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Metodika klasifikace korozní agresivity vnitřních prostředí znečištěných těkavými organickými kyselinami
Kouřil, Milan ; Boháčková, Tereza ; Švadlena, Jan ; Prošek, Tomáš ; Strachotová, Kristýna Charlotte ; Kreislová, Kateřina ; Fialová, Pavlína ; Majtás, Dušan
Corrosion of metal historical artefacts by volatile organic acids (VOA) is common in indoor atmospheres where VOA sources are present and where insufficient measures are taken to eliminate the aggressive effects of these substances on metals. The procedure for determining the corrosion aggressiveness of indoor atmospheres towards metals is defined in three parts of the standard EN ISO 11844 'Corrosion of metals and alloys - Classification of indoor atmospheres with low corrosion aggressivity'. The corrosion aggressivity classes (IC1 to IC5) are based, among others, on the determination of the mass loss of corrosion coupons of silver, copper, steel, zinc and lead. Lead was included in the first part of EN ISO 11844-1 in 2021, based on the results of the NAKI II project "Methodology for the classification of corrosion aggressiveness of indoor environments for lead alloy collectors" (DG18P02OVV050), as a metal specifically sensitive to the presence of volatile organic acids. The aim of the methodology is to specify the procedures for determining the corrosion aggressivity of indoor atmospheres for the field of conservation, especially in objects with a higher risk of the presence of volatile organic compounds, which can threaten metallic monuments by their corrosion aggressivity. Thus, target locations are, for example, archives, libraries, exhibition spaces and depositories of museums and churches, and target objects are lead seals, organ pipes containing lead, stained glass, pewter utensils, etc. The sources of VOCs include a range of materials that make up common furnishings in indoor environments - wood paneling and ceilings, furniture, cabinets, display cases, as well as other items on display or stored.
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Iron alloys outdoor corrosion and laboratory simulation - comparison
Majtás, Dušan ; Mácová, Petra ; Kreislová, Kateřina ; Příhoda, J.
Simulation of iron alloy corrosion is widespread used to predict corrosion resistance. The simulation using corrosion chambers or climatic chambers provides reasonable information on corrosion resistance, the corrosion rate however must be compared to real exposition as the corrosion in simulated environment is accelerated compared to real situation. However the composition of corrosion products and its structure is different question. The corrosion products composition is dependent on corrosion process. The phases present are most likely the same, most voluminous hydrated oxides and oxy-hydroxides on the outside where the less voluminous oxides are present in the lower layers. However this macroscopic phase structure may not fully describe the layered structure of corrosion products, thickness of corrosion products or mechanical properties. In the vicinity of crack in corrosion products the structure is more likely to be similar to the structure near the surface.
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Cross-section analysis and mapping using Raman spectroscopy
Majtás, Dušan ; Mácová, Petra ; Kreislová, Kateřina
When dealing with corroded objects, it is necessary to identify the corrosion products to develop a proper treatment for this particular object. Using X-ray diffraction is still suitable to do the phase composition analysis of the material; however it does the analysis of the material in bulk. It is also possible to use SEM to analyze the structure of the corrosion layers on a cross-section by EBSD method; however this method is time consuming. It is more suitable to use Raman spectroscopy when studying the structure of corrosion layers. Using proper equipment, such as Raman microscope it is possible to do not only analysis of precisely given point, but it is also possible to do mapping (both 1D and 2D) of the cross-section. Taking map of surface also does need time, but is definitely less time consuming compared to EBSD method.
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