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Tadeja Kosec - One of the best experts on this subject based on the ideXlab platform.
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Development of multi-component fluoropolymer based coating on simulated outdoor Patina on quaternary bronze
Progress in Organic Coatings, 2019Co-Authors: Tadeja Kosec, Cristina Chiavari, Luka Škrlep, Erika Švara Fabjan, Adrijana Sever Škapin, Giulia Masi, Elena Bernardi, Claudie Josse, Jérôme Esvan, Luc RobbiolaAbstract:Abstract Bronze reacts with oxygen, humidity, and pollutants in the atmosphere so that a Patina forms. Natural exposure to an outdoor atmosphere can be simulated and accelerated in order to achieve a Patina that mimics outdoor ancient Patina. In order to avoid the uncontrolled dissolving of either the natural or artificially formed Patina, protection of the Patina is needed. In this study, a multi-component fluoropolymer based coating for the protection of bronze Patina was developed. In order to provide various functionalities of the coating (such as the hydrophobicity of the coating surface, obtaining interactions within the coating itself as well as a bronze substrate and inhibiting the corrosion processes), a fluoroacrylate coating with appropriate adhesion promoter was suggested, with and without a silane modified benzotriazole inhibitor. The protective efficiency and durability of the applied coatings were investigated electrochemically using potentiodynamic tests and electrochemical impedance spectroscopy in a simulated acid rain solution. All of the developed coatings showed a significant decrease in the corrosion current density. The self-assembled single layer coating (FA-MS) also showed 100% inhibition efficiency. After ageing the coating remained transparent and did not change by UV exposure and/or thermal cycling. The Patina and coating investigations using FIB-SEM and EDX showed that the latter coating (FA-MS) successfully covered the surface of the Patinated bronze. The mechanism of the bonding was proposed and supported with the spectroscopic observation of a thin and even coating.
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Raman investigation of artificial Patinas on recent bronze protected by different azole type inhibitors in an outdoor environment
Journal of Raman Spectroscopy, 2014Co-Authors: Tadeja Kosec, Andraž Legat, Polonca RopretAbstract: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 Patinated-bronze 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 24 h. 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.
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raman investigation of artificial Patinas on recent bronze part i climatic chamber exposure
Journal of Raman Spectroscopy, 2012Co-Authors: Polonca Ropret, Tadeja KosecAbstract: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 SO2, 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.
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Raman investigation of artificial Patinas on recent bronze – Part I: climatic chamber exposure
Journal of Raman Spectroscopy, 2012Co-Authors: Polonca Ropret, Tadeja KosecAbstract: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 SO2, 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.
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Raman investigation of artificial Patinas on recent bronze‒part II: urban rain exposure
Journal of Raman Spectroscopy, 2012Co-Authors: Tadeja Kosec, Polonca Ropret, Andraž LegatAbstract: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 Preseren, 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.
Polonca Ropret - One of the best experts on this subject based on the ideXlab platform.
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Raman investigation of artificial Patinas on recent bronze protected by different azole type inhibitors in an outdoor environment
Journal of Raman Spectroscopy, 2014Co-Authors: Tadeja Kosec, Andraž Legat, Polonca RopretAbstract: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 Patinated-bronze 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 24 h. 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.
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raman investigation of artificial Patinas on recent bronze part i climatic chamber exposure
Journal of Raman Spectroscopy, 2012Co-Authors: Polonca Ropret, Tadeja KosecAbstract: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 SO2, 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.
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Raman investigation of artificial Patinas on recent bronze – Part I: climatic chamber exposure
Journal of Raman Spectroscopy, 2012Co-Authors: Polonca Ropret, Tadeja KosecAbstract: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 SO2, 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.
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Raman investigation of artificial Patinas on recent bronze‒part II: urban rain exposure
Journal of Raman Spectroscopy, 2012Co-Authors: Tadeja Kosec, Polonca Ropret, Andraž LegatAbstract: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 Preseren, 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.
Andreu Moya-garra - One of the best experts on this subject based on the ideXlab platform.
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Patinas developed in environmental burial conditions: the Neolithic steles of Reguers de Seró (Lleida, Spain)
Environmental Science and Pollution Research, 2010Co-Authors: Maite Garcia-valles, Meritxell Aulinas, Joan B. López-melción, Andreu Moya-garraAbstract:Background, aim and scope Weathering Patinas in rocks are the result of interaction processes between rock surfaces and atmosphere, biosphere and soil. Therefore, their textural and mineral composition is strongly related to environmental and bioactivity conditions. Whereas the development of weathering Patinas in atmospheric conditions is well documented (e.g. typical Mediterranean Patina), only very few studies focus on their formation in a burial environment. Our study of Patinas developed on the tumular structure of Reguers de Seró deals with the knowledge of burial Patinas from a textural and mineralogical point of view. The aims of this study include: (1) the characterisation of the rock used in this megalithic monument as well as inferences regarding the origin of the raw material; (2) the evaluation of the Patinas developed on the surface of the carved steles; and (3) the discussion of the environmental conditions (atmospheric or burial) that favoured the development of the Patinas. Materials and methods Whole rock and related Patinas (powdered samples and small single pieces) were carefully sampled in five of the seven Neolithic steles discovered during a municipal excavation. Some whole rock samples from the surrounding outcrops were also collected in order to correlate them with the stone forming the megalith. Samples were analysed macroscopically, using a glass binocular, and microscopically, by means of a polarising light microscope and a scanning electron microscope (SEM-EDAX). The mineralogical composition was determined by X-ray diffraction, and a colorimetric analysis was also carried out in all the sampled Patinas. Results The obtained results evidence a strong textural and mineralogical correlation between the whole rock of the megalith and the collected samples of the nearby outcrops; both are classified as calcarenite. A uniformly distributed beige–orange Patina (35–100 μm thick) covering the surface of the steles modifies their aspect. A layer of calcite (micrite) with granular texture was detected in all the sampled Patinas, being the main mineral compositions (∼60–90%). In contrast, a discontinuous external layer (25–50 μm thick) of botryoidally gypsum occurs on only a few Patinas. SEM-EDAX analyses evidenced that Ca is related to several processes, including inorganic processes, as well as to minor bioactivity. Discussion The textural and mineralogical characteristics of the Reguers Patinas differ from typical Mediterranean Patina sequences, suggesting different environmental conditions for their formation. Several arguments supporting the formation of the Reguers Patinas in a burial environment include: (1) Patinas cover the entire surface of the steles, iconograhic motifs and fractures. The uniform colour, texture and composition of the Patinas throughout the steles suggests their development after the construction of the megalithic tomb during a period in which the archaeological site was buried and sealed by the products of the Senill ravine; (2) the absence of heavy metals mainly contained in flying ashes and other depositions from atmospheric dust and pollutants in the micritic Patina; (3) non-appearance of minerals directly formed by biological activity (i.e. oxalates and phosphates); (4) the absence of a well-defined textural sequence (typically of the Mediterranean area) already defined for Patinas developed in an atmospheric environment; and (5) the discontinuous occurrence of an external gypsum layer (only present in a few samples) without the presence of the typical spherules related to atmospheric particulate matter. Conclusions and recommendations The petrographic characteristics of the Neolithic steles of Reguers de Seró show that the raw material came from a nearby outcrop. The formation of beige–orange Patinas is related to a burial environment attending their textural and mineralogical features. The protective role played by these Patinas indicates that no previous treatment of such steles would be necessary on an eventual exhibition in atmospheric conditions. Further in-depth studies, similar to those that already exist for Patinas developed in atmospheric conditions, are recommended in order to better define the petrographic characteristics and mechanisms on the formation of Patinas in burial environments.
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Patinas developed in environmental burial conditions: the Neolithic steles of Reguers de Seró (Lleida, Spain).
Environmental science and pollution research international, 2010Co-Authors: Maite Garcia-valles, Meritxell Aulinas, Joan B. López-melción, Andreu Moya-garraAbstract:Background, aim and scope Weathering Patinas in rocks are the result of interaction processes between rock surfaces and atmosphere, biosphere and soil. Therefore, their textural and mineral composition is strongly related to environmental and bioactivity conditions. Whereas the development of weathering Patinas in atmospheric conditions is well documented (e.g. typical Mediterranean Patina), only very few studies focus on their formation in a burial environment. Our study of Patinas developed on the tumular structure of Reguers de Sero deals with the knowledge of burial Patinas from a textural and mineralogical point of view. The aims of this study include: (1) the characterisation of the rock used in this megalithic monument as well as inferences regarding the origin of the raw material; (2) the evaluation of the Patinas developed on the surface of the carved steles; and (3) the discussion of the environmental conditions (atmospheric or burial) that favoured the development of the Patinas.
Maite Garcia-valles - One of the best experts on this subject based on the ideXlab platform.
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Patinas developed in environmental burial conditions: the Neolithic steles of Reguers de Seró (Lleida, Spain)
Environmental Science and Pollution Research, 2010Co-Authors: Maite Garcia-valles, Meritxell Aulinas, Joan B. López-melción, Andreu Moya-garraAbstract:Background, aim and scope Weathering Patinas in rocks are the result of interaction processes between rock surfaces and atmosphere, biosphere and soil. Therefore, their textural and mineral composition is strongly related to environmental and bioactivity conditions. Whereas the development of weathering Patinas in atmospheric conditions is well documented (e.g. typical Mediterranean Patina), only very few studies focus on their formation in a burial environment. Our study of Patinas developed on the tumular structure of Reguers de Seró deals with the knowledge of burial Patinas from a textural and mineralogical point of view. The aims of this study include: (1) the characterisation of the rock used in this megalithic monument as well as inferences regarding the origin of the raw material; (2) the evaluation of the Patinas developed on the surface of the carved steles; and (3) the discussion of the environmental conditions (atmospheric or burial) that favoured the development of the Patinas. Materials and methods Whole rock and related Patinas (powdered samples and small single pieces) were carefully sampled in five of the seven Neolithic steles discovered during a municipal excavation. Some whole rock samples from the surrounding outcrops were also collected in order to correlate them with the stone forming the megalith. Samples were analysed macroscopically, using a glass binocular, and microscopically, by means of a polarising light microscope and a scanning electron microscope (SEM-EDAX). The mineralogical composition was determined by X-ray diffraction, and a colorimetric analysis was also carried out in all the sampled Patinas. Results The obtained results evidence a strong textural and mineralogical correlation between the whole rock of the megalith and the collected samples of the nearby outcrops; both are classified as calcarenite. A uniformly distributed beige–orange Patina (35–100 μm thick) covering the surface of the steles modifies their aspect. A layer of calcite (micrite) with granular texture was detected in all the sampled Patinas, being the main mineral compositions (∼60–90%). In contrast, a discontinuous external layer (25–50 μm thick) of botryoidally gypsum occurs on only a few Patinas. SEM-EDAX analyses evidenced that Ca is related to several processes, including inorganic processes, as well as to minor bioactivity. Discussion The textural and mineralogical characteristics of the Reguers Patinas differ from typical Mediterranean Patina sequences, suggesting different environmental conditions for their formation. Several arguments supporting the formation of the Reguers Patinas in a burial environment include: (1) Patinas cover the entire surface of the steles, iconograhic motifs and fractures. The uniform colour, texture and composition of the Patinas throughout the steles suggests their development after the construction of the megalithic tomb during a period in which the archaeological site was buried and sealed by the products of the Senill ravine; (2) the absence of heavy metals mainly contained in flying ashes and other depositions from atmospheric dust and pollutants in the micritic Patina; (3) non-appearance of minerals directly formed by biological activity (i.e. oxalates and phosphates); (4) the absence of a well-defined textural sequence (typically of the Mediterranean area) already defined for Patinas developed in an atmospheric environment; and (5) the discontinuous occurrence of an external gypsum layer (only present in a few samples) without the presence of the typical spherules related to atmospheric particulate matter. Conclusions and recommendations The petrographic characteristics of the Neolithic steles of Reguers de Seró show that the raw material came from a nearby outcrop. The formation of beige–orange Patinas is related to a burial environment attending their textural and mineralogical features. The protective role played by these Patinas indicates that no previous treatment of such steles would be necessary on an eventual exhibition in atmospheric conditions. Further in-depth studies, similar to those that already exist for Patinas developed in atmospheric conditions, are recommended in order to better define the petrographic characteristics and mechanisms on the formation of Patinas in burial environments.
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Patinas developed in environmental burial conditions: the Neolithic steles of Reguers de Seró (Lleida, Spain).
Environmental science and pollution research international, 2010Co-Authors: Maite Garcia-valles, Meritxell Aulinas, Joan B. López-melción, Andreu Moya-garraAbstract:Background, aim and scope Weathering Patinas in rocks are the result of interaction processes between rock surfaces and atmosphere, biosphere and soil. Therefore, their textural and mineral composition is strongly related to environmental and bioactivity conditions. Whereas the development of weathering Patinas in atmospheric conditions is well documented (e.g. typical Mediterranean Patina), only very few studies focus on their formation in a burial environment. Our study of Patinas developed on the tumular structure of Reguers de Sero deals with the knowledge of burial Patinas from a textural and mineralogical point of view. The aims of this study include: (1) the characterisation of the rock used in this megalithic monument as well as inferences regarding the origin of the raw material; (2) the evaluation of the Patinas developed on the surface of the carved steles; and (3) the discussion of the environmental conditions (atmospheric or burial) that favoured the development of the Patinas.
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The red–orange Patina developed on a monumental dolostone
Engineering Geology, 2001Co-Authors: S. Valls Del Barrio, Maite Garcia-valles, Trinitat Pradell, M. Vendrell-sazAbstract:Orange and reddish Patinas developed on a dolostone of the cathedral of Lleida (Spain) have been analysed and characterised by XRD, SEM/EDX, ICP/MS, optical microscopy and Mossbauer spectroscopy. From the experimental data, a biologically induced transformation of the dolomite rock forming crystals, which form a dolomitic Patina of micrite size, can be stabilised. Furthermore, the iron oxides as determined by Mossbauer spectroscopy play a role as colouring Patina, together with organic matter from the bioactivity. Erosive and constructive processes, as determined through the SEM observations, lead to aesthetical and microstructural changes in the stone surface.
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Interaction of rock and atmosphere : Patinas on Mediterranean monuments
Environmental Earth Sciences, 1998Co-Authors: Maite Garcia-valles, M. Vendrell-saz, Judit Molera, F. BlazquezAbstract:This paper analyzes – chemically, mineralogically, and petrolographically – the Patinas developed on several Mediterranean monuments made with different stones (siliceous and carbonatic) in order to establish their origin and their evolution under the present environmental conditions, and to evaluate the environmental parameters controling their development. Most of the Patinas show a common sequence of layers, which, from the outer to the inner zone, are: (1) present bioactivity and/or biological remains, (2) gypsum-rich Patina, and (3) calcitic brown to orange Patina. Each one may exhibit different fabrics (from micritic to stromatolitic) and may be more or less continuous and homogeneous. The main mineral components are calcite and gypsum, but Ca-oxalates and Ca-phosphates have also been found associated to biological structures, as well as quartz and clays. The different fabrics and textures have been interpreted as consequence of changes in the environmental conditions which seem to be related to the biological activity, facilitating the growth of different organisms and leading to the development of a deposit with distinct characteristics (fabric, texture, porosity, etc.). The gypsum-rich Patina has been interpreted as a sulphation of the underlying calcitic layer by the action of atmospheric pollutants or as dry or wet deposition from the atmospheric dust. The mineralogy and texture of the Patina is independent of the nature of the underlying rock and only in few cases a micritization process has been observed as interaction between Patina and rock. Recently, the penetration of endolithic microflora produced drillings and the development of a fissuration system parallel to the surface, and thus the detachment of the crust from the rock and even flackening of the rock itself has been observed. Consequently, under the present climatic conditions in the Mediterranean basin, erosion is a more active process than deposition, and the crusts and Patinas show a tendency to disappear from the surface of the monuments.
Andraž Legat - One of the best experts on this subject based on the ideXlab platform.
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Raman investigation of artificial Patinas on recent bronze protected by different azole type inhibitors in an outdoor environment
Journal of Raman Spectroscopy, 2014Co-Authors: Tadeja Kosec, Andraž Legat, Polonca RopretAbstract: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 Patinated-bronze 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 24 h. 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.
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Raman investigation of artificial Patinas on recent bronze‒part II: urban rain exposure
Journal of Raman Spectroscopy, 2012Co-Authors: Tadeja Kosec, Polonca Ropret, Andraž LegatAbstract: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 Preseren, 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.
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An electrochemical impedance study of the corrosion protection of artificially formed Patinas on recent bronze
Electrochimica Acta, 2012Co-Authors: Helena Otmačić Ćurković, Tadeja Kosec, Katarina Marušić, Andraž LegatAbstract:The Patina that covers bronze often has an aesthetic and/or historical value. It should therefore be protected from corrosion in aggressive urban environments. In the present study, two green chemically obtained bronze Patinas were examined, as well as an electrochemical Patina that resembles the natural Patina. Different protective systems were applied to the samples: azole-based inhibitors in an ethanol solution, azole-based inhibitors in polymer coating or wax coating. The efficiency of these protective systems during immersion in simulated urban rainwater was monitored by electrochemical impedance spectroscopy. The results showed that the protection of Patinated bronzes by the inhibitor/ethanol system was long-lasting and most effective for electrochemically Patinated bronze. Protective properties of investigated inhibitor/Paraloid B44 systems were found to depend on inhibitor present in the coating as well as on properties of the Patina layer on which it was applied. For all types of Patina BTA/Paraloid B44 coating exhibited better protecting properties than MTI/Paraloid B44 coating. Carnauba wax was found to provide stabile and effective protection, especially for nitrate Patinated bronze.
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Investigation of the corrosion protection of chemically and electrochemically formed Patinas on recent bronze
Electrochimica Acta, 2010Co-Authors: Tadeja Kosec, Helena Otmačić Ćurković, Andraž LegatAbstract:In humid atmospheres, copper and bronze passivate, with the formation of an oxidized layer (Patina). Patinas may also be created by chemical Patination procedures, which are frequently used to achieve special visual effects. However, unless these Patinas are effectively protected, corrosion may be initiated when they are exposed to a polluted atmosphere. In the present study the stability of the green nitrate and the green chloride type of Patinas, and of electrochemically formed Patina, was investigated, as well as suitable protection methods. Two inhibitors, dissolved in different solutions, were used: benzotriazole and the less hazardous imidazole type of inhibitor, and waxes. The dissolving of untreated and pre-treated surfaces, in test solutions representing urban rain (pH 5.0), was investigated by means of potentiodynamic techniques. The microstructure of the Patinas and the corrosion products was investigated by SEM/EDX. It was found that both investigated inhibitors inhibited the corrosion of electrochemically formed Patina, and of the green chloride type of Patina, but were ineffective in the case of the green nitrate type of Patina. The difference between the performance of the investigated inhibitors when brushed onto Patinated bronze, and when the bronze is immersed in a solution containing the dissolved inhibitor, was determined.