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Metodika klasifikace korozní agresivity vnitřních prostředí znečištěných těkavými organickými kyselinami
Kouřil, M. ; Boháčková, T. ; Švadlena, J. ; Prošek, T. ; Strachotová, K. Ch. ; Kreislová, K. ; Fialová, P. ; Majtás, Dušan
Cílem metodiky je konkretizovat postupy určení korozní agresivity vnitřních atmosfér pro oblast památkové péče, zejména v objektech se zvýšeným rizikem výskytu těkavých organických látek, které mohou svou korozní agresivitou ohrožovat kovové i další objekty s kulturní a historickou hodnotou. Cílovými lokalitami tedy jsou například archivy, knihovny, výstavní prostory a depozitáře muzeí a kostely a cílovými předměty olověné pečetě, varhanní píšťaly obsahující olovo, vitráže, cínoolověné nádobí, technické památky s olověnými pájkami, liteřina, apod.
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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
Korozní napadení kovových historických artefaktů těkavými organickými sloučeninami (VOA – volatile organic acids) je běžné ve vnitřních atmosférách, v nichž se nacházejí zdroje VOA a kde nejsou přijímána dostatečná opatření pro eliminaci agresivního působení těchto látek na kovy. Postup pro stanovení korozní agresivity vnitřních atmosfér vůči kovům definují tři části normy ČSN EN ISO 11844 „Koroze kovů a slitin - Klasifikace vnitřních atmosfér s nízkou korozní agresivitou“. Třídy korozní agresivity (IC1 až IC5) jsou založeny mimo jiné na určení hmotnostního úbytku korozních kupónů ze stříbra, mědi, oceli, zinku a olovo. Olovo bylo do první části normy ČSN EN ISO 11844-1 zařazeno v roce 2021 na základě výsledků projektu NAKI II „Metodika klasifikace korozní agresivity vnitřních prostředí pro sbírkové předměty ze slitin olova“ (DG18P02OVV050), jakožto kov specificky citlivý na přítomnost těkavých organických kyselin. Cílem metodiky je konkretizovat postupy určení korozní agresivity vnitřních atmosfér pro oblast památkové péče, zejména v objektech se zvýšeným rizikem výskytu těkavých organických látek, které mohou svou korozní agresivitou ohrožovat kovové památky. Cílovými lokalitami tedy jsou například archivy, knihovny, výstavní prostory a depozitáře muzeí a kostely a cílovými předměty olověné pečetě, varhanní píšťaly obsahující olovo, vitráže, cínoolověné nádobí apod. Zdrojem těkavých organických kyselin je celá řada materiálů tvořících běžné vybavení v daných vnitřních prostředích – dřevěné obložení a stropy, nábytek, skříně, vitríny, ale i další vystavované nebo uložené předměty.
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Optical evaluation of corrosion products using colorimetric spectroscopy
Majtás, Dušan ; Fialová, P.
Aim of this work is to test possibility to utilize colorimetric spectroscopy for monitoring the corrosion of lead and tin-lead alloys. And furthermore method suitability for preliminary corrosion evaluation of cultural heritage objects. According to literature colorimetry is used to monitor patinas of bronze objects, thus the method might be also suitable for lead based alloys. Samples used were made from commercially produced lead plate. These were exposed in the climatic chamber to different relative humidity (60, 80, 90 %). After the exposure the corrosion products with different color formed on sample surface. These corrosion products were evaluated by different methods: optical microscopy, colorimetric spectroscopy, and X-ray chemical analysis. Collected colorimetric data display difference between treatments suitable for patina evolution monitoring. The paper presents obtained results and comparison of applied methods.
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Corrosion products phase identification using micro-Raman and FTIR
Majtás, Dušan ; Mácová, Petra
Phase identification of corroded metal objects might be problematic because corrosion products are usually a complex mixture of different phases. Furthermore, some of present phases may be either semi-crystalline or amorphous. The most suitable procedure is to use X-ray diffraction (XRD), for identification of crystalline phases in bulk, in combination with micro-Raman spectroscopy to obtain information on smaller scale and given location. Micro-Raman spectroscopy identifies crystalline and semi-crystalline phases. The literature also reports of the application of Mössbauer spectroscopy to identify amorphous phases. In this work, the combined use of Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy is evaluated. The methods may be interchangeable to some point. But is it safe to assume that all phases present can be detected?
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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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Cracking of ferritic stainless steel tubes during production process
Majtás, Dušan ; Kreislová, K. ; Viani, Alberto ; Pérez-Estébanez, Marta ; Geiplová, H.
From the economic reasons many products originally made from austenite stainless steel are nowadays made from ferritic stainless steel. Ferritic steels have relatively low yield strength and the work hardening is limited. They cannot be hardened by heat treatment and only moderately hardened by cold working. Commercially made stainless steel tubes from ferritic steel, used for industrial plumbing was examined on presence of cracks. The cracking was present on the inner side of the convoluted tube shape. The tube manufacturing process consisted of continual bending of the sheet to tube shape, weld the tube, then of cold shaping by pulling through rib-forming frames, which is done in several steps. Then thermal treatment applies to the nearly finished product to remove stress remaining in the structure. Prime suspect was deformation beyond the ductility of used material. However the stress-strain tensile testing does not approved this hypothesis. Several samples of failed material were taken together with reference, and were examined by optical microscopy, and X-Ray Diffraction structure analysis. The structure of the cracked tubes does not show the signs of deformation over the limit, except the location near to the crack itself. Interestingly enough the failed material showed more homogenous structure than the original one. Needle like structures were found when the material is “overetched”, on these structures concentration of stress under bending occur. This structure was identified as δ-ferrite, however its presence in α-ferrite matrix is unclear.
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