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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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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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Preparation and evaluation of fluoride conversion coating created on AZ31 wrought magnesium alloy
Matějka, Lukáš ; Wasserbauer, Jaromír (referee) ; Fintová, Stanislava (advisor)
The aim of this work is optimization of preparation parameters of fluoride conversion coating on the wrought magnesium alloy AZ31 in Na[BF4] melt. The monitored factors for determining quality of the prepared coatings are homogeneity of the coating surface on ground and polished samples of magnesium alloy, mechanical properties of the coating (adhesion and hardness) and the coating thickness. The main parameter was the change in these properties at different exposition times of the material to the salt melt. Coating surfaces were documented on an inverted light microscope with the addition of images representative samples using SEM. The coating thickness was documented with inverted light microscope using a polarization filter. The chemical composition was determined on three representative samples using an energy-dispersive X-ray spectrometer. The mechanical properties of the coatings were determined by scratch test on REVETEST Scratch Testing System with detector of acoustic emissions. The resulting scratches were documented on a light microscope. It was proved that polished samples exhibit superior coating in respect with ground samples, wherein the coating did not fill the trench after the finish treatment (grinding). Constant chemical composition has been demonstrated in all the coatings. Polished sample after 2 hours of exposure in the Na [BF 4] melt exhibits best mechanical properties. The obtained data are of practical importance in the use of the alloy AZ31 in various fields of industry, medicine and other research.
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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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Preparation and evaluation of fluoride conversion coating created on AZ31 wrought magnesium alloy
Matějka, Lukáš ; Wasserbauer, Jaromír (referee) ; Fintová, Stanislava (advisor)
The aim of this work is optimization of preparation parameters of fluoride conversion coating on the wrought magnesium alloy AZ31 in Na[BF4] melt. The monitored factors for determining quality of the prepared coatings are homogeneity of the coating surface on ground and polished samples of magnesium alloy, mechanical properties of the coating (adhesion and hardness) and the coating thickness. The main parameter was the change in these properties at different exposition times of the material to the salt melt. Coating surfaces were documented on an inverted light microscope with the addition of images representative samples using SEM. The coating thickness was documented with inverted light microscope using a polarization filter. The chemical composition was determined on three representative samples using an energy-dispersive X-ray spectrometer. The mechanical properties of the coatings were determined by scratch test on REVETEST Scratch Testing System with detector of acoustic emissions. The resulting scratches were documented on a light microscope. It was proved that polished samples exhibit superior coating in respect with ground samples, wherein the coating did not fill the trench after the finish treatment (grinding). Constant chemical composition has been demonstrated in all the coatings. Polished sample after 2 hours of exposure in the Na [BF 4] melt exhibits best mechanical properties. The obtained data are of practical importance in the use of the alloy AZ31 in various fields of industry, medicine and other research.
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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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