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Preparation of yttrium-based coating to increase the corrosion resistance of AZ31 magnesium alloy
Kolařík, Václav ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The subject of the bachelor thesis was the preparation and characterization (morphological and chemical) of coatings based on layered double hydroxides (LDH) with yttrium on AZ31 magnesium alloy to improve the corrosion resistance of the alloy. The coatings were prepared under mild and hydrothermal conditions and the synthesis was supported by thermodynamic assumptions. The corrosion resistance of the AZ31 alloy with coatings was described by potentiodynamic measurements and compared with the pure AZ31 alloy. This was followed by a description of the morphological and elemental composition through SEM-EDS analysis, and confirmation of the formation of the structures observed by this method was performed through FTIR analysis. The best coating prepared under mild conditions was a sample prepared at 90 °C for 24 h with a yttrium concentration of 0,05 M and under hydrothermal conditions it was a coating prepared at 120 °C for 30 h with a yttrium concentration of 0,075 M. SEM-EDS and FTIR analysis did not show the formation of MgY-LDH but the formation of Mg(OH)2. Yttrium was minorly represented in the coatings where it could be present, e.g. as Y(OH)3. Yttrium was shown to have a positive effect on the preparation of the coatings compared to the sample prepared without yttrium under the same reaction conditions.
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Preparation and characterization of magnesium hydroxide on the surface of AZ31 magnesium alloy depending on the hydroxide cation used
Bejček, Martin ; Hasoňová, Michaela (referee) ; Doskočil, Leoš (advisor)
The bachelor thesis deals with the preparation and characterization of magnesium hydroxide on the surface of AZ31 alloy depending on the hydroxide cation used. The theoretical part focuses on magnesium and also on its alloys. Furthermore, corrosion in aqueous and chloride environments is discussed. The last chapter of the theoretical part focuses on the formation and preparation of magnesium hydroxide on magnesium alloys. The experimental part describes the actual hydrothermal synthesis of protective coatings on AZ31 magnesium alloy as well as the different methods used during the study. A temperature of 120 °C and different synthesis times (2h, 4h, 8h, 12h and 24h) were chosen as preparation conditions. The methods used included SEM-EDS analysis to document the surface and coating thickness of the material. This was followed by a potentiodynamic polarization method to determine the corrosion resistance of the prepared samples in a 0.15M NaCl. The last analysis was FTIR spectrometry, which served to determine the compounds that made up the protective coating. The results showed that the cations of the hydroxides used did not affect the morphology or the amount of prepared magnesium hydroxide on AZ31 alloy. The resulting coatings were characterized by good corrosion resistance compared to the reference AZ31 alloy. The best results were obtained for 24h samples. The thickness of the coatings reached 10 m at 120 °C and at a hydrothermal synthesis time of 24 h.
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Preparation and characterization of fluoride conversion coating on magnesium material
Šmíd, Jakub ; Doskočil, Leoš (referee) ; Březina, Matěj (advisor)
This thesis deals with the preparation of fluoride conversion coating on magnesium material. The effect of the coating time on the formation of the coating was investigated and the corrosion resistance of the resulting coatings was measured. The theoretical part is focused on magnesium and its alloys, powder metallurgy, corrosion and protection against it. Furthermore, conversion coatings, especially fluoride coatings, and their applications are discussed. The review section focuses on the current state of research in the field of fluoride conversion coatings. The experimental part describes the procedures of sample preparation and coating formation. The effect of time on the formation of the coating is investigated by monitoring the microstructure, mainly by elemental analysis of the surface of the samples in the section. Furthermore, the corrosion resistance of the samples is measured by potentiodynamic polarization in NaCl solution.
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Use of acoustic emission technology to assess corrosion of materials
Procházka, Adam ; Vašíková, Simona (referee) ; Binar, Tomáš (advisor)
The thesis deals with the description of acoustic emission as a non-destructive testing method and its use in the detection of material corrosion. The first part describes the theoretical principles dealing with the explanation of what acoustic emission is, how it is defined according to the standard, what are the types of acoustic emission and how it is tested. It then discusses corrosion, the types of corrosive environments where corrosion occurs and the types of corrosion tests. It also describes where acoustic emission has been used in practice and what experiments it has been used for in terms of material monitoring. The next part of the paper describes the experiment of acoustic emission measurement on grey cast iron samples, describes the fabrication of the samples, the use of corrosion protectors, and the placement of the samples in a condensation chamber for continuous testing. The last part is the evaluation of the results .
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Assessment of corrosion degradation in materials
Plichta, Lukáš ; Zimáková, Jana (referee) ; Binar, Tomáš (advisor)
The work describes the principle of degradation of corrosion in materials, specifically metals and their alloys. Corrosion is divided into several aspects. The fundamental division according to its origin divides this phenomenon into chemical, electrochemical and biological corrosion., It distinguishes between uniform, non-uniform, spot, selective, crevice, erosive, intercrystal corosion and corrosion cracking according to corrosion damage. It also presents corrosion testing options. In the experimental part, it describes the production of samples from gray cast iron, their dimensions, applied surface protection, hardness measurement and roughness measurement. This work also conducts electrochemical tests and tests in a condensation chamber on selected samples of gray cast iron GJL-250MnCuCr.
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Využití zinkových povlaků pro antikorozní ochranu ocelových součástí
Straka, Dominik
This Bachelor thesis „Use of zinc coats for anticorrosive protection of steel components“ characterizes corrosion and its effect on steel materials when being in a corrosive environment. Moreover, it categorizes corrosion and defines various methods of how steel materials can be protected against it. Special focus is given to protection using metal coats with lower electrode potential than Fe. Furthermore, this thesis determines particular methods of how to create metal coats depending on the type of material. Especially, the use of zinc applied by the hot-dipped and galvanic method is discussed. Quick laboratory tests are identified as a suitable method in order to evaluate the quality and resistance of created coats. Finally, lifespan and corrosive resistance of each coat are assessed considering the environment in which these coats are exposed.
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Methodology for the classification of corrosion aggressiveness of internal environments contaminated with volatile organic acids
Kouřil, M. ; Boháčková, T. ; Švadlena, J. ; Prošek, T. ; Strachotová, K. Ch. ; Kreislová, K. ; Fialová, P. ; Majtás, Dušan
The aim of the methodology is to specify the procedures for determining the corrosion aggressiveness of internal atmospheres for the area of historic preservation, especially in objects with an increased risk of volatile occurrence\norganic substances, which can endanger metal and other objects with their corrosive aggressiveness cultural and historical value. Target locations are, for example, archives, libraries, exhibition spaces and depositories of museums and churches and target objects of lead seals, organ pipes containing lead, stained glass windows, tin-lead dishes, technical monuments with lead solders, printing letters, etc.
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ELECTROCHEMICAL CHARACTERISTICS OF ADVANCED MAGNESIUM ALLOYS PROCESSED BY POWDER METALURGY
Minda, Jozef ; Nový, František (referee) ; Stoulil, Jan (referee) ; Hadzima,, Branislav (advisor)
The subject of the present dissertation is basic research in the field of advanced magnesium-based materials with high potential for medical applications prepared by powder metallurgy. These materials are evaluated in terms of corrosion behaviour in corrosive media by chemical composition and set conditions simulating the physiological environment of the human body (Hank's Balanced Salt Solution was used in this work). The aim is to analyze the influence of the processing parameters, chemical composition and structure on electrochemic characteristics of theprepared materials. For this purpose, a deeper of the the corrosion behavior, to obtain electrochemical characteristics and to investigate the degradation properties of the studied materials by means of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), with elemental analysis by energy-dispersive spectroscopy (EDS) and other complementary methods. The materials for the experiments are prepared using powder metallurgy, which allows the formation of composites with compositions that do not match conventional manufacturing technologies. Thus, pure Mg samples were prepared at process parameters with pressing pressures of 100 and 500 MPa at 400 °C and also samples pressed at 500 MPa and room temperature were tested. Furthermore, MgZn composites prepared at a pressing pressure of 500 MPa and a temperature of 300 °C with a Zn content of 1, 5, 10 and 15 wt.% or MgZn composites pressed at a pressure of 500 MPa and a temperature of 400 °C with a Zn content of 1, 5 and 10 wt.%. Composites of the Mg-hydroxyapatite binary system pressed at 500 MPa and 400 °C with hydroxyapatite contents of 10, 20, 30 and 40 wt.% were also studied. The degradation mechanisms of these materials were investigated using the above mentioned methods and the basic electrochemical parameters and their evolution during the time of exposure were determined. From the results, the influence of process parameters, chemical composition and the corrosive environment itself on the studied materials is evaluated. Several materials that appear to be most suitable for the medical application are described and the causes of degradation behaviour at the level of the structure of the materials and their electrochemical interaction with the corrosive environment are also discussed in the dissertation thesis. Compaction and densification positively influenced pure Mg samples, where samples pressed at 500 MPa and 400 °C are further selected as reference material. Increasing Zn content positively electrochemically affects the corrosion resistance of MgZn series of samples pressed at 500 MPa and 300 °C, on the contrary, in the combination of electrochemical - microgalvanic and structural effects, low Zn content is optimal for MgZn composites pressed at 500 MPa and 400 °C. For Mg-hydroxyapatite materials, in agreement with the literature, it was shown that the most stable corrosion product layers with the best corrosion properties and evolution in time are formed for samples with hydroxyapatite content up to 10 wt.%.
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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.
Fulltext:  PDF; PDF
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Measurement of corrosion resistance of the material
ŠVARCOVÁ, Denisa
Aim of the bachelor thesis is bringing the concept of corrosion closer to second grade pupils of elementary school. In the theoretical part of the work is summary of the concept of corrosion, types of corrosion and protection against corrosion. In the practical part is performed measurement of corrosion resistance of martensitic steel depending on temperature and time. The didactic part of the work consists of laboratory exercises, where the pupils try to measure the corrosion resistance of the material in different environments, and of worksheet, which is used to repetition and to complete of the concept corrosion.
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