green nitrate patinas, applied over the brown artist's patina, were tested, as well as brown patina and the patina that develops on bare bronze. The study was performed after each chemical patination and the application of the two different inhibitors. The inhibition systems used on the different chemically achieved patinas were characterized by Raman spectroscopy and electrochemical techniques. The results of the Raman studies showed a chemical interaction of both inhibitors with copper and bronze but a versatile interaction between the inhibitors and the different patinas. The chemical interaction of benzotriazole was observed on the nitrate patina, whereas the mercaptobenzimidazole showed interaction also with the chloride-type patina. Electrochemical tests proved the interaction, which had been detected by Raman spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd. Source


Ropret P.,Institute for the Protection of the Cultural Heritage of Slovenia | Ropret P.,Smithsonian Institution | Kosec T.,Slovenian National Building And Civil Engineering Institute
Journal of Raman Spectroscopy | Year: 2012

In humid air, copper and its high copper alloys (bronze) tend to form an oxide layer (patina). Natural patinas protect copper and its alloys from further corrosion processes. On the other hand, artists have frequently deliberately patinated bronze for visual effects. Thus, it is of great importance to study the patina changing mechanism to follow its chemical changes and to predict in advance the likely corrosion processes. Green chloride and green nitrate patinas, applied over the brown artist's patina, were tested, and also brown patina and the patina that develops on bare bronze. The Raman spectra were studied after chemical patination, and after exposing the patina samples in a climatic chamber, which can produce an environment that resembles an industrial atmosphere, for 12 weeks. The structures of the patinas and of the corrosion products were characterized by scanning electron microscopy, Raman spectroscopy and X-ray diffraction. Cuprite and cuprous sulfite were found on the brown patina, atacamite on the green chloride patina, and a mixture of gerhardite and rouaite on the blue to green nitrate type patina. After 12 weeks of exposure to humidity, a controlled concentration of SO 2, and salt spray mist, the corrosion products changed. In general, clinoatacamite and paratacamite are the end corrosion products, after an intermediate brochantite stage on the green chloride and green nitrate type patinas. The end products of each patina type are given. Copyright © 2012 John Wiley & Sons, Ltd. Source


Kosec T.,Slovenian National Building And Civil Engineering Institute | Ropret P.,Institute for the Protection of the Cultural Heritage of Slovenia | Ropret P.,Smithsonian Institution | Legat A.,Slovenian National Building And Civil Engineering Institute
Journal of Raman Spectroscopy | Year: 2012

Patinas form spontaneously on copper and high copper alloys when exposed to humidity and air. They usually protect the underlying metal from corrosion. Bronze is often chemically patinated by artists to achieve an antique appearance. However, in the case of chemical patinations on bronze, there is a lack of studies about their change over time during exposure to different types of environments. Recent types of bronze, brown patina and two green type patinas (green chloride and green nitrate patina) applied over a brown patina, were selected for testing. The aim of the present study was to monitor the transformation process of chemically formed patinas and of the bronze itself after exposure to simulated urban acid rain, for a period of 35 days. The structures of the patina and corrosion products were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Three differently coloured patinas were scraped off from the bronze statue of the poet France Prešeren, two green type patinas and one brown type, to predict the probable influences of the environment, the base alloy and previously used patination techniques. Copyright © 2012 John Wiley & Sons, Ltd. Source


Rogan Smuc N.,University of Ljubljana | Dolenec M.,University of Ljubljana | Lux J.,Institute for the Protection of the Cultural Heritage of Slovenia | Kramar S.,University of Ljubljana | Kramar S.,Slovenian National Building And Civil Engineering Institute
Environmental Earth Sciences | Year: 2014

This study is a geochemical analytical approach to the characterization of pottery samples from an archaeological site near Mošnje (Slovenia). Inductively coupled plasma-mass spectrometry and statistical analyses were used to determine detailed geochemical properties of the pottery sherds and to identify potentially individual groups among the samples studied. The geochemical results indicated the existence of four major groups of the pottery sherds: the first and second groups are assembled from eight samples, all generally characterized by their high CaO and TOT/C content; the third group comprised the samples with the highest SiO2 concentrations; and the fourth group is represented by the samples K3, K5 and K13. The principal component analysis and cluster analysis validated the existing groups and revealed a high degree of chemical similarity between these groups. The geochemical and statistical data confirmed the archaeologists' hypothesis and interpretation of a similar origin/alteration of source material/probable local ceramic production for the majority of the pottery sherds; the imported origin of samples K3 and K13 was recognized, while sample K5 had been intentionally imported as a sample for comparative purposes. © 2013 Springer-Verlag Berlin Heidelberg. Source


Kramar S.,Institute for the Protection of the Cultural Heritage of Slovenia | Zalar V.,University of Ljubljana | Urosevic M.,University of Granada | Korner W.,University of Vienna | And 4 more authors.
Materials Characterization | Year: 2011

This study deals with the characterization of mortars collected from bath complex of the Roman villa rustica from an archeological site near Mošnje (Slovenia). The mortar layers of the mosaics, wall paintings and mortar floors were investigated. A special aggregate consisting of brick fragments was present in the mortars studied. The mineralogical and petrographic compositions of the mortars were determined by means of optical microscopy, X-ray powder diffraction and FTIR spectroscopy. Analysis of aggregate-binder interfaces using SEM-EDS revealed various types of reactivity rims. In order to assess the hydraulic characteristics of the mortars, the acid-soluble fractions were determined by ICP-OES. Furthermore, the results of Hg-porosimetry and gas sorption isotherms showed that mortars with a higher content of brick fragments particles exhibited a higher porosity and a greater BET surface area but a lower average pore diameter compared to mortars lacking this special aggregate. © 2011 Elsevier Inc. All rights reserved. Source

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