National Repository of Grey Literature 155 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Effect of aluminum content and precipitation on the corrosion behavior and acoustic emission response of AZ31 and AZ80 magnesium alloys
Veverková, E. ; Knapek, Michal ; Minárik, P.
In this study, we investigated the effect of aluminum content and precipitation on the corrosion behavior of the AZ31 and AZ80 magnesium alloys. The investigated alloys were received in the as-extruded condition in order to retain comparable grain size and texture. First, solid solution treatment was performed on the samples of both alloys. Subsequently, the samples were isothermally aged at 200 degrees C for 20 hours. The scanning electron microscopy was used to study the grain size and microstructure. The corrosion properties of samples were studied by potentiodynamic polarization measurements and the AE signal was concurrently recorded. Solution treated AZ80 and AZ31 samples exhibited similar behavior. The aged AZ80 sample showed lower corrosion rate. Also, a strong breakdown appeared in the later (compared to other samples) stage of the potentiodynamic test. The breakdown was found to be easily recognized by AE parameters.
Oxidation properties of complex concentrated alloys
Veverková, Eliška ; Minárik, Peter (advisor) ; Král, Robert (referee)
The thesis is focused on the oxidation characteristics of two complex con- centrated alloys - FeAlCrMo and FeAlCrV. Potentiodynamic polarisation tests were performed in order to characterize corrosion behavior of the alloys in two different corrosion media (aqueous solution of 3,5% NaCl and 0,5M H2SO4), in addition, high-temperature oxidation resistance was studied. All tests were perfor- med also for stainless steel used as a benchmark. An excellent corrosion resistance of both alloys was discovered, especially in the acidic solution, the studied alloys even surpassed reference stainless steel. On the contrary, poor resistance to high- temperature oxidation was observed. Particularly FeAlCrV exhibited catastrophic properties and resistance of FeAlCrMo is also inferior to stainless steel.
Monitoring of corrosion of refractory lining
Taraba, Vojtěch ; Ptáček, Petr (referee) ; Opravil, Tomáš (advisor)
This bachelor’s thesis is focused on the monitoring of corrosion of refractory lining in the cement rotary kiln, chemical and mineralogical changes of the refractory and their influence on the lining properties. Magnesia-spinel refractories located in the lower transition zone are analyzed by X-ray diffraction, X-ray fluorescence, inductively coupled plasma optical emission spectrometry and scanning electron microscopy.
Effect of humic acid on the corrosion of carbon steel
Horák, Tomáš ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
Bachelor thesis deals with influence of humic acids on corrosion of ČSN 12020 steel. For this purpose, potentiodynamic tests and electrochemical impedance spectroscopy (EIS) in leaches of humic acids, isolated from South Moravian lignite were executed. Results suggest that corrosion is initially promoted by humic acids, but after a longer time (about 98 hours) an inhibitory effect is exerted due to the adsorption of humic acids on the corrosion products. Adsorption efficiency of humic acids on surface of corrosion products was about 30 %. Results also suggest that the presence of humic acids may influence the composition of corrosion products of the steel.
Optical evaluation of corrosion products using colorimetric spectroscopy
Majtás, Dušan ; Fialová, P.
Aim of this work is to test possibility to utilize colorimetric spectroscopy for monitoring the corrosion of lead and tin-lead alloys. And furthermore method suitability for preliminary corrosion evaluation of cultural heritage objects. According to literature colorimetry is used to monitor patinas of bronze objects, thus the method might be also suitable for lead based alloys. Samples used were made from commercially produced lead plate. These were exposed in the climatic chamber to different relative humidity (60, 80, 90 %). After the exposure the corrosion products with different color formed on sample surface. These corrosion products were evaluated by different methods: optical microscopy, colorimetric spectroscopy, and X-ray chemical analysis. Collected colorimetric data display difference between treatments suitable for patina evolution monitoring. The paper presents obtained results and comparison of applied methods.
Corrosion resistance of cast duplex stainless steels
Müller, Peter ; Záděra, Antonín (referee) ; Pernica, Vítězslav (advisor)
The master’s thesis deals with corrosion resistance of cast duplex steels. In the first part the corrosion mechanisms and their individual types are described, the second part characterizes the types of stainless steels in terms of their properties, use, structural components, and their impact on mechanical and corrosion properties of steels. Individual chapter is dedicated to duplex steels. In the experimental part the resistance of 1.4517 steel against pitting corrosion depending on the alloy contents and the PREN value was investigated. Four specimens graded according to PREN were cast. Supplemented with sample stirrer blade which was affected by corrosion during service they were subjected to corrosion test according to ASTM G48-11 standard in 6% FeCl3 solution. Cast specimens were subjected to tensile test and impact test.
Thermal spray by electric arc
Eliáš, Vojtěch ; Sigmund, Marián (referee) ; Kubíček, Jaroslav (advisor)
This thesis deals with the issue of thermal spraying by means of an electric arc. First of all, a theoretical part is processed using a literary study dealing with corrosion and thermal spraying technology. The experimental part contains a description of the technological procedure and evaluation of four thermally sprayed samples. Zinacor 850, consisting of 85% zinc and 15% aluminum, was used as a coating. The evaluation involves measurements of thickness, adhesion and roughness as well as the macro-structural analysis of the coating. Two samples showed unusually low adhesion, and all samples also had a large fluctuation of the measured thicknesses. This was also confirmed by the macro-structural analysis, which showed that the sample with low adhesion also had high porosity. These defects may have multiple causes, but the recommendation for further practice is to reduce the spraying distance from the base material.
Structure and properties of martensitic stainless steels
Rimko, Marcel ; Čamek, Libor (referee) ; Záděra, Antonín (advisor)
The final thesis deals with martensitic stainless steel and their mechanical properties. The theoretical part consists of information about corrosion, chemical composition, heat treatment and mechanical properties of various types of steel. The practical part deals with the influence of the cooling rate during heat treatment and nickel content on the mechanical properties and microstructure of the GX4CrNi13-4 steel.
Manufacture of gastronomic equipment of stainless steel
Macková, Ivana ; Varhaník, Matúš (referee) ; Kalivoda, Milan (advisor)
The bachelor thesis seals with corrosion, stainless steels and surface treatments of steels, which prevent corrosive disruption of the material. Furthermore, the work deals with the design of the production of non-rotating component with a flange made of austenitic stainless steel X5CrNi 18-10. A blank is cut out on sheet shears. A blank is formed into the desire shape on a CYS 320 press by deep drawing technology, and later a flange is cut on LEXN 100 C press. The economic evaluation of production is set at a model situation of 100 000 pcs/year.
Monitoring Of Bridges Corrosion Level
Krejčí, Jakub
Corrosive damage level of bridge constructions becomes high discussed topic with regard to some recent incidents. Current system of inspections is based mostly only on visual inspections in the Czech Republic. Our solution proposes to build-in a humidity sensor inside a bridge structure to detect leaking water and damage level during long period. Text focuses on description of basic principles of humidity measurement and performed experiments with sensors implemented in porous material showing possibility of measurement inside a structure. Finally, a market research of commercially available sensors is documented with narrowing selection suitable for this application.

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