Dissertations / Theses: 'Alkaline corrosion'

1

Been, Jantje. "Titanium corrosion in alkaline hydrogen peroxide environments." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/NQ34511.pdf.

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zhang, peilun. "Zn Corrosion in Alkaline Aqueous Electrolytes: Effect of Electrolyte Composition on Corrosion Rate and Inhibitors to Suppress Corrosion." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1618400150411797.

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Doja, Somi. "Corrosion behaviour of AZ31 magnesium alloy in highly alkaline environments." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61481.

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Magnesium (Mg) and its alloys are known for their high chemical reactivity. This property often poses issues related to undesirable corrosion, or degradation of exposed surfaces. The chemical reactivity of Mg can be also exploited, and as a result Mg alloys often find use as anode materials for fuel cells. However, due to a long term immersion of the anodes in highly alkaline environments, the problem of corrosion remains and needs to be evaluated. Therefore, in this research, the corrosion behavior of a commercially available magnesium alloy AZ31 in 45 wt% potassium hydroxide (KOH), a common electrolyte for alkaline fuel cells, was studied. Immersion tests were performed for a total duration of 20 days to study the growth of corrosion products on the alloy’s surface. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) were carried out to characterize the structure and chemistry of the corrosion products. Also, electrochemical studies were carried out to study the kinetics of corrosion of the AZ31 alloy. Finally, the effect of adding 2 wt% sodium silicate (Na₂SiO₃) to the KOH electrolyte in order to manipulate the corrosion rate was also examined. Tafel analysis confirmed that the corrosion potential of the AZ31 sample immersed in the Na₂SiO₃ + KOH solution reduced by 16% with respect to that of sample immersed in pure KOH. Although the AZ31 alloy contains only a trace amount of nickel, SEM-EDS characterization of the corrosion products revealed that they contained high levels of nickel, with XRD analysis confirming the presence of a nickel hydroxide layer. In the case of the sample immersed in Na₂SiO₃ + KOH electrolyte, an additional layer rich in silicates developed, and likely acted as a barrier for diffusion of ions from surface of the AZ31 sample to the electrolyte. EIS results of modeling the surface corrosion phenomena revealed that a modified Randle’s circuit represented the electrochemical processes occurring on the surface of the alloy. Warburg impedance for the sample immersed in Na₂SiO₃ + KOH was relatively high, suggesting a dissolution of ions from the surface into the highly alkaline KOH electrolyte.
Graduate Studies, College of (Okanagan)
Graduate

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Conrad, Heidi A. Golden Teresa Diane. "Electrochemical deposition of zinc-nickel alloys in alkaline solution for increased corrosion resistance." [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/ark:/67531/metadc12101.

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Zhou, Ting. "Electrodeposition of Molybdenum-Based Coatings from Aqueous Alkaline Solutions for Enhanced Corrosion Resistance." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157641/.

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Zn-Mo coatings are very promising environment friendly anticorrosive coatings as replacement materials for cadmium and chromium (VI) based conversion layers. Electrodeposition has become a favorable technique in fabricating coatings due to its low cost, ease of use, and overall experimental control of coating quality. Very little research so far has been done for the electrodeposition of Zn-Mo coatings under alkaline conditions. In this work, Zn and Zn-Mo coatings were electrochemically deposited on stainless steel from an aqueous alkaline citrate solution. An organic compound, vanillin, was added to the electrolyte as a leveling agent for improving interlayer adherence and corrosion resistance of Zn-Mo coatings. Ni-Mo alloys have been known to possess high tensile strength and excellent corrosion protection of steels, and MoTe2 layers have a potential for the application in anticorrosive coatings due to their hydrophobic properties. In this study, MoTe2-Ni-Mo coatings were deposited on stainless steel using both sputtering and electrodeposition methods. These coatings with high corrosion resistance and other desirable properties are in demand in the oil and gas industry since they can protect and thus extend the lifetime of the underlying materials when exposed to aggressive environments. The Zn-Mo and MoTe2-Ni-Mo coatings were evaluated for chemical composition and corrosion behavior using different types of instrumental and electrochemical techniques. The addition of vanillin to the electrolyte did not change the crystalline structure or composition of the Zn-Mo coating, however, the corrosion resistance of the coating was significantly improved by the leveling effect of vanillin during the electrodeposition. The corrosion resistance of the Ni-Mo coating was also enhanced by applying the hydrophobic MoTe2 monolayer on the top surface.

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Conrad, Heidi A. "Electrochemical Deposition of Zinc-Nickel Alloys in Alkaline Solution for Increased Corrosion Resistance." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12101/.

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The optimal conditions for deposition of zinc-nickel alloys onto stainless steel discs in alkaline solutions have been examined. In the past cadmium has been used because it shows good corrosion protection, but other methods are being examined due to the high toxicity and environmental threats posed by its use. Zinc has been found to provide good corrosion resistance, but the corrosion resistance is greatly increased when alloyed with nickel. The concentration of nickel in the deposit has long been a debated issue, but for basic solutions a nickel concentration of 8-15% appears optimal. However, deposition of zinc-nickel alloys from acidic solutions has average nickel concentrations of 12-15%. Alkaline conditions give a more uniform deposition layer, or better metal distribution, thereby a better corrosion resistance. Although TEA (triethanolamine) is most commonly used to complex the metals in solution, in this work I examined TEA along with other complexing agents. Although alkaline solutions have been examined, most research has been done in pH ≥ 12 solutions. However, there has been some work performed in the pH 9.3-9.5 range. This work examines different ligands in a pH 9.3-9.4 range. Direct potential plating and pulse potential plating methods are examined for optimal platings. The deposits were examined and characterized by XRD.

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Chasse, Kevin Robert. "A study on the mechanism of stress corrosion cracking of duplex stainless steel in hot alkaline-sulfide solution." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/42793.

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Corrosion and stress corrosion cracking of structural components cost an estimated $300 billion annually in the United States alone and are a safety concern for a number of industries using hot alkaline environments. These process environments may contain different amounts of sulfide and chloride; however, the combined role of these ions on the stress corrosion cracking of duplex stainless steels, which are widely used because of their generally reliable performance, had never been studied. This study shows that chlorides in sulfide-containing caustic environments actually have a significant influence on the performance of these alloys. A mechanism for stress corrosion cracking of duplex stainless steels in hot alkaline environments in the presence of sulfide and/or chloride was proposed. Microstructural and environmental aspects were studied using mechanical, electrochemical, and film characterization techniques. The results showed that selective corrosion of the austenite phase depended on percent sulfidity, alkalinity, and chloride content. Chlorides enhanced crack initiation and coalescence along the austenite/ferrite phase boundaries. Unstable passivity of duplex stainless steels in hot alkaline-sulfide environments was due to anion adsorption on the surface leading to defective film formation. Chlorides and sulfide available at the electrolyte/film surface reduced the charge transfer resistance and shifted the response of the films to lower frequencies indicating the films became more defective. The surface films consisted of an outer, discontinuous layer, and an inner, barrier layer. Fe, Mo, and Mn were selectively dissolved in alkaline and alkaline-sulfide environments. The onset of stress corrosion cracking was related to the extent of selective dissolution and was consistent with a film breakdown and repair mechanism similar to slip-step dissolution. Recommendations for reducing the susceptibility of duplex stainless steels to stress corrosion cracking in sulfide-containing caustic environments include reducing the chloride to hydroxide ratio and alloying with less Mo and Mn. The results will impact the petrochemical, pulp and paper, and other process industries as new duplex grades can be developed with optimal compositions and environments can be controlled to extend equipment life.

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Cai, Jiaying, and D. F. Gervasio. "The Nature of Surface Oxides on Corrosion-Resistant Nickel Alloy Covered by Alkaline Water." SpringerOpen, 2010. http://hdl.handle.net/10150/610223.

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A nickel alloy with high chrome and molybdenum content was found to form a highly resistive and passive oxide layer. The donor density and mobility of ions in the oxide layer has been determined as a function of the electrical potential when alkaline water layers are on the alloy surface in order to account for the relative inertness of the nickel alloy in corrosive environments.

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Abosrra, L. R. "Corrosion of steel reinforcement in concrete : corrosion of mild steel bars in concrete and its effect on steel-concrete bond strength." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/5417.

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This thesis reports on the research outcome of corrosion mechanism and corrosion rate of mild steel in different environments (saline, alkaline solutions and concrete media) using potentiodynamic polarization technique. The study also included the effect of corrosion on bond strength between reinforcing steel and concrete using pull-out test. Corrosion of mild steel and 316L stainless steel with different surface conditions in 1, 3 and 5% saline (NaCl + Distilled water) was investigated. Specimens ground with 200 and 600 grit silicon carbide grinding paper as well as 1μm surface finish (polished with 1μm diamond paste) were tested. In case of mild steel specimens, reduction in surface roughness caused increase in corrosion rate, while in 316L stainless steel corrosion rate decreased as the surface roughness improved. Metallographic examination of corroded specimens confirmed breakdown of passive region due to pitting corrosion. Corrosion of mild steel was also investigated in alkaline solution (saturated calcium hydroxide, pH =12.5) contaminated with 1, 3 and 5% saline. A series of corrosion experiments were also conducted to examine the efficiency of various concentrations of calcium nitrite (CN) on corrosion behaviour of both as-received and polished mild steel in alkaline solution containing 3% saline after 1 hour and 28 days of exposure. Corrosion rate was higher for the as-received than polished mild steel surface under the same testing conditions in NaCl alkaline solution with and without nitrites due to the effect of surface roughness. Morphology investigation of mild steel specimens in alkaline solution ii containing chlorides and nitrites showed localized pits even at nitrite concentration equal to chloride concentration. Corrosion of steel bars embedded in concrete having compressive strengths of 20, 30 and 46MPa was also investigated. The effect of 2 and 4% CN by weight of cement on corrosion behaviour of steel bar in low and high concrete strengths specimens were also studied. All reinforced concrete specimens were immersed in 3% saline solution for three different periods of 1, 7 and 15 days. In order to accelerate the chemical reactions, an external current of 0.4A was applied. Corrosion rate was measured by retrieving electrochemical information from polarization tests. Pull-out tests of reinforced concrete specimens were then conducted to assess the corroded steel/concrete bond characteristics. Experimental results showed that corrosion rate of steel bars and bond strength were dependent on concrete strength, amount of CN and acceleration corrosion period. As concrete strength increased from 20 to 46MPa, corrosion rate of embedded steel decreased. First day of corrosion acceleration showed a slight increase in steel/concrete bond strength, whereas severe corrosion due to 7 and 15 days corrosion acceleration significantly reduced steel/concrete bond strength. Addition of only 2% CN did not give corrosion protection for steel reinforcement in concrete with 20MPa strength at long time of exposure. However, the combination of good quality concrete and addition of CN appear to be a desirable approach to reduce the effect of chloride induced corrosion of steel reinforcement. At less time of exposure, specimens without CN showed higher bond strength in both concrete mixes than those with CN. After 7 days of corrosion acceleration, the higher concentration of CN gave higher bond strength in both concrete mixes. The same trend was observed at 15 days of corrosion acceleration except for the specimen with 20MPa compressive strength and 2% CN which recorded the highest deterioration in bond strength.

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Pismenny, Arthur. "Stray current corrosion of carbon steel, electroplated nickel, and electroless nickel in an alkaline environment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ63142.pdf.

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Silva, Oriana Susete Martins da. "Otimização do rendimento de uma linha de tratamentos eletrolíticos." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/16912.

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Mestrado em Engenharia Química
A corrosão é um problema frequente nos materiais. De modo a evitá-la um dos principais métodos é a aplicação de revestimentos protetores no qual ocorre a eletrodeposi-ção de um metal sobre o metal a proteger, destinando-se a conferir propriedades como durabilidade, resistência, pro-teção e aspeto. Este trabalho teve como objetivo otimizar o rendimento de uma linha de tratamentos eletrolíticos, para revestimentos em zinco alcalino ou zinco-níquel. Para tal foram planeados vários conjuntos de experiências, nos quais os valores dos fatores supostos serem os mais significativos para o resultado final foram escolhidos obe-decendo a um planeamento fatorial, tendo os resultados sido obtidos numa célula de Hull. Realizaram-se quatro fases de ensaios acerca do banho de zinco-níquel e duas sobre o banho de zinco alcalino. Atra-vés das respostas obtidas após a eletrodeposição na célula de Hull, foi possível avaliar a importância de fatores como a temperatura do banho, o tempo de eletrodeposição, a in-tensidade da corrente e as concentrações dos principais reagentes em causa. A principal conclusão é referente ao tempo de eletrodepo-sição, pois este é o fator com um maior impacto perante o processo em estudo. O aumento do tempo de eletrodepo-sição origina um aumento nas espessuras das camadas depositadas de zinco-níquel e de zinco alcalino. Os resultados obtidos permitiram ainda concluir que a di-minuição da concentração de zinco, proporciona um au-mento na percentagem em peso de níquel na liga de Zn-Ni depositada.
Corrosion is a common problem that affects most metallic materials. In order to avoid it one of the main methods is the application of protective coatings which can be the electrodeposition of a metal or alloy into the metallic sur-face to be protected. These coatings are designed to im-prove the protection, strength, durability and appearance of the protected item. The propose of this thesis is to optimize the yield of an electrolytic line for alkaline zinc and zinc-nickel coatings. To achieve this goal, several sets of experiences were planned, in which the values of factors that supposed to influence the outcome were chosen according to an ex-perimental design scheme (full factorial), and conducted in a Hull cell. There were two sets for the alkaline zinc bath and four sets for the zinc-nickel bath, and from the results of the Hull cell, it was possible to access the significance of the factors temperature of the bath, time of electrodeposition, intensity of current and concentrations of the main rea-gents used, in the thickness of the zinc-nickel and alkaline zinc layers, and percent weight of nickel in the same layer. The main conclusion is that the deposition time is the most significant factor and when it increases the thickness of the layers deposited increases as expected. It should also be noted that when the zinc concentration decreases the weight percentage of nickel in the depos-ited zinc-nickel alloy increases.

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Scheffler, Christina. "Zur Beurteilung von AR-Glasfasern in alkalischer Umgebung: Evaluation of AR-glas fibres in alkaline environment." Doctoral thesis, Leibniz-Institut für Polymerforschung Dresden e.V, 2009. https://tud.qucosa.de/id/qucosa%3A25230.

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AR-Glas wird in Form von Multifilamentgarn zur Verstärkung in textilbewehrtem Beton eingesetzt. Während des Herstellungsprozesses wird auf die AR-Glasfilamente die Schlichte aufgebracht, deren chemische Zusammensetzung maßgeblich die Qualität der Filament-Matrix-Grenzschicht bestimmt, sowie die chemische Beständigkeit im alkalischen Milieu gewährleistet. Zur Beurteilung der chemischen Beständigkeit in alkalischer Umgebung werden beschleunigte Alterungsversuche in wässrigen, alkalischen Lösungen durchgeführt. Die Reaktion von Hydroxid-Ionen mit dem Si-O-Si-Gruppen des Glasnetzwerkes führt zur Ausbildung hydratisierter Oberflächen und gelösten Silikaten. Das Ausmaß der Glaskorrosion ist von der chemischen Zusammensetzung der Glasfaser, der Schlichte bzw. Beschichtung und der alkalischen Lösung sowie von Zeit und Temperatur abhängig. Die beschleunigte Alterung von verschiedenen AR-Glasfasern in NaOH-Lösung sowie Zementlösung zeigt, dass sich der Korrosionsmechanismus aufgrund der vorhandenen Calcium-Ionen unterscheidet. Die Filamentbruchspannung wird anhand der Weibull-Verteilungsfunktion analysiert. Das mechanische Verhalten hängt deutlich von der chemischen Zusammensetzung der Alterungslösung ab, was zu unterschiedlichen Parametern der Weibull-Verteilungsfunktion sowie vermengten Verteilungen führen kann. Die Alterung in NaOH-Lösung führt zur Ausbildung einer korrodierten Schicht an der Filamentoberfläche. In Ca-haltigen Zementlösungen kommt es dagegen zu einer lokal begrenzten Korrosion. Für die Beurteilung verschiedener Polymerbeschichtungen werden Betonverbunde bei unterschiedlichen Temperaturen und Umgebungsfeuchten gelagert, wodurch geeignete Alterungsbedingungen evaluiert werden und den Vergleich der chemischen Beständigkeit unterschiedlicher Beschichtungen ermöglichen.
Rovings made of AR-glass are used in textile reinforced concrete. During the manufacturing process the sizing is applied on the AR-glass filaments. The chemical constitution of the sizing determines the quality of the filament-matrix-interface but also the chemical durability of the glass filaments in alkaline environment. The durability is evaluated by accelerated ageing tests in aqueous, alkaline solutions. In alkaline solutions, the reaction of hydroxyl ions with Si-O-Si-groups of the glass network leads to the formation of hydrated surfaces and dissolved silicate. The rate of this corrosion depends on the chemical constitution of the fibre and the alkaline solution as well as on time and temperature. The investigation of the ageing of glass fibres with different chemical constitutions in NaOH and cement solutions shows that the corrosion mechanism changes due to the inhibiting effect of calcium ions. The strength distributions have been evaluated using a Weibull distribution function. The mechanical behaviour strongly depends on the chemistry of the solution and determines the parameters of the Weibull distribution function in terms of either single or mixed distributions. The corrosion in NaOH solution leads to a strong dissolution of the outer layer of the glass fibres, whereas during aging in cement solution at the same pH-value a limited, local attack was revealed. The evaluation of polymer coatings is realised by the ageing of concrete composites at different temperatures and humidities to deduce adequate ageing conditions for the comparison of different coatings.

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Doche, Marie-Laure. "Étude d'anodes pour générateur aluminium-air à électrolyte alcalin." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0024.

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Au cours des dernieres annees, le generateur aluminium - air a ete etudie, particulierement pour son application a la propulsion de vehicules electriques. L'aluminium presente en effet une energie theorique importante (8 kw. H/kg) et son utilisation en pile pourrait permettre d'augmenter l'autonomie d'un vehicule. La premiere partie du travail concerne l'etude technologique de ces generateurs utilisant l'electrolyte naoh. Elle a ete realisee sur une cellule aluminium - air pilote (1 v / 70 a), et a permis de degager les parametres essentiels (concentration en soude, temperature, concentration en inhibiteurs de corrosion. . . ) du fonctionnement de l'anode. Le rapport cout de l'alliage/performances en decharge a ete optimise en utilisant la methodologie experimentale des plans d'experiences. Il s'avere que le materiau d'anode habituellement utilise (aluminium 5n) peut etre avantageusement remplace par une nuance 3n5 moins chere, tout en garantissant des caracteristiques en puissance sensiblement equivalentes. Le maintien des performances, en cours de decharge prolongee, exige toutefois d'associer un volume important d'electrolyte au module electrochimique. La masse du systeme parait alors exclure une integration sur vehicule electrique ; le generateur reste adapte a une utilisation sur site fixe. La seconde partie du travail presente une analyse a caractere plus fondamental des mecanismes de dissolution - corrosion de l'aluminium en milieu concentre en soude. Un montage experimental original a permis de determiner, par mesure en continu du degagement d'hydrogene, la contribution du courant de corrosion au courant total de dissolution de l'anode. L'obtention de courbes de polarisation decorrelees permet d'analyser separement les cinetiques des deux reactions partielles qui ont lieu a la surface de l'aluminium. Le caractere passif de l'aluminium en milieu sodique tres concentre est mis en evidence. Les resultats obtenus dans des conditions experimentales, mettant en jeu les differents parametres de fonctionnement de la pile, permettent de rendre compte de l'effet de la temperature, des conditions hydrodynamiques, des impuretes et de la presence d'ions aluminate et stannate en solution, sur les cinetiques des deux reactions d'oxydation de l'aluminium et de degagement d'hydrogene.

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FONTES, ERIC H. "Oxidação eletroquímica do etanol utilizando eletrocatalisadores PtRh/C em meio alcalino e sintetizados via borohidreto de sódio e redução por álcool." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28013.

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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-16T17:36:39Z No. of bitstreams: 0
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Os eletrocatalisadores PtRh/C foram preparados nas seguintes proporções atômicas: (100,0), (0,100), (90,10), (70,30) e (50,50). Os métodos empregados nas sínteses foram redução via borohidreto de sódio e redução por álcool. Os sais metálicos empregados foram H2PtCl6.6H2O e (RhNO3)3 e o suporte de carbono utilizado foi carbon Vulcan XC72, a composição metálica em massa foi de 20%; e o suporte, 80%. Os eletrocatalisadores foram caracterizados por técnicas físico-químicas, espectroeletroquímica e por experimento em célula a combustível, cujo emprego se deu por uma célula unitária direta a álcool com membrana alcalina. Os eletrodos de trabalho foram preparados pela técnica de camada fina porosa. A técnica de difração de raios X permitiu verificar ligas metálicas, fases segregadas e calcular a porcentagem de ligas metálicas, bem como constatar os tipos de fases cristalinas. A técnica de espectroscopia no infravermelho permitiu verificar que a oxidação eletroquímica do etanol se dá pelo mecanismo indireto de oxidação, ou seja, para todos materiais estudados houve a produção de espécies intermediárias, em que PtRh(70:30)/C sintetizado pelo médodo de redução via borohidreto de sódio produziu grandes quantidades de CO2 e C2H4O. Rh/C mostrou-se ativo eletroquimicamente para ambos os métodos de síntese empregados. A técnica de microscopia eletrônica de transmissão permitiu calcular o tamanho médio e a área superficial média dos eletrocatalisadores. As técnicas eletroquímicas permitiram verificar a estabilidade, potencial onset e pares redox dos sistemas considerados.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

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Pickrell, Gary Robert. "High temperature alkali corrosion kinetics of low expansion ceramics /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-163208/.

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Pickrell, Gary R. "High temperature alkali corrosion kinetics of low expansion ceramics." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/38220.

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Holloway, Mark. "Corrosion of steel reinforcement in slag-based concrete." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365811.

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Viklund, Peter. "High temperature corrosion during waste incineration : characterisation, causes and prevention of chlorine-induced corrosion." Licentiate thesis, Swerea KIMAB AB, Stockholm, Sweden, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32412.

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Waste-fired boilers suffer severely from corrosion of critical components such as superheater tubes. In this work the high temperature corrosion of candidate superheater alloys have been investigated by detailed laboratory studies and controlled field exposures in full-scale boilers. In a laboratory study the detrimental effect of gaseous hydrochloric acid (HCl) on three different ground surface and preoxidised austenitic stainless steels was investigated. Exposures were conducted in an environment comprising N2-10O2-5H2O-0.05HCl at both 400 °C and 700 °C. A positive effect of preoxidation is evident when the alloys are exposed at 400 °C. Oxide layers formed during preoxidation effectively suppress chlorine ingress and lower the corrosion rate for all three materials while accelerated corrosion and chlorine accumulation at the metal/oxide interface is detected for ground surface specimens. The positive effect of preoxidation is lost at 700 °C and corrosion resistance is dependent on alloying level. At 700 °C metal chloride evaporation contributes significantly to the material degradation. Based on the results, high temperature corrosion in the presence of gaseous HCl is discussed in general terms. In two different waste-fired boilers measures for counteracting superheater corrosion were investigated. In a grate-boiler the deposit formation and high temperature corrosion of some candidate superheater materials were studied. Metal loss measurements showed unacceptably high corrosion rates for the lower alloyed ferritic steels 13CrMo44 (Fe-1Cr-0.5Mo) and HCM12A (Fe-11Cr-2W), as well as for the austenitic Super 304 (Fe-18Cr-9Ni-3Cu). The corrosion attack for these alloys was manifested by the formation of mixed metal chloride/metal oxide scales. A different type of behaviour was seen for the higher alloyed austenitic steels and nickel-base alloys, which were able to form a chromium-enriched oxide next to the metal. However, the alloys suffered from localised pitting attack. Since analyses of the deposit revealed appreciable amounts of low melting salt mixtures such as ZnCl2-KCl, PbCl2-KCl, FeCl2-KCl and NaCl-NiCl2, oxide dissolution in these molten salts is the probable reason for pitting attack. In a waste-fired boiler ammonium sulphate solution was added to the flue gas and the effect on flue gas and deposit composition was evaluated. It was evident that the sulphur-rich additive reduced the amount of alkali chlorides in both the flue gas and the deposit. Results also indicated that the initial corrosion rates were lowered with the use of ammonium sulphate. It was concluded that using the additive could be a possible strategy for changing the flue gas chemistry so that superheater corrosion is mitigated.

QC 20110414

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Nguyen, Thierry Huu Chi. "CMZP and Mg-doped Al2TiO5 Thin film Coatings for High Temperature Corrosion Protection of Si3N4 Heat Exchangers." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36628.

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Silicon nitride (Si3N4) is a potentially good ceramic material for industrial heat exchangers. However, at elevated temperatures and in coal combustion atmospheres its lifetime is severely reduced by oxidation. To increase its corrosion resistance, the formation of a protective oxidation barrier layer was promoted by the deposition of oxide thin films. Homogeneous and crack-free oxide coatings of calcium magnesium zirconium phosphate (CMZP) and magnesium doped aluminum titanate (Mg-doped Al2TiO5) were successfully deposited on Si3N4 using the sol-gel and dip-coating technique. Coated and uncoated samples were then exposed to a sodium containing atmosphere at 1000*C for 360 hours to simulate typical industrial environment conditions. Structural post-exposure analyses based on weight loss measurements and mechanical tests indicated better corrosion resistance and strength retention for CMZP coated Si3N4 compared to as received and Mg-doped Al2TiO5 coated Si3N4. This difference was attributed to the protective nature of the corrosion layer, which in the case of CMZP, significantly impeded the inward diffusion of oxygen to the Si3N4 surface.
Master of Science

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Persson, Kajsa. "High temperature corrosion on heat exchanger material exposed to alkali salt deposits." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-104121.

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Power generation through decentralized small scale CHP would facilitate the use of biomass as an energy source, with the externally fired gas turbine (EFGT) being a promising technology due to its high electrical efficiency. In an EFGT hot flue gases are heat-exchanged with an air cycle, driving the turbine. The operation requires higher flue gas temperatures than other technologies, for example steam turbines, to achieve optimal performance. The operating conditions subjects the high temperature heat exchanger (HT-HE) to both physical and chemical stress, with the corrosion related issues yet to be solved. Problems concerning deposit formation and corrosion, on for example super heaters and heat exchangers, when firing biomass are important issues even in commercially available technologies, where the choice of fuel and fuel additives together with component design and choice of material plays important roles in order to minimize the problems. The significantly higher temperatures of the heat transferring surfaces for an EFGT entails combustion deposit related problems less studied. The evaluation of turbine control, deposit formation and corrosion as well as design of the HT-HE and system integration will enable the development of the EFGT technology for applications with small- and medium-size biomass combustion. In this work four potential HT-HE alloys of various grades have been evaluated with respect to corrosion resistance, when exposed to alkali salts and salt mixtures in the KCl-K2CO3-K2SO4 system. The exposures were done in a tube furnace during 24 h for each experiment at four temperature levels between 700–1000oC. Morphological and elemental analysis of the alloy surface and corrosion layers was performed with SEM-EDS. The presence of KCl in the salt caused the most severe corrosion attacks while the corrosion attacks of the pure sulfate and carbonate were more modest. Significant differences between the four materials were observed. X20 experienced severe corrosion, with corrosion scale formation in most cases. The KCl-containing salts caused 253MA to form corrosion scales at all temperatures, while the corrosion resistance to other salts was fairly good. Inconel 600 had the second best overall corrosion resistance. However, it should be pointed out that in some cases the alloy was surpassed by 253MA. Kanthal showed the best overall performance, with limited corrosion scale formation and surprisingly high corrosion resistance to the KCl-containing ternary salt mixture at 900°C and 1000°C.

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Погребова, Інна Сергіївна. "Наукові основи створення синергетичних адсорбційних інгібіторів корозії поліфункціонального призначення." Doctoral thesis, Київ, 2021. https://ela.kpi.ua/handle/123456789/45499.

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Дисертація присвячена вирішенню важливої науково-технічної проблеми: підвищенню корозійної стійкості та експлуатаційно-технічних властивостей металевих виробів, устаткування та пристроїв шляхом використання синергетичних адсорбційних інгібіторів корозії широкого спектру захисної дії. Розроблено науково-обґрунтований підхід до створення ефективних інгібіторів корозії на основі поліфункціональних органічних сполук та комбінацій органічних сполук і солей металів. Підхід базується на комплексному дослідженні процесів адсорбції, встановленні взаємозв’язку між будовою органічних сполук, їх адсорбційними захисними властивостями, визначенні особливостей кінетики парціальних реакцій конкретних видів корозії і шляхів впливу на них інгібіторів, врахуванні ефектів внутрішньомолекулярного і міжмолекулярного синергізму, які виникають при інгібуванні корозії. Досліджено закономірності адсорбції та захисної дії при кислотній корозії заліза та вуглецевих сталей різних за хімічним складом монофункціональних і поліфункціональних органічних сполук. Виявлена роль амінних, піридинієвих, карбонільних, тіокарбонільних, карбоксильних груп в захисній дії цих інгібіторів. Розвинені сучасні наукові положення щодо механізму захисної дії органічних інгібіторів корозії та ролі різних частинних ефектів її інгібування. Запропоновано і експериментально обґрунтовано рівняння, яке встановлює взаємозв’язок між кінетичними параметрами корозійних процесів, захисною дією інгібіторів та їх адсорбційними властивостями з урахуванням механізму анодного розчинення заліза. Досліджено і науково обґрунтовано ефекти внутрішньомолекулярного і міжмолекулярного синергізму, які виникають при інгібуванні корозії металів поліфункціональними органічними сполуками з атомами Нітрогену, Оксигену, Сульфуру та сумішами органічних і неорганічних сполук різного механізму захисної дії. Встановлено, що амінні та піридинові фрагменти поліфункціональних органічних сполук забезпечують їх захисну дію за енергетичним механізмом при невисоких температурах, а тіокарбонільних та карбоксильних – при підвищених. Висвітлено взаємозв’язок між характером сил взаємодії між адсорбованими частинками та їх захисною дією при кислотній корозії заліза. Запропоновано новий тип синергетичних інгібіторів кислотної, сольової та лужної корозії цинку на основі сумішей органічних сполук і катіонів металів. Встановлено роль модифікації поверхневих властивостей цинку, що відбувається внаслідок протікання різних електрохімічних процесів в захисній дії цього типу інгібіторів корозії. Розроблена модель адсорбції органічних сполук на металах, заснована на уявленнях про утворення комплексів з частинним переносом заряду та прогнозуванні її протікання з використанням принципу ЖМКО Пірсона. На підставі застосування запропонованої моделі адсорбції розроблено напрямки створення нових ефективних інгібіторів корозії, засновані на врахуванні адсорбційних властивостей металів, специфіки механізмів корозії, ефектів синергізму їх захисної дії. Розроблено нову серію органічних інгібіторів корозії на основі четвертинних піридинієвих солей з карбонільними групами широкого спектру дії і поліфункціонального призначення (кислотна корозія, мікробна корозія металів в умовах бактеріальної сульфатредукції, кислотне корозійно-механічне руйнування сталей). Досліджено взаємозв’язок між захисною дією органічних сполук, електронними та стеричними властивостями їх замісників та природою додаткових функціональних угрупувань, схильних до безпосередньої адсорбції на сталі. Виявлено роль біологічного та електрохімічного факторів при інгібуванні корозії металів в умовах бактеріальної сульфатредукції. Науково обґрунтовано ефект синергізму захисної дії органічних сполук під впливом продуктів метаболізму бактерій (HS - , H S). Досліджено вплив інгібіторів на саморозряд, електричні та розрядні 2 характеристики цинкових та кадмієвих анодів хімічних джерел струму. На підставі використання розроблених інгібіторів корозії запропоновано удосконалені свинцево-цинкові та свинцево-кадмієві елементи з кислотними електролітами, марганцево-цинкові елементи водно-сольової та водно-лужної системи. Встановлена перспективність застосування комбінованого протикорозійного захисту вуглецевих сталей в водних агресивних середовищах на основі сумісного використання дифузійних покриттів та інгібіторів корозії.

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22

Wen, Hong Xing. "Prediction of structural effects in concrete affected by alkali-aggregate reaction." Thesis, University of Plymouth, 1993. http://hdl.handle.net/10026.1/2020.

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Alkali-aggregate reaction (AAR) is a chemical reaction between alkalis in concrete and certain alkali-reactive substances which are occasionally present in the aggregate. AAR produces a gel, which absorbs water, swells, inserts local stresses, and causes internal and external cracking in the concrete. Research on the reaction has been extensive. However, little research into the structural effects of AAR has been carried out and the effects are not yet adequately understood. The present research is to investigate the structural effects of AAR and to develop a numerical method for the analysis of the affected members. AAR affects the structural performance of reinforced concrete members in the following ways. • The expansion of AAR induces stresses in concrete and reinforcement and alters the bond stresses between the reinforcement and concrete. • AAR changes the material properties of the concrete. • AAR changes the bond properties between reinforcement and the concrete. To analyse an AAR affected member, the expansions within the member due to AAR have to be known. The main feature of AAR expansion is its stress dependency. This necessitates an expansion analysis to take into account the expansion and stress history of the concrete. A model for AAR expansion analysis is proposed, in which the basic variable is the free expansion and the restrained expansion of a concrete is governed by an instantaneous stress-expansion relationship. This model has been proved to yield good results. Experimental work to verify the assumptions made in the expansion model and also provide information on the deterioration of material properties of the affected concrete is described Material models are proposed based on the test results. The expansion model and the material models have been incorporated into a non-linear finite element computer program. Analytical results show good agreement with test data. The results of numerical studies carried out on singly reinforced beams conditioned with and without loading are given. The characteristics of structural performance of the beams found in the numerical studies are in general agreement with those found in laboratory and field testing. The numerical studies have helped to improve understanding of the effects of AAR on structural members. The method developed could be used to assist the future research and the appraisal of in-situ affected structures.

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Ahmed, Tariq Mohamed Ali. "The behaviour of alkali-silica reactive concrete under high point load and under cyclic loading." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338999.

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24

Kang, Min. "Alkali/steam corrosion resistance of commercial SiC products coated with sol-gel deposited Mg-doped Al₂TiO₅ and CMZP." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/42006.

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The corrosion resistance of two commercially available SiC filter materials coated with Mg-doped Al₂ Ti0₅ and (Ca _0.6.6' Mg_0.52) Zr₄P₆0₂₄ (CMZP) was investigated in high-temperature high pressure (HTHP) alkali-steam environments. Coated specimen properties, including cold and hot compressive strengths, bulk density, apparent porosity, permeability, and weight change, dete~ed after exposure to 92% air-S% steam 10 ppm Na at 8OOÂ°C and 1.8 MPs for 500 h were compared with those of uncoated specimens. Procedures for applying homogeneous coatings of Mg-doped Al₂ Ti0₅ and CMZP to porous SiC filters were established and coating of the materials was successfully accomplished. Efforts to stabilize the Al₂ Ti0₅ coating composition at elevated temperature were successful. Coatings show promise for providing improved corrosion resistance of the materials in pressurized fluidized bed combustion (PFBC) environments as evidenced by higher compressive strengths exhibited by coated SiC specimens than by uncoated SiC specimens following HTHP alkali-steam exposure.
Master of Science

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25

Broström, Markus. "Aspects of alkali chloride chemistry on deposit formation and high temperature corrosion in biomass and waste fired boilers." Doctoral thesis, Umeå universitet, Energiteknik och termisk processkemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-33667.

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Combustion of biomass and waste has several environmental, economical and political advantages over the use of fossil fuels for the generation of heat and electricity. However, these fuels often have a significantly different composition and the combustion is therefore associated with additional operational problems. A high content of chlorine and alkali metals (potassium and sodium) often causes problems with deposit formation and high temperature corrosion. Some different aspects of these issues are addressed in this thesis. The overall objective of this thesis was to study and highlight different means by which operational problems related to alkali chlorides can be overcome, reduced or prevented. The most important results of this thesis are: (1) A full description of the in-situ alkali chloride monitor, its operational principles, the calibration procedure, and an example of a full-scale application was made public in a scientific publication. (2) Efficient sulfation of gaseous alkali chlorides in a full-scale boiler was achieved by injecting ammonium sulfate in a water solution into the hot flue gas. (3) Reduced deposit growth and corrosion rates were achieved by lowering the alkali chloride concentration in the flue gas by sulfation. (4) Evidence of decreased deposit growth and chlorine content in deposits during peat co-combustion. (5) Results are presented from high temperature corrosion tests with different superheater steels in two different combustion environments. (6) Controlled KCl and NaCl condensation under simulated combustion conditions resulted in deposits which consisted of mostly pure phases, in contrast to the solid solution that would be expected under the prevailing conditions at chemical equilibrium.

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Majlesi, Yasin. "A laboratory investigation into the structural performance and mechanical properties of plain and reinforced concrete elements affected by alkali silica reaction." Thesis, Queen Mary, University of London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313114.

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The object of this study was to help clarify some of the fundamental problems occurring in plain and reinforced concrete structural elements suffering from the degradation phenomenon of alkali silica reaction. A laboratory based testing programme was used, so that extreme conditions for generating alkali silica reaction could be used which are not readily achieved in actual structures. Special concrete mixes were also used in which the alkali silica reaction occurs within a period of months rather than years so that observation of the properties of the reacted concrete could be taken throughout the reacti ve process. The laboratory tests undertaken are as follows: fresh and hardened behaviour of alkali silica reactive (ASR) model mixes; mechanical properties and expansion behaviour of ASR concrete; structural behaviour of reinforced ASR concrete beams and columns; bond between reinforcement and ASR concrete in prisms and beams; restraint effect of ASR upon plain and reinforced concrete structural elements. This work shows that, ASR causes an unacceptable level of progressive damage to plain and reinforced concrete. The degradation and expansion in plain ASR concrete is higher than that in reinforced concrete. ASR in concrete reduces the strength and elastic modulus; the stiffness of reinforced beams; the axial load and ultimate bending moment capacity of columns; the ultimate bond between concrete and reinforcement. As a result of expansion in non-symmetrically reinforced structural elements, ASR causes either sagging or hogging displacement. The restraint imposed by reinforcement in ASR concrete elements is however beneficial in terms of inhibiting expansion and crack development, and exerting a small degree of post tensioning which generally improves the strength of members. Preloading of ASR concrete also results in an improvement in the mechanical properties. PhD

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Rifai, Farah. "Immobilisation de déchets magnésiens dans un matériau alcali-activé : étude expérimentale et numérique." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN043/document.

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Le travail décrit dans ce manuscrit s’inscrit dans le cadre de la gestion de déchets nucléaires, de faible activité à vie longue (FA-VL), composés d’alliage de magnésium et de graphite, produits pendant l’exploitation de la première génération de réacteurs nucléaires en France. Il s’agit d’étudier la possibilité de leur immobilisation par cimentation et de comprendre le comportement des colis ainsi fabriqués tout au long de leur vie. Plusieurs mécanismes couplés sont à considérer : l’alliage de magnésium peut se corroder au sein de la matrice d’enrobage, en particulier lors du couplage galvanique avec le graphite. La croissance de produits de corrosion autour du métal et la restriction des déformations propres de la matrice cimentaire engendrent des contraintes à l’intérieur du matériau. La vérification de certaines exigences de sureté (stabilité dimensionnelle du colis et faible production d’hydrogène) nécessite donc le développement d’un outil numérique pouvant prédire le comportement mécanique des colis. En particulier, un mortier de laitier activé à la soude, qui présente un intérêt particulier, est examiné. Ce liant appartient à la famille des matériaux alcali-activés dont la modélisation numérique du comportement est peu abordée dans la littérature. La construction du modèle numérique passe ainsi par une large campagne expérimentale (caractérisation du comportement thermo-chemo-mécanique du mortier de laitier alcali-activé et de la corrosion du magnésium dans les matrices cimentaires) puis par un travail d’homogénéisation par éléments finis pour pouvoir déterminer les propriétés de l’ensemble (mortier + déchets) et mener des simulations à l’échelle du colis. Concernant le premier axe d’étude expérimentale, un faible échauffement accompagne l’avancement des réactions d’hydratation, ce qui est bénéfique vis-à-vis des contraintes internes résultantes de l’auto-restriction des déformations thermiques au sein des structures massives. Néanmoins, les déformations de retrait endogène montrent un développement important à long terme. Ceci peut générer des contraintes internes dans le colis (en présence de restrictions), mais la grande capacité de fluage du matériau empêche la fissuration. Concernant le deuxième axe d’étude expérimentale, le mortier de laitier activé est comparé avec deux autres mortiers à base de CEM I, pour évaluer le comportement à la corrosion de l’alliage de magnésium. Les observations microscopiques montrent que la corrosion galvanique de l’alliage est particulièrement agressive dans les mortiers à base de CEM I (corrosion localisée se manifestant par des creusements et des microstructures en feuillets) contre une corrosion uniforme, mais faible dans le mortier de laitier alcali-activé. La cinétique de corrosion est déterminée en utilisant des techniques gravimétriques et électrochimiques. Les résultats de ces deux types de mesure sont complémentaires et témoignent également d’une faible corrosion dans le mortier de laitier activé. De plus, ils montrent une certaine passivation du métal au-delà de 6 mois d’enrobage. Cette propriété spécifique du mortier de laitier activé peut être expliquée par une grande résistivité électrique par rapport aux mortiers de CEM I déterminée en analysant les données de spectroscopie d’impédence électrochimiques. Ensuite, des premières simulations simplifiées par éléments finis à l’échelle mésoscopique sont effectuées sur Cast3m, pour modéliser l’effet mécanique du développement de la corrosion sur le mortier d’enrobage. Plusieurs paramètres sont intégrés comme la cinétique de corrosion de l’alliage ainsi que la nature des produits formés et leurs propriétés mécaniques, identifiées par des observations MEB/EDS et nano-indentation. Les résultats indiquent que les contraintes générées dans la matrice d’enrobage n’entrainent pas d’endommagement
The operation phase of the first generation of nuclear reactors in France has generated magnesium and graphite long lived low-level wastes (LLW-LL). Their conditioning in a hydraulic binder matrix is being addressed. In order to study the behavior of these packages, several coupled mechanisms have to be considered: the magnesium alloy can corrode within the encapsulating matrix, especially when galvanic coupling with the graphite occurs. The corrosion of the metal results in the development of corrosion products. The growth of corrosion products around the metal and the restriction of the hydraulic binder’s delayed strains may lead to the generation of internal stresses. The verification of certain safety requirements (dimensional stability of the package and low hydrogen production) is therefore essential. It requires the development of a numerical model able to predict the behavior of these packages.In particular, a sodium hydroxide activated blast furnace slag mortar is being addressed. It belongs to the family of alkali-activated materials for which the modelling of ageing behavior is rarely approached. Hence, the construction of the numerical model involves a large experimental campaign covering the thermo-chemo-mechanical behavior of the alkali-activated mortar and the corrosion of magnesium in hydraulic binders. Meso-scale homogenization calculations are undertaken in order to determine upscaled properties of the mix (matrix + wastes) and carry out simulations on the scale of the packages.Regarding the first experimental study axis, a relatively low hydration heat is measured. This is beneficial with respect to the internal stress generated from the self-restriction of the thermal strains within massive structures.Nevertheless, the materials undergoes a particular autogenous shrinkage strains showing an increase even at long term. However, its basic creep strains are shown to be important which could result in stress relaxation and avoids damage related to shrinkage restriction.Regarding the metal’s corrosion behavior in the alkali-activated mortar, it is compared to the one in two different ordinary Portland cement (OPC) based mortars. Microscopic observations are conducted on samples especially designed to monitor the galvanic corrosion of the alloy. They show the aggressiveness in OPC mortars (localized corrosion manifested by holes and layered microstructure) against limited homogeneous corrosion in alkali-activated mortar. Additionnaly, corrosion kinetics are determined using different experimental methods: mass loss and electrochemical measurements. The complementary results of these two types of measurements also show a low corrosion in the alkali-activated slag mortar with a passive state of the metal achived at 6 months of embedment. This advantage of slag mortar is explained by a high electrical resistivity with respect to OPC mortars, determined by electrochemical impedance spectroscopy.Finite element simulations are performed using Cast3m software on meso-scale in order to evaluate the mechanical effect of the corrosion layer development on the surrounding matrix. The corrosion kinetics of the alloy, the nature of corrosion products and their mechanical properties identified using SEM/EDS and nano-indentation techniques are implemented. The calculations indicate low stress generation in the alkali-activated mortar

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Schaal, Emmanuel. "Comportement en corrosion de matériaux métalliques commerciaux et modèles dans des conditions types UVEOM." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0192/document.

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La corrosion des échangeurs de chaleur est un problème économique et technique majeur des Unités de Valorisation Energétique de Ordures Ménagères (UVEOM). Elle est causée par l’action combinée (i) des gaz de combustion contenant notamment HCl et SO2 et (ii) des cendres riches en chlorures et sulfates alcalins, et sels de métaux lourds. Les travaux présentés dans ce mémoire s’inscrivent dans le projet ANR SCAPAC (n°11-RMNP-0016) et portent sur l’influence des paramètres expérimentaux (température, teneur en chlorures dans les cendres, présence de gaz corrosifs et présence de chlorures de métaux lourds dans les cendres) sur la tenue à la corrosion de deux alliages utilisés en milieu UVEOM : l’acier 16Mo3 et l’alliage base nickel Inconel 625. Ces travaux ont permis de mettre en évidence que la présence de phases fondues, l’augmentation de la teneur en chlorures, la présence de 10% en masse de ZnCl2 dans les mélanges de cendres et la présence de gaz corrosifs (HCl, SO2) dans l’atmosphère sont trois facteurs qui ont induit une corrosion plus importante sur les matériaux, de manière plus prononcée sur l’alliage base fer. Une autre partie du travail s’est focalisée sur l’influence des éléments d’alliage Fe, Cr et Mo. Des alliages « modèles » dont les compositions oscillent autour de la composition de l’alliage Inconel 625 commercial ont été synthétisés par fusion haute fréquence et leur tenue à la corrosion a été évaluée sous air et sous atmosphère corrosive. La bonne optimisation de l’alliage commercial a ainsi été démontrée sous air. Sous atmosphère gaz corrosifs, une teneur en chrome supérieure à 22% massique s’est montrée indispensable à la bonne tenue de l’alliage
Corrosion of heat exchangers is an economic and technical issue in Waste-to-energy plants. It is caused by the combined action of (i) flue gas containing HCl and SO2 and (ii) chlorides and alkali sulfates rich ash. This work is part of the ANR project SCAPAC (supported by the ANR-11-RMNP 0016) and focused on the influence of experimental parameters on the corrosion behavior of two commercial alloys used in Waste-to-Energy plants: the 16Mo3 steel and the nickel-based alloy Inconel 625. This study allowed to highlight that the presence of molten phase, the increase in the chloride content, the presence of 10% by weight of ZnCl2 in the ash mixtures and the presence of corrosive gases (HCl, SO2) in the atmosphere are three factors that have induced an higher corrosion of materials, more pronounced on the iron alloy base. Another part of the work has been focused on the influence of alloying elements Fe, Cr and Mo. Thus, model alloys with compositions oscillating around the composition of Inconel 625 commercial alloy were synthesized by high frequency induction and their corrosion resistance was evaluated in air and in corrosive atmosphere. Good optimization of the commercial alloy has been demonstrated in air. In corrosive atmosphere, a minimum chromium content was required to obtain a good corrosion resistance

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Moradian, Farzad. "Effects of Reduced-Bed Temperature on Volatilization of Inorganic Components during Combustion of Municipal Solid Wastes in Fluidized Bed Boilers." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-19803.

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30

Sassi, Mouna. "Réactivité à haute température de l’hexa-aluminate de calcium au contact des cendres de biomasse." Thesis, Orléans, 2019. http://www.theses.fr/2019ORLE3101.

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La corrosion à haute température par les alcalins (sels ou oxydes de sodium et/ou de potassium à l'état solide, liquide et en état vapeur) et les oxydes liquides (laitiers) est un problème sérieux qui affecte la vie des matériaux réfractaires utilisés dans les installations d'incinération de déchets. Afin de contribuer à une meilleure connaissance de cette attaque, une étude en laboratoire a été réalisée pour étudier la corrosion alcaline de différentes matières premières : chamotte d’argile, andalousite, andalousite mullitisée, mullite, zircone mullite, bauxite, corindon blanc, alumine-β et comparé à l'hexa-aluminate de chaux. La réactivité de l'hexa-aluminate de chaux et de l'alumine avec les laitiers CaO-SiO2 et CaO-Al2O3 est étudiée pour évaluer leur résistance. La cinétique de réaction est déterminée à partir d'essais de corrosion ex situ par DRX après refroidissement, sur des grains de CA6/Al2O3 mélangés à des laitiers synthétisées et broyées dans des proportions variables. Pour les grains d'alumine et d'hexa-aluminate de chaux, la dissolution est rapide, suivie d'une lente précipitation d'un composé intermédiaire. Ceci est en accord avec les prévisions thermodynamiques. Par conséquent, l'hexa-aluminate de chaux présente à la fois une stabilité thermochimique élevée au contact des alcalins et une résistance élevée à la dissolution des oxydes liquides. Des essais industriels ont été réalisés dans un incinérateur de déchets dangereux situé à Houston, USA. Les résultats après une période d’essai de 7.5 mois montrent que le béton d’hexa-aluminate de chaux résiste bien
High-temperature corrosion by alkali (salts or oxides of sodium and/or potassium in solid, liquid, and vapor state) and slag is a serious problem that affects the service life of refractories used in incineration plants. In order to contribute to a better knowledge of this attack, a laboratory study was carried out during this research to study alkali corrosion of different raw materials: fireclay, andalusite, mullitized andalusite, mullite, fused zirconia mullite, bauxite, white corundum, β-alumina and compared to calcium hexa-aluminate.Moreover, the reactivity of calcium hexa-aluminate and alumina with CaO-SiO2 and CaO-Al2O3 slags is studied to evaluate their resistance. The reaction kinetics is determined from ex-situ corrosion tests by XRD after cooling, on CA6/Al2O3 grains mixed with slag synthesized and milled in varying proportions. For both alumina and calcium hexa-aluminate grains, the dissolution is fast, followed by a slow precipitation of an intermediate compound. This is in agreement with thermodynamic predictions.As a result, calcium hexa-aluminate shows both high thermochemical stability in contact with alkali and high dissolution resistance to liquid oxides. Industrial trials are underway in an American hazardous waste incinerator located in Houston. The results after a trial period of 7.5 months show that calcium hexaluminate castable is resistant

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31

Chou, Shih-Peir, and 周世培. "Corrosion Inhibition of Carbon Steel in Alkaline Solutions Containing Hydrogen Sulfide and Cyanide." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/87715741057965511490.

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碩士
國立中央大學
機械工程學系
84
The article used DC polaration and AC impendence to discuss (1)The institudeof corrosional elechemical mechanism on carbon steel in the environment ofH2S/NH3/CN- and H2S/NH3/ CN-/Cl-.(2)By means of the analysis of reaction institude,find out the reasons that lead to the corrosional factor,and selectproper inhibitors to control .The abstract is as following:1.The analysis ofcorrosional institude:In the alkaline environment of H2S,the corrosion rateof system increases as the concentration of CN- and pH values increase.And theopen circual potention moves in the ative diretion,and the anodic nose of Tafelpolarational curve is more obvious.If there exists Cl- in the system,the carbonsteel will be pitted,and the phonoment of pitting increases as the concentration of Cl- increases.2.The effect of inhibitors:a.commerical inhibitors:Afteradding the four kinds of inhibitors,A,B,C,D,the inhibitive efficiency can reach85%,so A,B,C,D,are called inhibitors of competitive absorption type;after adding seven inhibitors ,E,F,G,H,I,J,K,the effect of orrosion will be worse,so E,F,G,H,I,J,K,are called inhibitors of common absorption type.b.singal inhibitors: Comparing with the inhibitors of three sevies,NH2-CS-R,NH2-CO-R, R-(CH2CH2OH)x,the R-(CH2H2OH)x sevie has better effect of inhibitive.In the inhibitor ofR-(CH2CH2OH)x,the effect of inhibitive effeciency of all systems become worseas the concentration of inhibitor lowers down and the temperature of environment lifts up,and the absorption on carbon steel belongs to typical Langmuir isothermal absorption,and the order of active energy of all systems is :MDEA>MEA>DEA>TEA.In comparison with NH2-CS-R and NH2-CO-R,the inhibitive efficienychanges as R changes,and its order is:(-NH2)>(-CH3)>(-NHNH2)>(-C6H5),in thecondition of the same R ,comparing the influene of >S= and >O=,we discover thatthe inhibitive efficieny of >S= is better.

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32

Deng, Zi-Ping, and 鄧子平. "Corrosion Inhibition of N,S-heterocyclic compounds in the alkaline cleaning of the boiler." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/32079057802471504914.

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Liu, Po-yi, and 劉柏邑. "Study on the anti-Alkaline-corrosion property of aluminum coated with Hydrotalcite/polymer composites." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/92414289436302888961.

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碩士
國立高雄大學
應用化學系碩士班
101
The present study intends to one step hydrothermal synthesis method, a dense and continuous hydrotalcite (Layered Double Hydroxide, LDH) alkaline material film was prepared on an aluminum plate. Hydrotalcite is a layered inorganic material, has high-temperature characteristics, the interlayer can be further polymer modified, the formation of inorganic/organic nanocomposite materials, by using polymercharacteristics of non-conductive and more preventing an acid and alkalianto perform plug hole, hopecan segregate the water and other corrosive factors penetrate hydrotalcite to enhance corrosion resistance. First use hydrothermal Synthesis of hydrotalcitefilm, and use electrochemical to perform corrosion tests in different pH environment. Then use anionic surfactants at the membrane to improve interlayer distance and placed into polymer monomer to heat polymerization methodto form a composite material, identified by XRD, FTIR and SEM analysis, and use of the TGA test the thermal properties, observe the the polymer pyrolysis temperature can be improved under the hydrotalciteprotection, the ultimate the way byelectrochemical in an alkaline environment for corrosion tests, and compared with the before modifiedhydrotalcite performance .

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34

Premlall, Kasturie. "Effect of laser surface irradiation on the corrosion behaviour of mild steel in an alkaline environment." 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000557.

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M. Tech. Chemical Engineering.
Discusses the corrosion of mild steel due to sulphate ions together with chloride ions in concrete reinforcement in alkaline media can be limited or even eliminated by the introduction of laser surface irradiation on the mild steel material.

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35

Liao, Hsueh-Lung, and 廖學隆. "Electrochemical Behavior on the Stress Corrosion Cracking of High Strength AA7050 Aluminum Alloy in Alkaline 3.5%NaCl Solution." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/09339897181115068930.

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Jeng, Yi-Fan, and 鄭逸凡. "Properties of High Performance Concrete Containing Nano-silica Powder under the corrosion of Strong Acid and Alkali." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/01921129095595495565.

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碩士
國立高雄應用科技大學
土木工程與防災科技研究所
94
The concrete structures in chemical factories are often attacked by acid and alkali. This may cause the deterioration of concrete, decrease of the survival of structures and increase of the cost of maintenance. The purpose of this research is to investigate the properties of High Performance Concrete Containing Nano-silica Powder (NSHPC) under the corrosion of acid and alkali. In the first part of this disertation, we regulate the paste amount of concrete (n=1.3); the parameters are Water-binder ratio (W/B=0.24, 0.31 and 0.38) and varying content of Nano-silica powder (0% and 2%). Secondly, we regulate the Water-binder ratio (W/B=0.38); the parameters are paste amount (n=1.1, 1.3 and 1.5) and varying content of Nano-silica powder (0% and 2%). We also compare with Ordinary Portland Concrete (OPC, the design strength is 350 Kg/cm2). The test included Rapid resistance of acid and alkali, compressive strength, ultrasonic wave propagation velocity measurement, electrical resistivity, rapid chloride ion penetration test and Field emission scanning electron microscope (FE-SEM). The results show that the less of the Water-binder ratio and paste amount of High Performance Concrete (HPC) will make the better mechanical properties, low permeability, higher electrical resistivity and better anti-corrosion ability; while the anti-corrosion ability of OPC is bad. The adding of Nano-silica powder in HPC will raise the workability and anti-corrosion ability of HPC more effectively. After the hydration of Nano-silica powder, it will form Calcium Silicate Hydrate (C-S-H) gel and fill concrete pore making concrete densified. Namely, NSHPC owns fine anti-corrosion ability under acid and alkali attack.

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Wang, Sih-Ying, and 王思穎. "A Study on Stress Corrosion Crack for Biodegradable Mg-5wt.%Sn Alloy by Equal Channel Angular Extrusion and Alkali Treatment in Simulated Body Fluids." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/n55n4y.

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碩士
國立交通大學
材料科學與工程學系所
105
In this study, biodegradable Mg-5wt.%Sn alloy showed different microstructure after Equal Channel Angular Extrusion (ECAE). In addition, a protective layer can be formed on the surface of Mg-5wt.%Sn alloy via alkali treatment. We observed the stress corrosion crack of Mg-5wt.%Sn alloy after ECAE and alkali treatment in simulated body fluid (SBF) by 3-point bending test. The results indicated that ECAE process can effectively refine the grain by dynamic recrystallization. After two and four ECAE passes, the average grain size of Mg-5wt.%Sn alloy can be refined from 135.9 µm to 47.9 µm and 18.4 µm, respectively. At the same time, more Mg2Sn phase gradually precipitated on grain boundary from a-Mg matrix due to the effect of time and temperature. Both depth and length of stress corrosion crack for ECAE processed Mg-5wt.%Sn alloy in SBF are short and tend to show a uniform corrosion behavior. Since the route of stress corrosion crack of Mg-5wt.%Sn was intergranular type, grain refinement can extend the crack propagation route and inhibit the crack propagation rate. Besides, small grain sizes allow the second phase become a corrosion barrier, and increase corrosion resistance to some extent. Alkali treatment can form a Mg(OH)2 protective layer on the surface of Mg-5wt.%Sn alloy, and the corrosion can be postponed. Mg-5wt.%Sn alloy after four passes ECAE and alkali treatment existed a more compact protective layer and showed best stress corrosion resistance. Grain refinement may help compensate for oxide/magnesium mismatch and enhance the passivity of the protective layer. The stress corrosion product of Mg-5wt.%Sn alloy in SBF is mainly Mg(OH)2, CaCO3 and Ca3Mg3(PO4)4, indicating a good biocompatibility.

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Garcia, Anthony Michael. "Durability testing of rapid, cement-based repair materials for transportation structures." Thesis, 2014. http://hdl.handle.net/2152/26511.

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For repairing concrete transportation infrastructure, such as pavements and bridges, much importance is placed on early-age strength gain as this has a major impact on scheduling and opening to traffic. However, the long-term performance and durability of such repair materials are often not satisfactory, thus resulting in future repairs. This research project focuses on the evaluation of the durability of various rapid-setting cementitious materials. The binders studied in this project include calcium aluminate cement (CAC), calcium sulfoaluminate cement (CSA), Type III portland cement, alkali-activated fly ash (AAFA) , and various prepackaged concrete materials. In addition, selected CAC and CSA mixtures were further modified with the use of a styrene-butadiene latex. The durability aspects studied include freezing-and-thawing damage and the implications of air entrainment in these systems, alkali-silica reaction, sulfate attack, and permeability of the concrete matrix and potential corrosion.
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