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Origin, composition and stability of copper pigments in wall paintings
Švarcová, Silvie ; Bezdička, Petr ; Hradil, David
Blue and green copper pigments occur in a wide range of chemically close, although mineralogically different species, which makes their proper identification nontrivial. Furthermore, they can be of various origins – natural, artificial or formed as a result of corrosion of another copper pigment. The degradation of copper pigments is a serious problem in case of artworks exposed to corrosive environment, such as wall paintings or exterior stone polychromes. In this paper, we document the variability of copper pigments used in history on examples of selected wall paintings. The problem of origin and stability of copper pigments in wall paintings is solved using advanced microanalytical investigation of paint layers together with the laboratory experiments. Microanalytical features documenting natural or artificial origin of copper pigments as well as their secondary changes caused by corrosive environment are shown and discussed.
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Corrosion damage evaluation by acoustic emission monitoring and nonlinear elastic wave spectroscopy testing
Kober, Jan ; Převorovský, Zdeněk
The development of local corrosion damage can lead to serious malfunctions and even to irreparable damage to whole structural parts. A reliable operation of a structure has to be secured, if a failure can cause health hazards and significant economic losses, i.e. in power, chemical and aerospace industry. This work is dealing with the application of acoustic emission method and a NEWS method for detection and monitoring of corrosion damage growth. The acoustic emission was recorded in situ during corrosion process. The measurement by NWMS method was performed in between corrosion tests. It was observed that the current dynamics of a corrosion process was determined by AE and that the amount of corrosion damage was corresponding to the nonlinear parameters obtained by NWMS. Both methods have already been used for fatigue damage evaluation therefore they form a universal system for non-destructive structural inspection.
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Corrosion of Nickel Exposed to LiF-NaF Molten Salt
Král, Lubomír ; Čermák, Jiří ; Matal, O. ; Šimo, T. ; Nesvadba, L.
This work is devoted to study of changes of structure and chemical composition in corrosion areas of the chosen candidate alloy, Nickel 201, for components of a LS-VHTR. The material was annealed at 1013K/10h/vacuum and at 1000°C/24h/Ar before corrosion tests. The annealed material was studied after its exposure to the molten mixture of 60 mol. % LiF + 40 mol. % NaF at the temperature of 1013K. The exposition was carried out in a quasidynamic regime, which simulates real circulation of the coolant (a mixture of molten salts) in the piping. The structure of the alloy was studied by SEM. Severe corrosion damage was observed in grain boundaries.
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Control of intergranular oxidation by thermal treatment
Rothová, Věra ; Buršík, Jiří ; Svoboda, Milan
The effect of pre-annealing at 800 °C in argon atmosphere on high temperature corrosion at 1050 °C in air was studied on two high purity nickel grades and compared to a commercial purity nickel. Moreover, the influence of fabrication was analyzed in the case of cast and cold-rolled Puratronic® nickel samples. The mutual grain orientation was measured by means of electron backscatter diffraction and grain boundaries were characterized in terms of the coincidence site lattice model. The scanning electron microscope characterization of cross sections of all the oxidized samples has been performed and compared with the literature. The influence of purity and fabrication on the high temperature oxygen ingress in nickel was discussed in terms of grain boundary character distribution.
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Corrosion of chosen Ni-based material exposed to LiF-NaF molten salts
Král, Lubomír ; Čermák, Jiří ; Matal, O. ; Šimo, T. ; Nesvadba, L.
This work is devoted to study of changes of structure and chemical composition in the surface layer of chosen candidate alloy Ni – 6 W – 9 Mo – 1.7 Ti – 7 Cr (in wt. %) for components of a LS-VHTR. The material was studied after its exposure to molten mixture 60 mol. % LiF + 40 mol. % NaF at temperature 993 and 1013K. The exposition was carried out in a quasidynamic regime, which simulates coolant (the mixture of salts) natural circulation conditions in components. The structure of the alloy was studied by SEM. Severe corrosion damage was observed in the surface layer, which thickness was about 300 μm.
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Analýza přerozdělení prvků feritických ocelí s Ni povlakem pro technologie roztavených solí
Král, Lubomír ; Čermák, Jiří ; Matal, O. ; Šimo, T. ; Nesvadba, L. ; Jílek, M.
Changes in structure and chemical composition of Ni-coated ferritic steel ČSN 411523 are studied in the present paper. The Ni-coated material is perspective for applications in molten salts technologies. The samples were subjected to corrosion in molten mixture 60 mol. % LiF + 40 mol. % NaF at temperature 953 K, the duration exposition was 100, 300 and 1000 h. Experiments were carried out in a quasidynamic regime simulating the flow of the cooling media (the mixture of molten salts) in the pipeline system. The change of chemical composition in the vicinity of interface between the Ni layer and steel substrate was measured by SEM.
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