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Fluoride coatings on magnesium prepared in melts
Drábiková, Juliána ; Richtera, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This work deals with the corrosion protection of magnesium alloy AZ31, AZ61, AZ91 using fluoride conversion coating prepared from Na[BF4] melt. The theoretical part describes the properties of magnesium alloys, the recent results of fluoride conversion coatings preparation and analysis of the available literature about the properties of salt Na[BF4] and its decomposition products. The experimental part was devided into two main sections. The first deals with the corrosion resistance of the treated magnesium alloys (AZ31, AZ61, AZ91 and AZ91 annealed) in the Na[BF4] melt. Corrosion resistance was tested using potentiodynamic tests and tests in the corrosion chamber. In the second part, the mechanism has been studied for preparing fluoride conversion coating, where it was shown that in air-free atmosphere the oxidizing agent in the process is boron, which is reduced from BIII to B0, and thereby enables the fluoride conversion coating.
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Evaluation of electrochemical characteristics of AZ31 wrought magnesium alloy
Hána, Tomáš ; Tkacz, Jakub (referee) ; Drábiková, Juliána (advisor)
This thesis deals with the issue of electrochemical characterization of AZ31 wrought magnesium alloy, which was exposed to corrosive environment of 0.1 moldm3 solution of sodium chloride. Electrochemical impedance spectroscopy and potentiodynamic tests were used for evaluation of electrochemical characteristics such as corrosion rate, corrosion current density, corrosion potential and polarization resistance. There is a summary of ways of a production of magnesium alloys, influence of alloying element on properties of material and types of corrosion, which leads to degradation of material in the theoretical part. In the experimental part there is characterization of used methods, summary of results and a discussion of obtained data and its comparison.
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Preparation and Characterization of Fluoride Conversion Coatings on Biodegradable Magnesium Alloys
Drábiková, Juliána ; Hadzima, Branislav (referee) ; Brezinová,, Janette (referee) ; Ptáček, Petr (advisor)
The submitted work is aimed at the unconventional fluoride conversation coating preparation on the AZ31, AZ61, ZE10 and ZE41 magnesium alloys by their immersion in Na[BF4] molten salt. The influence of the preparation parameters (such as temperature and time) on the quality of the fluoride conversion coating is investigated. Methods of light and scanning electron microscopy were used for the evaluation of morphology, chemical composition and thickness of the coating. Short and long-term corrosion tests were executed to analyze the corrosion performance in simulated body fluid solution at 37 ± 2 °C with and without the fluoride conversion coating. The short-term behavior was evaluated by potentiodynamic tests, namely by the linear polarization. Long-term performance was assessed by electrochemical impedance spectroscopy or immersion tests. The coating preparation parameters influence on the character of the formed fluoride conversion coating was defined based on the obtained results. The next part of the thesis deals with the description of the possible mechanism of formation and kinetics of growth of the unconventional fluoride conversion coating on the selected AZ61 magnesium alloy. In this part, further detailed analyses were carried out to investigate the microstructure and chemical composition of the fluoride conversion coating using focused ion beam, transmission electron microscopy and X-ray photoelectron spectroscopy.
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Propsective surface treatments of magnesium alloys
Drábiková, Juliána ; Doležal, Pavel (referee) ; Zmrzlý, Martin (advisor)
The aim of this bachelor thesis is to summarize the methods of surface treatment of magnesium alloys and discussion of theireffectiveness of corrosion protection. In contrast to other metallic material used in technical practice, magnesium alloys have the lowest corrosion resistance, which can be increased by alloying or by use of surface treatments. The introduction part of the thesis deals with general knowledge about magnesium, its alloys AZ31, AZ91 and their corrosion processes. The recherché includes actual results of research about these alloys. Emphasizedare fluoride conversion coatings and composite coatings based on nickel, where their preparation is described and attention is focused on their properties in the sense of corrosion protection. Concluding the work, we give a critical assessment of the pros and cons of corrosion protective coatings on Mg alloys. Finally, there are suggested some convenient experiments to prove the repeatability of results published in the recherché literature.
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Preparation and Characterization of Fluoride Conversion Coatings on Biodegradable Magnesium Alloys
Drábiková, Juliána ; Hadzima, Branislav (referee) ; Brezinová,, Janette (referee) ; Ptáček, Petr (advisor)
The submitted work is aimed at the unconventional fluoride conversation coating preparation on the AZ31, AZ61, ZE10 and ZE41 magnesium alloys by their immersion in Na[BF4] molten salt. The influence of the preparation parameters (such as temperature and time) on the quality of the fluoride conversion coating is investigated. Methods of light and scanning electron microscopy were used for the evaluation of morphology, chemical composition and thickness of the coating. Short and long-term corrosion tests were executed to analyze the corrosion performance in simulated body fluid solution at 37 ± 2 °C with and without the fluoride conversion coating. The short-term behavior was evaluated by potentiodynamic tests, namely by the linear polarization. Long-term performance was assessed by electrochemical impedance spectroscopy or immersion tests. The coating preparation parameters influence on the character of the formed fluoride conversion coating was defined based on the obtained results. The next part of the thesis deals with the description of the possible mechanism of formation and kinetics of growth of the unconventional fluoride conversion coating on the selected AZ61 magnesium alloy. In this part, further detailed analyses were carried out to investigate the microstructure and chemical composition of the fluoride conversion coating using focused ion beam, transmission electron microscopy and X-ray photoelectron spectroscopy.
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Evaluation of electrochemical characteristics of AZ31 wrought magnesium alloy
Hána, Tomáš ; Tkacz, Jakub (referee) ; Drábiková, Juliána (advisor)
This thesis deals with the issue of electrochemical characterization of AZ31 wrought magnesium alloy, which was exposed to corrosive environment of 0.1 moldm3 solution of sodium chloride. Electrochemical impedance spectroscopy and potentiodynamic tests were used for evaluation of electrochemical characteristics such as corrosion rate, corrosion current density, corrosion potential and polarization resistance. There is a summary of ways of a production of magnesium alloys, influence of alloying element on properties of material and types of corrosion, which leads to degradation of material in the theoretical part. In the experimental part there is characterization of used methods, summary of results and a discussion of obtained data and its comparison.
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Evaluation of electrochemical properties of AZ31 magnesium alloy prepared by sqeeze casting
Mikulášová, Kristýna ; Drábiková, Juliána (referee) ; Tkacz, Jakub (advisor)
The bachelor thesis deals with electrochemical characterization of corrosion properties of magnesium alloy AZ31. This alloy produced by squeeze casting method was exposed to a corrosive environment of 0,1 M solution of NaCl. Scanning electron microscopy (SEM) with elemental analysis measured by energy dispersive spectroscopy (EDS) was used for the evaluation of the AZ31 magnesium alloy’s surface. Consequently, short term corrosion tests (5 min) were undertaken by potentiodynamic tests. Long term tests (168 h) were measured by electrochemical impedance spectroscopy (EIS). The effects of different alloy surface treatment (grinding and polishing) on the corrosion rate of the AZ31 magnesium alloy produced by squeeze casting method were evaluated by measured results.
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Fluoride coatings on magnesium prepared in melts
Drábiková, Juliána ; Richtera, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This work deals with the corrosion protection of magnesium alloy AZ31, AZ61, AZ91 using fluoride conversion coating prepared from Na[BF4] melt. The theoretical part describes the properties of magnesium alloys, the recent results of fluoride conversion coatings preparation and analysis of the available literature about the properties of salt Na[BF4] and its decomposition products. The experimental part was devided into two main sections. The first deals with the corrosion resistance of the treated magnesium alloys (AZ31, AZ61, AZ91 and AZ91 annealed) in the Na[BF4] melt. Corrosion resistance was tested using potentiodynamic tests and tests in the corrosion chamber. In the second part, the mechanism has been studied for preparing fluoride conversion coating, where it was shown that in air-free atmosphere the oxidizing agent in the process is boron, which is reduced from BIII to B0, and thereby enables the fluoride conversion coating.
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Propsective surface treatments of magnesium alloys
Drábiková, Juliána ; Doležal, Pavel (referee) ; Zmrzlý, Martin (advisor)
The aim of this bachelor thesis is to summarize the methods of surface treatment of magnesium alloys and discussion of theireffectiveness of corrosion protection. In contrast to other metallic material used in technical practice, magnesium alloys have the lowest corrosion resistance, which can be increased by alloying or by use of surface treatments. The introduction part of the thesis deals with general knowledge about magnesium, its alloys AZ31, AZ91 and their corrosion processes. The recherché includes actual results of research about these alloys. Emphasizedare fluoride conversion coatings and composite coatings based on nickel, where their preparation is described and attention is focused on their properties in the sense of corrosion protection. Concluding the work, we give a critical assessment of the pros and cons of corrosion protective coatings on Mg alloys. Finally, there are suggested some convenient experiments to prove the repeatability of results published in the recherché literature.
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