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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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Ni-P based coatings preparation on AZ61 wrought magnesium alloy after heat treatment
Otoupal, Dominik ; Tkacz, Jakub (referee) ; Kosár, Petr (advisor)
The aim of the bachelor’s thesis is preparation of heat treated wrought magnesium alloy AZ61 and exclusion nickel-phosphorus coating using electroless deposition to the original and heat treated magnesium alloy AZ61. The theoretical part contains two main chapters. The first chapter describes the alloy AZ61. The second part deals with electroless deposition of nickel-phosphorus coating. At the conclusion of the theoretical part is searches on the topic. Experimental part deals with characterization and description of the magnesium alloy, its heat treatment and electroless plating. They were studied chemical and mechanical properties of the original and heat treated AZ61 and nickel-phosphor coating. For the study methods of scanning electron microscopy with energy-dispersive spectroscopy, optical light microscope and Vickers’s microhardness was used.
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Evaluation of electrochemical properties of wrought Mg-Al-Zn type magnesium alloys
Slouková, Karolína ; Hadzima, Branislav (referee) ; Tkacz, Jakub (advisor)
The aim of this master’s thesis is electrochemical characteristics evaluation of magnesium alloys. The theoretical part describes the properties of magnesium and its alloys and their corrosion characteristics. In the experimental part are presented results of corrosion resistance measurement of two types of wrought magnesium alloys. It was AZ31 and AZ61 magnesium alloys, which were measured in Hank’s solutions with addition of ions Ca2+ and Mg2+ (SBF+) and without addition of the ions (SBF). The solution temperature during the measurement was 37 ± 1 °C. The experiments were used electrochemical impedance spectroscopy (EIS) and potentiodynamic tests using linear polarization (LP). EIS measurements were done in times of 5 minutes, 1, 2, 4, 8, 12, 24, 48, 72, 96 and 168 hours. Potentiodynamic tests were only short-term and they started after 5 minutes of stabilization. Both methods were used for measuring the electrochemical characteristics of polished and ground surface of the samples. The most important measurement results were polarization resistance, corrosion potential and corrosion current density. The electrochemical measurements are used to estimate the chemical composition influence and alloy’s structure of the corrosion resistance.
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Corrosion Resistance of Structural Magnesium Alloys
Tkacz, Jakub ; Pacal, Bohumil (referee) ; Hadzima, Branislav (referee) ; Havlica, Jaromír (advisor)
This thesis describes magnesium alloys, their properties and methods of their production. However, experimental part is focused on AZ91 magnesium alloy. Conversion coatings were prepared on the AZ91 surface – chromate coating, phosphate permanganate coating and fluoride coating. Corrosion resistance of the prepared coatings were compared by immersion tests and by potentiodynamic methods. Evaluation of corrosion resistance by immersion tests was successful only for phosphate permanganate coating. Only this coating was removed during cleaning of the samples. For comparison of corrosion resistance was important to find the correct procedures and optimize the measurements methods. For these purposes have been chosen galvanic zinc coating on steel sheets. Thickness of the zinc coating were 8 and 30 microns. This coatings provide uniform zinc surface without heterogenities which was important for the potentiodynamic measurements. After optimization methods for potentiodynamic measurements by galvanic zinc coatings have been measured magnesium alloy AZ91 uncoated and coated by conversion coatings. For uncoated AZ91 magnesium alloy was determined suitable method so called virgin cathodic curve. On the other hand, for the coated AZ91 magnesium alloys was determined suitable method so called combined curve, within which we measured cyclic voltammetry curve (± 5 mV) and then virgin anodic curve.
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Electrochemical characteristics of AZ31 and AZ61 magnesium alloys in Hanks‘ solutions
Minda, Jozef ; Wasserbauer, Jaromír (referee) ; Tkacz, Jakub (advisor)
This thesis deals with the characterization of electrochemical corrosion properties of magnesium alloys as promising materials for biomedical applications. The wrought alloys AZ31 and AZ61 were used and exposed to corrosive environments of Hanks solutions (SBF) to simulate environmental conditions in living organisms. For the evaluation of the surfaces was used scanning electron microscopy (SEM) with elemental analysis measured by energy-dispersive spectroscopy (EDS). Short-term (5 min) and long-term (72 h) corrosion tests were conducted in order to optimize the measurement methodology and obtain corrosion parameters - especially corrosion potential (Ekor), corrosion current density (ikor) and polarisation resistance (RP). To evaluation of the short-term tests were by potentiodynamic tests, namely the linear polarization (LP) test. Long-term tests were measured by electrochemical impedance spectroscopy (EIS). Effects of the composition of the alloys (AZ31 and AZ61), surface treatment (grinding and polishing) and the composition of the solution (SBF without Ca, Mg, and with Ca, Mg) were compared. Complex corrosion behaviour in time was characterized and corrosion mechanisms were discussed.
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Reactivity and controll of properties of metallic materials
Tkacz, Jakub ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
This thesis is focused on corrosion protection of magnesium alloys AZ 91. Very important is material corrosion in some environments and last but not least surface treatment as grinding, polishing and etching. Theoretical part of this thesis is about magnesium and magnesium alloy. It focuses on properties, in order to determine the best procedure for corrosion protection. It characterize material corrosion- for example corrosion in special environment (atmosphere, water, etc.) or elektrolyte corrosion. Big part of theoretical part is focused on electrochemistry, in particular kinetic aspects (Tafel diagrams, corrosion current, etc.) and potentiostatic testing, where are observed properties of material in relation to potential: corrosion potential Ecorr, brakedown potential Ebd and repassivation potential Erp. This work present preparing, utilization and positive or negative aspects of corrosion protection. Metallography is important too since metallographical preparation is crucial for the research on the material. Described metallography procedures are mounting, grinding, polishing, etching and interpretation. Experimental part of this thesis is in particular about corrosion properties of magnesium alloy AZ 91. It focuses on calculation of corrosion rate in defferent environments. Principle is mass defekt of the alloy. The environments are: destilled water, hot service water and 3% NaCl solution (like sea water). Last but not least are important. procedure manipulation with materials. Very important are choice and composition of solutions, etching time, choice of polishing cloth, lubricant solution and good pressure. Beacuse of this aspects can be show corrosion action of environments on magnesium alloy AZ 91 by photographies.
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Influence of fly ash containing products after flue gases denitrification to corrosion of metal parts of technological units
Řezanina, Marek ; Tkacz, Jakub (referee) ; Opravil, Tomáš (advisor)
This thesis deals with the influence of fly ash containing residues of flue gas denitrification after SNCR method. There are remains of ammonium compounds and bicarbonate compoudns, especially the hydrogen ammonium sulphate in solid combustion products, when using the SNCR method. This substance itself is corrosive, and it releases ammonium ions to the solution and releases an ammonia gas in case the pH is higher than 9. Because the fly ash gets processed, transported, and if you add lime it also produces the so called stabilizate. it is necessary to think about the corrosion of equipment in which these processes take place. The aim of this thesis is to assess the degree of corrosion of various types of steel in corrosive environments described above.
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Nickel coatings and their properties
Buchtík, Martin ; Tkacz, Jakub (referee) ; Zmrzlý, Martin (advisor)
The aim of the bachelor’s thesis was summary of existing knowledge concerning to electroless deposition of nickel coatings and their properties. In the theoretical part there are two chapters. In the first chapter present knowledge of chemical nickel plating is described in details. It also discuss mechanisms of this type of coating and individual components of nickel plating bath. In the second chapter there is summarized knowledge of composite coatings deposition and description of their mechanical properties. The experimental part deals with deposition of composite coatings on steel substrates and heat treatment of Ni-P coatings. Dependence of microhardness on temperature of heat treatment was studied and then there is also described dependence of microhardness on duration of heat treatment. Deposited coatings, their morphology and composition were studied using scanning electron microscope and EDS analysis. The values of microhardness of both types of coatings were measured and compared using microhardness tester.
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