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Preparation and characterization of thin barrier layers
Blahová, Lucie ; Mráček, Aleš (referee) ; Buršíková, Vilma (referee) ; Krčma, František (advisor)
Combinations of different acrylic resins and microcrystalline waxes are most often used for the conservation and preservation of metallic archaeological artefacts these days. However, their properties are not sufficient and satisfactory in many ways. Therefore, the aim of this doctoral thesis is to develop a conservation system which will draw on the new knowledge gained in the field of advanced materials and technologies during last years. A conservation coating based on a thin barrier film appears the most promising. The conservation coating must fulfil particularly following rather contradictory requirements: good barrier function against oxygen, humidity and other corrosive agents; transparency because of colour appearance preservation; long term stability and easy removability; possibility to apply to more objects at the same time and reasonable financial requirements of a deposition process. Parylene C polymer was chosen as suitable material for this purpose. It was prepared via modified chemical vapour deposition. Parylene removability was ensured through the soluble interlayer made of Laksil silicone-acrylic lacquer which was applied between the protected metallic object and the parylene thin film. Initially, the deposition process of Laksil/parylene bilayer was optimized, then its physical and chemical characteristics were determined and eventually, they were compared with the conventional conservation coating composed of Paraloid B72 acrylic resin and Revax microcrystalline wax. Regarding to the demands of the conservation coating, we were interested especially in barrier properties, optical properties, surface morphology and removability of Laksil/parylene bilayer. The most useful method for description of coating barrier properties was corrosion testing in which coated metallic samples were exposed to highly corrosive environment of salt spray (made of 50 g•l–1 brine), 100% humidity and temperature of 35 °C (ISO 9227). The Laksil/parylene bilayer showed excellent barrier properties; samples treated this way sustained unchanged in the corrosion chamber for almost three months. The surface roughness measured by profilometry and surface morphology scanned by SEM illustrated the synergy between Laksil and parylene layer which leads to the exceptional barrier and anticorrosion function of bilayer. The Laksil layer is able to flatten out rough surface of a substrate. Furthermore, it can toughen the item surface which is, in case of a number of archaeological findings, created by corrosion product layers with variable mechanical strength. Thereon deposited parylene film becomes smooth and defect free and can act as a good diffusion barrier. The colouristic measurements confirmed that the Laksil/parylene bilayer does not almost change the appearance of protected item, in terms of colour. The caused colour difference (ISO 11664-4) ranged around 1 which value is defined as “perceivable only for experienced observers”. The Laksil/parylene bilayer is removable thanks to the Laksil solubility in xylene. It is necessary to carefully scratch the outer parylene film to enable access of xylene solvent to the lacquer. The successful removal of Laksil/parylene bilayer was first confirmed by the EDX on metallic iron samples. Afterwards, the possibility of bilayer complete removal even from a corroded surface of the original artefact was proved by TGA. Thus the conservation treatment can be considered fully reversible.
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Electrophoresis coating
Holčapek, Jiří ; Kubíček, Jaroslav (referee) ; Žák, Ladislav (advisor)
This bachelor is based on a study of electrophoresis coating and corosion. The first part contains information about corrosion of metal and the importance of protecting metal parts. Then it deals with the technology of electrophoresis coating and technological process of creating electrophoresis coating. Finally, new trends in the field of electrophoresis coating are presented.
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Povrchové úpravy kovů pomocí práškového lakování
Čermák, David
The bachelor's thesis deals with powder coating and pretreatment of the surface of steel products. In the beginning of the thesis, information is given about current methods of anti-corrosion protection of metals. Equipped with a description of the mechanical pretreatment of metals before powder coating corrosion protection. This chapter is followed by chemical preparation. The types of application of powder coatings and the associated advantages and disadvantages are further described in more detail. The next chapter is the lines of powder coating plants, in which the transport processes necessary for technological feasibility are described. At the end, issues related to the ecological and economic aspects accompanying the powder coating technology are analyzed. This chapter also includes safety risks and possible negative impacts on nature.
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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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Zpracování ocelových plechů pomocí počítačem řízených strojů
Tichý, Michal
This bachelor thesis is focused on computer-controlled machines, which process steel sheets of tin while using the method of forming. The thesis is divided into three sections. The first section summarizes the production process of steel sheets focusing on different types of steel. Next section deals with the description of forming machines which form the steel sheets. The primary point of this section is to describe the machines that produce mouldings and burnouts. Third section deals with the temporary anticorrosive protection during the process of stocking and transportation of finished goods.
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Antikorozní ochrana ocelových součástí pomocí kovových povlaků
Vyškovský, Josef
This work focuses on evaluation of mechanical and anticorrosive properties of zinc coatings. Work as a first characterizes kind of corrosion and possibilities of corrosion protection measures. For the purpose of the experiment, test samples representing a cross-section of current methods of corrosion protection using zinc coatings were prepared. Mechanical properties were evaluated by bend testing and the Erichsen method. Corrosion test specimens were tested in a corrosion chamber. An electron microscope was used for more detailed structural analysis. Electron microscope elemental analysis of selected coatings was also included. Based on the information obtained, it proposes a suitable solution in practice, depending on use of the plated component.
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Electrophoresis coating
Holčapek, Jiří ; Kubíček, Jaroslav (referee) ; Žák, Ladislav (advisor)
This bachelor is based on a study of electrophoresis coating and corosion. The first part contains information about corrosion of metal and the importance of protecting metal parts. Then it deals with the technology of electrophoresis coating and technological process of creating electrophoresis coating. Finally, new trends in the field of electrophoresis coating are presented.
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Preparation and characterization of thin barrier layers
Blahová, Lucie ; Mráček, Aleš (referee) ; Buršíková, Vilma (referee) ; Krčma, František (advisor)
Combinations of different acrylic resins and microcrystalline waxes are most often used for the conservation and preservation of metallic archaeological artefacts these days. However, their properties are not sufficient and satisfactory in many ways. Therefore, the aim of this doctoral thesis is to develop a conservation system which will draw on the new knowledge gained in the field of advanced materials and technologies during last years. A conservation coating based on a thin barrier film appears the most promising. The conservation coating must fulfil particularly following rather contradictory requirements: good barrier function against oxygen, humidity and other corrosive agents; transparency because of colour appearance preservation; long term stability and easy removability; possibility to apply to more objects at the same time and reasonable financial requirements of a deposition process. Parylene C polymer was chosen as suitable material for this purpose. It was prepared via modified chemical vapour deposition. Parylene removability was ensured through the soluble interlayer made of Laksil silicone-acrylic lacquer which was applied between the protected metallic object and the parylene thin film. Initially, the deposition process of Laksil/parylene bilayer was optimized, then its physical and chemical characteristics were determined and eventually, they were compared with the conventional conservation coating composed of Paraloid B72 acrylic resin and Revax microcrystalline wax. Regarding to the demands of the conservation coating, we were interested especially in barrier properties, optical properties, surface morphology and removability of Laksil/parylene bilayer. The most useful method for description of coating barrier properties was corrosion testing in which coated metallic samples were exposed to highly corrosive environment of salt spray (made of 50 g•l–1 brine), 100% humidity and temperature of 35 °C (ISO 9227). The Laksil/parylene bilayer showed excellent barrier properties; samples treated this way sustained unchanged in the corrosion chamber for almost three months. The surface roughness measured by profilometry and surface morphology scanned by SEM illustrated the synergy between Laksil and parylene layer which leads to the exceptional barrier and anticorrosion function of bilayer. The Laksil layer is able to flatten out rough surface of a substrate. Furthermore, it can toughen the item surface which is, in case of a number of archaeological findings, created by corrosion product layers with variable mechanical strength. Thereon deposited parylene film becomes smooth and defect free and can act as a good diffusion barrier. The colouristic measurements confirmed that the Laksil/parylene bilayer does not almost change the appearance of protected item, in terms of colour. The caused colour difference (ISO 11664-4) ranged around 1 which value is defined as “perceivable only for experienced observers”. The Laksil/parylene bilayer is removable thanks to the Laksil solubility in xylene. It is necessary to carefully scratch the outer parylene film to enable access of xylene solvent to the lacquer. The successful removal of Laksil/parylene bilayer was first confirmed by the EDX on metallic iron samples. Afterwards, the possibility of bilayer complete removal even from a corroded surface of the original artefact was proved by TGA. Thus the conservation treatment can be considered fully reversible.
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Antikorozní ochrana ocelových konstrukcí
Havránek, Tomáš
The bachelor thesis is focused on description used corrosion systems which we currently use to protection steel structure as well as other products subject to corrosion. About corrosion we talk very often. The corrosion causes big damage to buildings, structures, machinery and other. Understanding the mechanism of corrosion may lead to the development of new and more effective methods of protection. The introduction of this work then speaks about corrosion. The work tries to explain the nature of corrosion. In the middle I describe a technology for the corrosion protection of steel and other materials. Closing part is concentrated on the use of corrosion tests for easy recognition of corrosion mechanisms and factors that cause corrosion and support. The result of these tests can be better estimate of aggression environment against materials and used anticorrosive protection.
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