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Paritong, Hilke. "Development of corrosion resistant niobium-based PVD coatings." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/20185/.
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Niobium is well known for its excellent corrosion resistance based on the formation of a stable passive oxide layer, which protects the metal against corrosion in most aqueous media and makes it an interesting candidate for corrosion resistant coating applications. However, deposition of Nb films is restricted to few technologies and difficulties arise from the toxic nature of the electrolytes employed in electrodeposition of Nb, the high reactivity of the metal with residual gases in vacuum plasma spraying and its high melting point (Tm = 2500 0C) in PVD deposition. The present thesis describes the development of corrosion resistant Nb coatings on stainless steel and brass substrates by the combined steered arc/unbalanced magnetron sputtering technique. Evaluation of the corrosion behaviour is performed by potentiodynamic polarisation measurements in 3% NaCl. It is shown that corrosion resistant Nb coatings, with passivation characteristics similar to that of bulk Nb, can be produced on stainless steel substrates by unbalanced magnetron sputtering at a low deposition temperature (T = 250 0C) under reduced ion bombardment. However, the ion etching pre-treatment of the substrate prior to deposition has a significant influence on the corrosion resistance of the coating/substrate system. The employed polarisation measurements reveal that a fully passive and protective behaviour could only be achieved if Nb ions from the cathodic arc source are chosen as the etching species. In contrast, coatings deposited after Cr ion etching from the arc source and inert Ar ion etching, utilising a glow discharge, exhibit localised breakdown and pitting of the substrate. Cross sectional TEM imaging and STEM-EDX analyses reveal that bombardment of the stainless steel substrate by the multiply charged Nb ions generates a compositionally intermixed, very fine crystalline or "amorphised" interface layer, with a thickness of ~3-8nm, depending on the Nb ion energy. It is proposed that this layer acts as an additional barrier against corrosion due to (i) the structural homogeneity achieved by amorphisation and (ii) chemical stabilisation due to the introduction of Nb in the near surface region. The energy of the bombarding Nb ions, i.e. the substrate bias voltage during the etching stage, was found to further influence the corrosion resistance. Best results are achieved with "medium" bias voltages in the range of -600V to -800V, which is believed to be due to an optimum combination of structural and chemical protection mechanisms. The fully passive corrosion behaviour could not be observed in the case of brass substrates. However, the PVD coating systems on brass and on stainless steel are superior, in the employed polarisation measurements, to commercially produced, electroplated Cr, Ni and Ni/Cr coatings on the same substrate materials. Other coating properties investigated in the present study include microstructure, hardness, crystallographic orientation and residual film stresses.
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Lawal, Josephine. "Physical vapour deposition of aluminium-rich nanostructured/amorphous metallic coatings for wear and corrosion protection." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18364/.
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This research is aimed at designing and depositing multi-functional aluminium-based Physical Vapour Deposition (PVD) coatings that can serve as a protection for light alloys, non-ferrous alloys and low alloy steels against wear and corrosion. Coatings deposition was achieved by exploring the capabilities an environmentally-friendly plasma-assisted PVD process (i.e. closed-field unbalanced magnetron sputtering method). Three deposition sequences (series 1, 2 and 3) were undertaken, using two different target configurations, in an argon or argon/nitrogen atmosphere. A wide range of coatings compositions was deposited on commonly used engineering alloy substrates (i.e. austenitic stainless steel, AISI 304; low alloy steel, AISI 4145 and high speed steel, AISI M2), as well as silicon wafer. A variety of coatings characterisations were carried out; these include: Scanning and Transmission Electron Microscopy (SEM/TEM), Focussed Ion Beam microscopy (FIB), optical microscopy, X-Ray Diffraction (XRD), Energy-Dispersive X-ray analysis (EDX) and Glow Discharge Optical Emission Spectrometry (GDOES). The International Centre for Diffraction Data (ICDD) PDF-4+/SIeve+ phase identification database and digital pattern simulation tool was demonstrated to be useful for phase identification and was also extended to crystallite size estimation. Nanoindentation and micro-hole drilling tests were carried out to assess coating mechanical properties. Coating tribological properties were evaluated by reciprocating-sliding and slurry micro-abrasion wear tests. The responses (in terms of open circuit potential (OCP) and potentiodynamic polarisation behaviour) of coatings to a neutral salt corrosive environment were also recorded. In addition, annealing was used to establish coatings thermal stability, as well as the possibility of producing nanostructured coatings by promoting devitrification in completely amorphous coatings (as deposited). A mathematical approach for analysing experimental results and predicting coating properties has also been proposed. Lightly-stressed, partially nanocrystalline and completely amorphous coatings (with a wide range of chemical compositions) were deposited. The thickness of coatings in the main deposition sequence (series 2) ranged from approximately 7 to 14 μm. Coatings showed relatively high hardness (ranging from 8 to 17 GPa) and low modulus (< 200 GPa) – matching closely the modulus of commonly used steel substrates (e.g. stainless steel). Excellent tribological properties, especially in terms of resistance to abrasion (comparable to those of common PVD ceramic coatings like CrN) were achieved. Coatings also possessed a wide range of corrosion properties, with OCP values between -0.3 and -0.6 V. Most of the coatings remained thermodynamically stable up to 600ᵒC. Results of various correlation analyses (and structural similarities of corresponding coatings in different deposition sequences) illustrate the reproducibility of the AlNiTiSiB(N) coatings deposited. The AlNiTiSiB(N) coatings presented in this Thesis are environmentally-benign and can be used in many engineering applications especially where there are concerns about simultaneous wear and corrosion attacks of the underlying metal substrate. The coatings can also be utilised for oxidation resistance in moderately high-temperature applications.
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Thurber, Casey Ray. "Electrodeposited Metal Matrix Composites for Enhanced Corrosion Protection and Mechanical Properties." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849736/.
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In the oil and gas industry, high corrosion resistance and hardness are needed to extend the lifetime of the coatings due to exposure to high stress and salt environments. Electrodeposition has become a favorable technique in synthesizing coatings because of low cost, convenience, and the ability to work at low temperatures. Electrodeposition of metal matrix composites has become popular for enhanced corrosion resistance and hardness in the oil and gas industry because of the major problems that persist with corrosion. Two major alloys of copper-nickel, 90-10 and 70-30, were evaluated for microbial corrosion protection in marine environments on a stainless steel substrate. Copper and copper alloys are commonly used in marine environments to resist biofouling of materials by inhibiting microbial growth. Literature surveying the electrodeposition of Cu-Ni incorporated with nano- to micro- particles to produce metal matrix composites has been reviewed. Also, a novel flow cell design for the enhanced deposition of metal matrix composites was examined to obtain the optimal oriented structure of the layered silicates in the metal matrix. With the addition of montmorillonite into the Ni and Cu-Ni matrix, an increase in strength, adhesion, wear and fracture toughness of the coating occurs, which leads to an increase corrosion resistance and longevity of the coating. These coatings were evaluated for composition and corrosion using many different types of instrumental and electrochemical techniques. The overall corrosion resistance and mechanical properties were improved with the composite films in comparison to the pure metals, which proves to be advantageous for many economic sectors including the oil and gas industry.
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Day, Kent Allen. "The use of thin polymeric coatings to prevent fretting corrosion and metallic contact in steel-on-steel systems." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/76040.
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A fundamental study was conducted to investigate the ability of thin polymeric coatings to prevent metallic contact and fretting corrosion in steel-on-steel systems. Ten polymer types were chosen for study: polymethylmethacrylate (PMMA), polytetrafluoroethylene (PTFE), polyimide (PI), polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), low-density polyethylene (LOPE), high-density polyethylene (HDPE), polysulfone (PSO) and polystyrene (PS). These polymers were applied as thin films to a steel disk which was in turn fretted by a normally-loaded steel sphere.
The experimental investigation consisted of two phases. In the first phase, the lives of the ten polymer types were evaluated over a range of normal loads from 11.1 to 44.5 N. In the second phase, optical and electron microscopy were used to document the fretting process at the sphere-film interface as a function of time.Master of Science
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Saillard, Audric. "Modeling and simulation of stress-induced non-uniform oxide scale growth during high-temperature oxidation of metallic alloys." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33898.
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The metallic alloys employed in oxidizing environment at high temperature rely on the development of a protective oxide scale to sustain the long-term aggressive exposition. However, the oxide scale growth is most of the time coupled with stress and morphological developments limiting its lifetime and then jeopardizing the metallic component reliability. In this study, a mechanism of local stress effect on the oxidation kinetics at the metal/oxide interface is investigated. The objective is to improve the understanding on the possible interactions between stress generation and non-uniform oxide scale growth, which might result in a precipitated mechanical failure of the system. Two different oxides are studied, alumina and chromia, in two different industrial systems, thermal barrier coatings and solid oxide fuel cell interconnects. A specific thermodynamic treatment of local oxide phase growth coupled with stress generation is developed. The formulation is completed with a phenomenological macroscopic framework and a numerical simulation tool is developed allowing for realistic analyses. Two practical situations are simulated and analyzed, concerning an SOFC interconnect and a thermal barrier coating system, for which oxide scale growth and associated stress and morphological developments are critical. The consequence of the non-uniform oxide growth on the system resistance to mechanical failure is investigated. Finally, the influences of material-related properties are studied, providing optimization directions for the design of metallic alloys which would improve the mechanical lifetime of the considered systems.
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Crossen, Jonathan David. "Adhesion of organic coatings and corrosion protection." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361892.
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Lee, David Tsu-Long. "Behaviour of corrosion-protection coatings in light alloys." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:bfbcec97-5f42-4eb3-aaec-ba5443e953ba.
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Anionic chromate (VI) compounds are inhibitive pigments and have been effectively incorporated into organic coatings to protect metal surfaces from aggressive ions, but their risk as a human carcinogen and being harmful to the environment has led to the search of suitable alternatives. Aluminium alloy, AA2024-T3, is the substrate metal alloy used in the experiments and can be found in aircraft fuselage structures due to their high strength-to-weight ratio. However, the presence of intermetallic particles increases susceptibility to localised corrosion. To investigate the protection mechanisms of primers on light alloys, many different factors must be taken into account; from aluminium alloy corrosion processes, the effects of intermetallic additions to coating chemistry, morphology and inhibitive pigments. The chemical environment in which the samples are tested in will also affect the corrosion mechanisms of the alloy as well as the performance of the coatings and release of pigments. It will be important to consider which factors are operating under particular conditions so that experimental results can then be best interpreted. As part of this project, potentiodynamic polarisation, electrochemical impedance spectroscopy and electrochemical noise analysis have been used to investigate the protective mechanisms in which chromate-based paints protect against corrosion and UV-Visible spectroscopy, scanning acoustic microscopy and optical microscopy have been used to investigate pigment release mechanism to identify what characteristics are important when developing new primers.
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ZHANG, CHENG. "PIGMENTED POLYURETHANE/POLYSILOXANE HYBRID COATINGS FOR CORROSION PROTECTION." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1495381409246105.
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Bingham, Ruth. "Corrosion protection and self-healing in nanocomposite coatings." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/corrosion-protection-and-selfhealing-in-nanocomposite-coatings(d1419ee3-a028-401a-80c2-2151f7f1f633).html.
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Recent interest in environmentally friendly alternatives to chromate-based corrosion inhibitors has led to the development of a range of novel coating formulations. The work described in this thesis has been aimed at investigating the mechanism of self-healing and active corrosion protection of the new coatings by searching for active components that have migrated from the coating to a controlled defect. The use of glow discharge optical emission spectroscopy (GDOES) has been investigated as a tool for both the generation of a reproducible controlled defect and for elemental depth profiling of the coatings and corroded substrates. Conclusions drawn from the elemental depth profiles have been validated by a range of characterisation techniques including optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX) and electrochemical techniques. The work has focused particularly on a comparison of hybrid coatings doped with inhibitors encapsulated in nano-containers, as compared with the direct addition of inhibitor species to the coating matrix. The work also investigates the effects of inhibitor addition to sol-gel coatings or primer systems or both, highlighting possible synergistic effects of mixed inhibitor systems (for example, sol-gel coating doped with strontium aluminium polyphosphate (SAPP)) supporting primers doped with benzotriazol (BZT) or mercaptobenzothiazol (MBT). The various coatings have also been studied in the absence of inhibitor species to assess the effectiveness of the coatings as barriers between the substrate and the corrosive environment. This aspect of the study has highlighted minor inhibitive effects of some of the reagents used in the coating formulations and a major inhibitive effect of the nano-containers. The work therefore concludes with recommendations for a possible coating formulation combining the most beneficial elements of the various coatings investigated.
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Yasakau, Kiryl. "Active corrosion protection of AA2024 by sol-gel coatings with corrosion inhibitors." Doctoral thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/3724.
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Doutoramento em Ciência e Engenharia de MateriaisA indústria aeronáutica utiliza ligas de alumínio de alta resistência para o fabrico dos elementos estruturais dos aviões. As ligas usadas possuem excelentes propriedades mecânicas mas apresentam simultaneamente uma grande tendência para a corrosão. Por esta razão essas ligas necessitam de protecção anticorrosiva eficaz para poderem ser utilizadas com segurança. Até à data, os sistemas anticorrosivos mais eficazes para ligas de alumínio contêm crómio hexavalente na sua composição, sejam pré-tratamentos, camadas de conversão ou pigmentos anticorrosivos. O reconhecimento dos efeitos carcinogénicos do crómio hexavalente levou ao aparecimento de legislação banindo o uso desta forma de crómio pela indústria. Esta decisão trouxe a necessidade de encontrar alternativas ambientalmente inócuas mas igualmente eficazes. O principal objectivo do presente trabalho é o desenvolvimento de prétratamentos anticorrosivos activos para a liga de alumínio 2024, baseados em revestimentos híbridos produzidos pelo método sol-gel. Estes revestimentos deverão possuir boa aderência ao substrato metálico, boas propriedades barreira e capacidade anticorrosiva activa. A protecção activa pode ser alcançada através da incorporação de inibidores anticorrosivos no prétratamento. O objectivo foi atingido através de uma sucessão de etapas. Primeiro investigou-se em detalhe a corrosão localizada (por picada) da liga de alumínio 2024. Os resultados obtidos permitiram uma melhor compreensão da susceptibilidade desta liga a processos de corrosão localizada. Estudaram-se também vários possíveis inibidores de corrosão usando técnicas electroquímicas e microestruturais. Numa segunda etapa desenvolveram-se revestimentos anticorrosivos híbridos orgânico-inorgânico baseados no método sol-gel. Compostos derivados de titania e zirconia foram combinados com siloxanos organofuncionais a fim de obter-se boa aderência entre o revestimento e o substrato metálico assim como boas propriedades barreira. Testes industriais mostraram que estes novos revestimentos são compatíveis com os esquemas de pintura convencionais actualmente em uso. A estabilidade e o prazo de validade das formulações foram optimizados modificando a temperatura de armazenamento e a quantidade de água usada durante a síntese. As formulações sol-gel foram dopadas com os inibidores seleccionados durante a primeira etapa e as propriedades anticorrosivas passivas e activas dos revestimentos obtidos foram estudadas numa terceira etapa do trabalho. Os resultados comprovam a influência dos inibidores nas propriedades anticorrosivas dos revestimentos sol-gel. Em alguns casos a acção activa dos inibidores combinou-se com a protecção passiva dada pelo revestimento mas noutros casos terá ocorrido interacção química entre o inibidor e a matriz de sol-gel, de onde resultou a perda de propriedades protectoras do sistema combinado. Atendendo aos problemas provocados pela adição directa dos inibidores na formulação sol-gel procurou-se, numa quarta etapa, formas alternativas de incorporação. Na primeira, produziu-se uma camada de titania nanoporosa na superfície da liga metálica que serviu de reservatório para os inibidores. O revestimento sol-gel foi aplicado por cima da camada nanoporosa. Os inibidores armazenados nos poros actuam quando o substrato fica exposto ao ambiente agressivo. Numa segunda, os inibidores foram armazenados em nano-reservatórios de sílica ou em nanoargilas (halloysite), os quais foram revestidos por polielectrólitos montados camada a camada. A terceira alternativa consistiu no uso de nano-fios de molibdato de cério amorfo como inibidores anticorrosivos nanoparticulados. Os nano-reservatórios foram incorporados durante a síntese do sol-gel. Qualquer das abordagens permitiu eliminar o efeito negativo do inibidor sobre a estabilidade da matriz do sol-gel. Os revestimentos sol-gel desenvolvidos neste trabalho apresentaram protecção anticorrosiva activa e capacidade de auto-reparação. Os resultados obtidos mostraram o elevado potencial destes revestimentos para a protecção anticorrosiva da liga de alumínio 2024.
The aerospace industry employs high strength aluminum alloys as a constructional material for aircrafts. Aluminum alloys possess advanced mechanical requirements, though suffer from corrosion. Therefore, corrosion protection is always used for aluminum alloys. Up to now the most effective corrosion protection systems include chromium (VI) as the main constituent of pretreatments and corrosion inhibitive pigments. However, the chromates are strongly carcinogenic and the present health regulations banned the use of Cr (VI) containing materials in industry. Consequently, there is a need for environmentally safe corrosion protection systems. The main objective of the present work is the development of active anticorrosion pre-treatments for 2024 aluminum alloy on the basis of hybrid sol-gel layers. The effective corrosion pre-treatment should confer adequate adhesion together with good barrier properties and active corrosion protection ability. The active corrosion protection can be achieved by introducing the corrosion inhibitors in the pre-treatment. Successful fulfilment of the main objective required accomplishing of different stages of the work. At first the localized corrosion of AA2024 was investigated in detail. The obtained results provide better understanding of the intimate aspects of the corrosion susceptibility of AA2024. Different prospective corrosion inhibitors were investigated using electrochemical and microstructural methods. At the second stage the development of hybrid sol-gel coatings was performed. Titania and zirconia based derivatives were combined with organofunctional silanes in order to provide the enhanced adhesion between the metal and the coating and to confer good barrier properties. Industrial tests show that the developed sol-gel coatings are compatible with common organic protection systems. The stability and life time of the sol-gel formulations were also optimized by changing the storage temperature and the amount of water during the synthesis. Sol-gel systems were doped with the selected corrosion inhibitors and studied from the point of view of passive and active corrosion protective properties at the third stage of the work. The results demonstrate the influence of the inhibitive additives on the corrosion performance of the sol-gel coatings. Some inhibitors can provide active corrosion protection in combination with the sol-gel coating, but some chemically interact with the sol-gel matrix resulting in failure of the protective properties of coatings. New approaches of inhibitor incorporation and delivery were used in the fourth stage of the work due to problems associated with the direct introduction of inhibitors in the sol-gels. A nanoporous titania-based pre-layer applied directly to the alloy was employed for storage and release of inhibitors. Nanocontainers of corrosion inhibitors based on silica and halloysite nanoclay with Layer-by- Layer assembled polyelectrolyte shells were used in the second approach. Amorphous cerium molybdate nanowires have been used as corrosion inhibitor nanoparticles in the third approach. During the sol-gel synthesis these nanocontainers were added to impart active corrosion protective properties of the sol-gel coatings. Using these approaches the negative effect of inhibitor on the sol-gel matrix stability was eliminated. The developed sol-gel pretreatments demonstrate important active corrosion protection and self-healing ability. The obtained results show high potential of the developed hybrid sol-gel pretreatment doped with corrosion inhibitors for the corrosion protection of AA2024.
FCT; FSE - SFRH/BD/25469/2005
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Balaskas, Andronikos. "Corrosion protection by encapsulated inhibitors." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/corrosion-protection-by-encapsulated-inhibitors(6295df0b-7ae9-4e8f-957b-2f9468740cb8).html.
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This work, within EPSRC LATEST2 (Light Alloys Towards Environmentally Sustainable Transport 2) Programme Grant, is focused on the development of environmentally-friendly corrosion inhibitors, nanocontainers loaded with inhibitors and epoxy coatings for corrosion protection of the aerospace alloy AA 2024-T3. More specifically, the electrochemical techniques of image assisted electrochemical noise, electrochemical impedance spectroscopy, split-cell technique and potentiodynamic polarization were used for the qualitative and quantitative evaluation and characterization of environmentally-friendly corrosion inhibitors on AA 2024-T3. Scanning electron microscopy observations complemented the electrochemical measurements. It was found that the organic inhibitor 2-mercaptobenzothiazole provides excellent corrosion inhibition properties to AA 2024-T3 in 3.5% sodium chloride solution. Among the tested nitrates, cerium nitrate provides the best inhibition performance. The concentration of the nitrate salt is critical in determining the corrosion protection. An excessive concentration of nitrate ions results in the dissolution of copper-containing oxides, increasing the corrosion rate. Different types of core-shell structured nanocontainers were synthesised with the methods of distillation precipitation polymerization, emulsion polymerization and sol-gel. The nanocontainers were characterized by scanning electron and transmission electron microscopy observations. The corrosion inhibitor 2-mercaptobenzothiazole was encapsulated into the nanocontainers. The encapsulation of 2-mercaptobenzothiazole was evaluated with energy dispersive X-ray analysis mapping micrographs from transmission electron microscopy measurements. Epoxy coatings with nanocontainers loaded with 2-mercaptobenzothiazole were applied on AA 2024-T3 for protection against corrosion. The corrosion protection properties of the coatings were evaluated with electrochemical impedance spectroscopy. The results indicated that epoxy coatings provide excellent barrier properties to AA 2024-T3 in the demanding environment of 3.5% sodium chloride solution with low frequency impedance values more than 1 GOhm cm2 for over 4000 hours of testing. Coatings containing nanocontainers loaded with 2-mercaptobenzothiazole tested with an artificial scribe revealed protection of the AA 2024-T3 substrate in the scribed area, decrease of the anodic delamination in the early hours and decrease number of cathodic dark areas after long immersion time. Overall, epoxy coatings with encapsulated inhibitors can be considered as a promising system for potential replacement of hexavalent chromium treatments on aerospace alloy AA 2024-T3.
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Ejenstam, Lina. "Hydrophobic and superhydrophobic coatings for corrosion protection of steel." Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175405.
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Since metals in general, and steels in particular, are vital construction materials in our modern society, the corrosion protection of said materials is of great importance, both to ensure safety and to reduce costs associated to corrosion. Previously, chromium (VI) and other harmful substances were effectively used to provide corrosion protection to steel, but since their use was heavily regulated around year 2000, no coating has yet been developed that, in a fully satisfactory manner, replaces their corrosion protective properties.In this thesis, the use of hydrophobic and superhydrophobic surface coatings as part of corrosion protective coating systems has been studied. Since the corrosion mechanism relies on the presence of water to take place, the use of a superhydrophobic coating to retard the penetration of water to an underlying metal surface is intuitive. The evaluation of corrosion protective properties of the hydrophobic and superhydrophobic surfaces was performed using mainly contact angle measurements and electrochemical measurements in severely corrosive 3 wt% NaCl water solution.First, the differences in corrosion protection achieved when employing different hydrophobic wetting states were investigated using a model alkyl ketene dimer wax system. It was found that superhydrophobicity in the Lotus state is superior to the other states, when considering fairly short immersion times of less than ten days. This is due to the continuous air film that can form between such a superhydrophobic surface and the electrolyte, which can retard the transport of electrolyte containing corrosive ions to the metal surface to the point where the electrical circuit is broken. Since corrosion cannot occur unless an electrical current is flowing, this is a very efficient way of suppressing corrosion.An air layer on an immersed superhydrophobic surface is, however, not stable over long time, and to investigate long-term corrosion protection using hydrophobic coatings a polydimethylsiloxane formulation containing hydrophobic silica nanoparticles was developed. This system showed enhancement in corrosion protective properties with increasing particles loads, up until the point where the particle load instead causes the coating to crack (at 40 wt%). The conclusion is that the hydrophobicity of the matrix and filler, in combination with the elongatedivdiffusion path supplied by the addition of particles, enhanced the corrosion protection of the underlying substrate.To further understand how hydrophobicity and particle addition affect the corrosion protective properties of a coating a three layer composite coating system was developed. Using this coating system, consisting of a polyester acrylate base coating, covered by TiO2 particles (with diameter < 100 nm) and finally coated with a thin hexamethyl disiloxane coating, it was found that both hydrophobicity and particles are needed to reach a great enhancement in corrosion protective properties also for this system.Eftersom metaller, och då särskilt stål, är viktigta konstruktionsmaterial i vårt moderna samhälle är korrosionsskydd av stor betydelse, både för att garantera säkerhet och för att minska kostnader som uppkommer i samband med korrosion. Tidigare har sexvärt krom och andra skadliga ämnen använts för att på ett effektivt sätt skydda stål från korrosion, men efter att deras användning kraftigt reglerades runt år 2000 har ännu ingen beläggning utvecklats som helt kan ersätta krombeläggningarna med avseende på funktion.I denna avhandling har hydrofoba och superhydrofoba ytbeläggningar och deras möjliga applikation som en del av ett korrosionsskyddande beläggningssystem studerats. Eftersom korrosionsmekanismen är beroende av närvaron av vatten, är användandet av en superhydrofob beläggning för att fördröja transporten av vatten till den underliggande metallytan intuitiv. De korrosionsskyddande egenskaperna hos superhydrofoba ytbeläggningar utvärderades här främst med hjälp av kontaktvinkelmätningar och elektrokemisk utvärdering i korrosiv lösning bestående av 3 vikts% NaCl i vatten.Först undersöktes skillnaden i korrosionsskydd som uppnås vid användandet av ytbeläggningar med olika hydrofoba vätningsregimer med hjälp av ett modellsystem bestående av ett alkylketendimer vax. Det konstaterades att superhydrofobicitet i Lotusregimen är överlägset bättre än de andra hydrofoba vätningsregimerna, i alla fall när man ser till relativt korta exponeringstider, typiskt mindre än tio dagar. Detta beror på att den kontinuerliga luftfilm som kan bildas på en sådan typ av superhydrofob yta kan minska transporten av elektrolyt (som innehåller korrosiva joner) till metallytan till den grad att den elektriska kretsen bryts. Eftersom korrosion inte kan ske utan en sluten elektrisk krets är detta ett mycket effektivt sätt att förhindra korrosion från att ske.Ett luftskikt på en superhydrofob yta nedsänkt i vatten är dock inte stabilt under lång tid. För att undersöka möjligheten till korrosionsskydd under längre tid med hjälp av hydrofoba beläggningar utvecklades en hydrofob ytbeläggning bestående av polydimetylsiloxan och hydrofoba nanopartiklar av kiseldioxid. Detta system visade en förbättring av korrosionsskyddet vid ökat partikelinnehåll upp till den koncentration (40 wt%) där i stället sprickbildning i ytbeläggningen observerades. Från detta system kunde slutsatsen dras att matrisens och partiklarnasvihydrofobicitet i kombination med den längre diffusionsvägen som partiklarna orsakade förbättrade korrosionsskyddet av den underliggande metallen.För att ytterligare förstå hur hydrofobicitet och partikeltillsatser påverkar en ytbeläggnings korrosionsskyddande egenskaper har dessutom ett treskikts kompositbeläggningssystem utvecklats. Genom att använda detta beläggningssystem, som består av en basbeläggning av polyesterakrylat, ett lager TiO2-partiklar (med en diameter på <100 nm) slutligen belagt med ett tunt ytskikt bestående av hexametyldisiloxan så kunde slutsatsen dras att både en hydrofob matris och partiklar behövs för att nå en markant förbättring av ytbeläggningens korrosionsskyddande egenskaper.
QC 20151015
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Gopalakrishna, Jayashri Sham. "Corrosion protection of advanced surface coatings for decorative applications." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/35042.
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Thesis (PhD) - Swinburne University of Technology, School of Engineering and Science, 2008.A thesis submitted for the degree of Doctor of Philosophy, School of Engineering and Science, Swinburne University of Technology, 2008. Typescript. Includes bibliographical references (p. 189-204).
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Tay, Hwee Koon. "Barrier properties of water-borne polymeric coatings and corrosion protection." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363999.
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Wang, Peng. "Morphology and Protection Mechanisms of Epoxy-silane Anti-Corrosion Coatings." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1246997365.
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Soh, Tedric. "Conductive polymer coating for corrosion protection of steel." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112584.
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There is an increasing interest in exploring the use of conductive polymers for protecting metals from corrosion. The corrosion resistance of steel coated with the conductive polymer polypheneylenevinylene (PPV) is studied. The corrodant used is deaerated 1% w/w NaCl(aq).The PPV coating is deposited by a homemade spinning coater. The effect of substrate microstructure and surface treatment on PPV coating morphology is investigated. The morphology and surface roughness of the coating are measured by Atomic Force Microscopy (AFM). The PPV coating thickness and substrate surface roughness are measured by profilometer.
Open Circuit Potential (OCP), electrochemical impedance spectroscopy (EIS), linear potentiodynamic voltammetry (Tafel) and optical microscopy were used to characterize the structure and properties of the coatings. The correlation between the coating thickness, the surface treatment of the steel substrate prior to coating, and the corrosion behaviour of PPV coated steel was investigated.
Under the condition of our studies, the level of pH in the solution used for corrosion testing has the strongest effect on the corrosion behaviour of PPV coated steel.
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Bahramian, Ahmad. "Enhanced protection of electronic modules : metallic film synthesis and corrosion study." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0550/document.
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Les systèmes Cu /Ni-P/Au sont utilisés comme contacts électriques car ils présentent une conductivité électrique élevée, alliée à un bon comportement mécanique et une résistance à la corrosion. Le Cu possède une conductivité électrique unique qui en a fait le métal le plus utilisé en électronique. Cependant, sa faible résistance à la corrosion nécessite l’application de revêtements protecteurs. Les sous couches de Ni (généralement Ni-P) permettent essentiellement d’éviter la diffusion entre Cu et Au. Enfin, la couche de finition en Au est utilisée pour garantir la durée de vie des contacts électriques. Pour des raisons économiques, ce film de faible épaisseur est poreux, entrainant ainsi un couplage galvanique entre l’Au et le Ni au détriment du nickel. Ainsi ce travail est dédié à l’identification et la mise en œuvre des stratégies visant à améliorer la durée de vie des contacts électriques et plus globalement des modules électroniques.Lors de cette thèse, nous avons développé 3 stratégies : (1) améliorer les propriétés de la couche barrière de Ni, (2) remplacer l’or par un métal moins onéreux, (3) sceller les pores de la couche d’Au les propriétés du film barrière Ni-P améliorées notamment par des additifs tels que la glycine. Sn a également imposé un effet similaire. D’autres couches de finition nobles NiAg et NiPd ont été étudiées. Bien que des films hautement adhésifs aient été formés par potentiel pulsé, ces films poreux n'offraient pas un comportement correct à la corrosion. Enfin, il a été découvert que les pores de la couche de finition en Au peuvent être efficacement scellés par électrodéposition de poly méthacrylate de méthyleCu/Ni(Ni-P)/Au systems are used as electrical contacts due to their combination of electrical conductivity, corrosion resistance, and mechanical behavior. Cu has a unique electrical conductivity that made it the most used metal in electronics. However, protective coatings must be applied on Cu due to its poor corrosion resistance. Au films are used to secure a proper lifetime of electrical contacts. Ni films are essential to avoid the diffusion of Cu into Au. Electrodeposition is the method of choice to form these multi-layer systems. The Au top-coat is notably thin and hence porous. The corrosive media penetrate through these pores, hence electrical contacts are suffering from a galvanic coupling. This work is dedicated to identify and test the strategies to enhance the lifetime of electrical contacts and electronic modules. Three strategies were detected, (1) improve the properties of the Ni barrier layer, (2) replacing the Au film with a thicker but cheaper alternative metal, and (3) seal the pores of Au top-coat using a post-treatment process. It was found out that the properties of the Ni-P barrier film can be notably improved by additives such as glycine. Sn also found to be highly advantageous for forming NiSn barrier coatings. NiAg and NiPd noble top-coats were investigated as alternatives to Au thin films. Although highly adhesive films were formed using the pulse deposition, the films were porous and thus did not offer a proper corrosion behavior. And finally, a cathodic electropolymerization was employed as a post-treatment method. It was found out that the pores of Au top-coat can be effectively sealed by the electrodeposition of polymethyl methacrylate
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COSTA, ISOLDA. "Effect of minor addition elements on the corrosion behaviour of bare and coated steels." reponame:Repositório Institucional do IPEN, 1991. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10281.
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Made available in DSpace on 2014-10-09T12:36:50Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:56:00Z (GMT). No. of bitstreams: 1 04366.pdf: 5734662 bytes, checksum: 226af9141e1984ce9dff1230b5f437ed (MD5)
Tese (Doutoramento)
IPEN/T
University of Manchester, England
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KATARIA, DIPTI L. "POLYANILINE CLAY - POLYIMIDE HYBRID NANOCOMPOSITE COATINGS FOR CORROSION PROTECTION OF AA 2024." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1134153316.
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Mabbutt, S. J. "Investigation into corrosion protection by coatings using the electrochemical noise method." Thesis, University of Northampton, 2000. http://nectar.northampton.ac.uk/2981/.
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The Electrochemical Noise Method (ENM) monitors the small potential and current fluctuations that occur naturally in electrochemical cells. It is the least intrusive of all electrochemical techniques in common use. This work uses the Electrochemical Noise Method to investigate the corrosion protection afforded by organic coatings. A parameter called Noise Resistance (Rn) is derived from an Ohm law relationship using the potential noise (Vn) and current noise (In) values. The noise on the current and potential data sets is calculated as the standard deviation value. The work is divided into three areas. The first looked at coating systems in the intact state on the substrate. In general this part of the work has corroborated previous work where Rn values of >l x 10^7 ohms-cm^2 indicated protection of the substrate, correlating with DC resistance values of the coating. The second area of work investigated scribed coatings on the substrate. An important property of organic anti-corrosive coatings is the ability to protect the substrate at a break in the coating. In the scribed work the level of protection afforded at exposed metal by the coating was related to the Noise Resistance value. The third area of this investigation looked at novel ENM techniques to investigate organic coatings. Detached intact coatings were examined in a “U” tube test cell that can be used to simulate different conditions that may be encountered in service. Also a new technique was devised for obtaining ENM data from corrosion cells, this does not require the two separate substrate elements necessary for the more established methodology. The new technique has been called the Single Substrate (SS) technique to reflect this useful property. The technique could be used for in-situ monitoring of structures and it could be adapted for investigation of other situations such as reinforcement bars in concrete
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Sears, Joanne Marie. "An investigation of aluminium-magnesium-cerium alloy coatings for corrosion protection." Thesis, University of Salford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365974.
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Tu, Khoi. "Enhancing the performance of pulsed current applied coatings for corrosion protection." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/enhancing-the-performance-of-pulsed-current-applied-coatings-for-corrosion-protection(cc494113-792f-4a08-a474-47149b6cedeb).html.
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Accelerated Low Water Corrosion (ALWC) is a particularly severe form of microbiologically induced, aggressive and localised form of corrosion. It is most commonly found just above the Lowest Astronomical Tide. The average corrosion rates are typically very high, about 1.0 mm/wetted side/year, so it should be prevented to ensure the lifetime of steel structures in seawater. In this project, in order to deal with ALWC, a pulsed current applied coating, calcareous film, is studied to form after a sequence of electrochemical treatments to clean the corrosion products and kill bacteria. In sea water, calcareous films (deposits of CaCO3 and Mg(OH)2) are produced on steel structures that are cathodically protected. They have two functions: reducing the current demand from the CP system and acting as a protective coating. When deposition conditions are well controlled, they could provide long-term corrosion protection for steel in sea water. The project aims to understand the fundamentals and mechanism of calcareous deposition under a pulsed current with high current density in a short period. The objectives of the project are to understand calcareous scale growth in a short term under pulsed current and to study the effect of deposition conditions on the properties of the calcareous film. The relationship between deposition time and properties of the deposits has been investigated with different conditions of pulsed current to understand the mechanism of deposition and to identify optimal conditions for deposition. Limiting current densities, potentials and deposition times to prevent loss of deposit and blister formation have also been addressed. In order to show the advantages of pulsed current to control the properties of the deposits, a comparison with properties of the deposits forming under DC is presented. Endurance tests have been performed, using EIS to estimate the long-term performance of the deposits and the mechanism of loss of protection.
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Espartero, Jennifer C. "Polymeric Materials for Corrosion Protection in Geothermal Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1427901218.
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Smith, H. E. M. "The protection of poorly prepared steel surfaces using water-borne coatings." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233531.
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Bhardwaj, Abhinav. "Metallic Encapsulation for High Temperature (>500 °C) Thermal Energy Storage Applications." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5843.
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Deployment of high temperature (>500 °C) thermal energy storage in solar power plants will make solar power more cost competitive and pave the way towards a sustainable future. In this research, a unique metallic encapsulation has been presented for thermal energy storage at high temperatures, capable of operation in aerobic conditions. This goal was achieved by employing low cost materials like carbon steel. The research work presents the unique encapsulation procedure adopted, as well as various coatings evaluated and optimized for corrosion protection. Experimental testing favored the use of 150 μm of nickel on carbon steel for corrosion protection in these conditions. These metallic encapsulations survived several thermal cycles at temperatures from 580 °C to 680 °C with one encapsulation surviving for 1700 thermal cycles.
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ZHU, DANQING. "CORROSION PROTECTION OF METALS BY SILANE SURFACE TREATMENT." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115992852.
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Maqbul, Abdo Ahmed. "An electrochemical study of the corrosion behaviour of metallic coatings on carbon steel strips." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314756.
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Kataria, Dipti. "Polyaniline clay polyimide hybrid nanocomposite coatings for corrosion protection of AA 2024 /." Cincinnati, Ohio : University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1134153316.
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Thesis (M.S.)--University of Cincinnati, 2005.Title from electronic thesis title page (viewed Apr. 21, 2006). Includes abstract. Keywords: Polyaniline, Coatings, Corrosion. Includes bibliographical references.
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Tuaweri, Johnnie T. "Zinc and zinc alloy composite coatings for corrosion protection and wear resistance." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/10888.
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Zinc and its alloys are among the most widely utilised metallic coatings for the sacrificial protection of steel. Although excellent in this mode of protection, these coatings are often less durable when subjected to environments of combined wear and corrosion due to their intrinsic relative softness and ductility. A possible and fast growing way of improving the durability of these coating is by the codeposition of inert particles into the zinc and zinc-alloy matrix. The main aim of this research was therefore to improve the durability of zinc and zinc-nickel coatings by the incorporation of inert particles via electrolytic codeposition methods. The first five chapters of this thesis comprise literature review on the electrodeposition of zinc, its alloys and composite electrodeposition in general. A major part of which was dedicated to the review of various conventional methods and parameters such as current density, agitation, temperature, solution composition, bath additives and pH usually investigated in electrodeposition. The experimental work was principally based on DC electrodeposition and was aimed at understanding the deposition behaviour of zinc and zinc-nickel electrodeposition baths, conditions which influence them and solution compatibility to the introduction of silica particles. A systematic study on the deposition behaviour of both zinc/silica and zinc-nickel/silica composite baths was carried out with particular interest on the rate of particle incorporation and the influence of particles on zinc-nickel alloy deposition. The complimentary codeposition behaviour of the nickel and silica particles was observed. The influence of bath additives such as N,N Dimethyldodecylamine (NND) and sodium nitrate on the rate of silica incorporation was also studied. Both additives were found to improve the rate of particle incorporation for the zinc/silica. The morphologies and compositions of the coatings were analysed with the use of SEM and FEGSEM. Corrosion performance studies were carried out in a neutral salt spray chamber and linear polarisation resistance methods used to determine barrier corrosion properties of the coatings. Anodic polarisation studies were also carried out. The results show an improvement in the corrosion performance of these coatings with the addition of silica particles Reciprocating wear tests were used to determine the wear behaviour of the coatings in terms of weight loss. Improvement in wear resistance was not observed in the zinc/silica coatings probably due to the high content of silica in the coatings. Lower silica contents may be required for the desired improvements. However, there were obvious improvements in the wear behaviour of the zinc-nickel/silica coatings due to the presence of the silica particles.
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Shepherd, Heather. "Application and characterization of polymer coatings for droplet microfluidics and corrosion protection." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1324375641&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Sun, Ming. "Improving corrosion protection of magnesium alloys by plasma electrolytic oxidation based coatings." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/16374/.
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The high susceptibility to corrosion limits the broad application of magnesium alloys, and therefore, the corrosion protection of magnesium is of major concern in practical conditions. A great effort has been made in the last few decades to solve this problem. Various types of surface coatings have been developed to provide corrosion protection for magnesium alloys, among which plasma electrolytic oxidation (PEO) is one of the most promising techniques. The PEO treatment can produce a hard ceramic-like oxide coating on magnesium and its alloys, leading to significantly enhanced wear and corrosion resistance. However, the intrinsic porous morphology of the PEO coatings still limits their effect of corrosion protection. The objective of the present work is to overcome this microstructural drawback, and further improve the corrosion protection ability of PEO coatings on magnesium and its alloys. Different approaches have been adopted to reduce the degradation rate of PEO coatings, including optimisation of the PEO treatment itself, sequential processing combining PEO coating with various post-treatments and formation of smart self-healing PEO coatings inspired by biological systems. The PEO process was investigated by analysing the current/voltage transients, and the PEO coatings were systematically characterised by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FTIR) was also used to study the chemical composition of the plasma enhanced chemical vapour deposition (PECVD) coatings on the PEO coated magnesium alloy. The corrosion resistance of the PEO coatings in 3.5 wt.% NaCl solution was investigated by the electrochemical methods, including open circuit potential (OCP) monitoring, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation scans (PDP). In addition, the mechanical behaviour of PEO coatings was also examined by scratch testing. It was found that both voltage and frequency have significant effect on the properties of PEO coatings, and a more compact coating was produced by pulsed bipolar voltage mode. The PECVD post-treatment was proven to be an effective method of improving the corrosion protection ability if appropriate precursors were used, as this method could cause both positive and negative effects. Coating degradation could also occur during immersion post-treatments, although the corrosion resistance of the PEO coating was also improved by the Ce deposition and benzotriazole (BTA) adsorption. In this case, a better corrosion protection was achieved by combining the PEO coating with Ce-based immersion post-treatment, as the insoluble Ce-containing compounds provided both sealing effect and the inhibition of cathodic reaction. Finally, the self-healing PEO coating incorporated with inhibitor loaded nanocontainers was developed and shown a good potential for providing a long-term corrosion protection for magnesium alloys, even though the corrosion resistance was not significantly increased compared with conventional PEO coating. However, none of the above approaches was perfect, indicating that there is still plenty of work to be done in the future.
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Rogers, Daniel Michael. "INVESTIGATION OF THERMAL SPRAY COATINGS ON AUSTENITIC STAINLESS STEEL SUBSTRATE TO ENHANCE CORROSION PROTECTION." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1651.
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The research is aimed to evaluate thermal spray coatings to address material issues in supercritical and ultra-supercritical Rankine cycles. The primary purpose of the research is to test, evaluate, and eventually implement a coating to improve corrosion resistance and increase efficiency of coal fired power plants. The research is performed as part of a comprehensive project to evaluate the ability of titanium, titanium carbide, or titanium diboride powders to provide fireside corrosion resistance in supercritical and ultra-supercritical steam boilers, specifically, coal driven boilers in Illinois that must utilize high sulfur and high chlorine content coal. [1] The powder coatings that were tested are nano-sized titanium carbide (TiC) and titanium di-boride (TiB2) powders that were synthesized by a patented process at Southern Illinois University. The powders were then sent to Gas Technology Institute in Chicago to coat steel coupons by HVOF (High Velocity Oxy-Fuel) thermal spray technique. The powders were coated on an austenitic 304H stainless steel substrate which is commonly found in high temperature boilers, pipelines, and heat exchangers. The samples then went through various tests for various lengths of time under subcritical, supercritical, and ultra-supercritical conditions. The samples were examined using a scanning electron microscope and x-ray diffraction techniques to study microstructural changes and then determined which coating performed best.
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Ramniceanu, Andrei. "Investigation of parameters governing the corrosion protection efficacy of fusion bonded epoxy coatings." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27848.
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The primary cause of corrosion in transportation structures is due to chlorides which are applied to bridge decks as deicing salts. The direct cost of corrosion damage to the countryâ s infrastructure is approximately $8.3 billion per year. One of the most common corrosion abatement methods in the United States is the barrier protection implemented through the application of fusion bonded epoxy coatings.
The purpose of this study was to investigate various coating and exposure parameters to determine their effects on the corrosion of reinforcing steel. The parameters investigated were: chloride content at the bar depth, coated bar corroded area, corrosion product color under the coating, epoxy coating adhesion, coating color, coating damage (holidays and holes), coating thickness, TGA, DSC and EDS analysis and SEM coating cracking investigation. This was accomplished by testing new coated bar specimens as well as specimens extracted from 27 bridge decks located in Virginia.
This study demonstrated the following: The extracted ECR coating samples presented extensive cracking compared to the new ECR samples in which the coating cracking was limited to only one sample. The DSC results showed that both the extracted samples as well as new samples are not fully cured during the manufacturing process. The coating degree of curing data also showed that the bars are insufficiently and unevenly heated prior to the application of the powder coating. Additionally, the samples investigated presented significant permanent adhesion loss with little or no epoxy coating residue present on the bar surface, while the EDS analysis showed that once adhesion is lost, corrosion will proceed unimpeded under the coating even in the absence of chlorides.
The parameters that presented a direct correlation with the observed corrosion activity were the number of holidays and the number of damaged areas per unit length of bar. This indicates that the passivation of the bare steel exposed to the concrete pore solution at the breaches in the epoxy coating is not the same as a bare bar under similar exposure conditions allowing it instead to corrode at lower concrete chloride concentration levels than bare bars.
The results also show a distinct loss of quality control in the handling and possibly storage of new coated bars. The new ECR samples had significantly higher damage density than the samples extracted from concrete even though the coating is damaged during the placement of the concrete, while there was no change in the number of holidays and cure condition.
Finally, the data presented further evidence that while limited, the non-destructive corrosion assessment methods available for bare steel reinforced structures may also be used on ECR reinforced structures. In particular, the corrosion rate measurements correlated reasonably well with the chloride concentrations at bar level. This indicates that while the chlorides may not influence the corrosion activity under the coating, they do influence the corrosion activity at breaches in the coating.Ph. D.
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Hoffman, John Mark. "Zinc coatings for the external protection of ductile iron water mains." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279981.
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Shah, Kunal G. "Conducting Polymers / Polyimide-Clay Nanocomposite Coatings for Corrosion Protection of AA-2024 Alloy." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1083723910.
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Cross, Samuel R. (Samuel Robert). "Computational modeling and design of multilayer corrosion coatings for galvanic protection of steel." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103269.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 140-146).
Steels represent an economically vital class of alloys for use in structural applications, due to low cost and high strength and toughness, but often suffer from high susceptibility to corrosion in relevant environments. Use of metallic coatings, particularly zinc alloys, has long been a widely employed method for corrosion protection of steel, by acting both as a physical barrier to the aggressive environment, and providing sacrificial protection due to the preferential dissolution of the coating. Recent advances in processing techniques has permitted the efficient deposition of multilayer metallic coatings, which offer tremendous potential for dramatic improvements in performance relative to single layer coatings. However, development of multilayer corrosion coatings is hampered by a number of obstacles, in particular the lack of theoretical or computational tools to predict the corrosion behavior of multilayer coating structures. While existing numerical models for corrosion are well validated for simple geometries and short timescales, there are no models with demonstrated ability to be applied to composite materials such as multilayer coatings, or to incorporate the effects of corrosion damage over time on the effectiveness of the coating. This thesis seeks to address this deficiency through development and validation of two corrosion modeling techniques. The first modeling technique uses standard techniques for numerical modeling of galvanic corrosion to produce time-dependent corrosion simulations for multilayer or compositionally graded coatings, under the assumptions of completely generalized corrosion. The second modeling technique attempts to capture the effect of localized corrosion on multilayer coatings by treating the coating material as a porous electrode with properties calculated through an effective medium approximation. The output of the corrosion models is validated through comparison to a number of quantitative and qualitative corrosion tests on a variety of coatings, and is demonstrated to accurately capture a wide range of phenomena relevant to corrosion of multilayer thin films. Finally, this thesis demonstrates the potential application of the developed corrosion models as a design tool, by applying optimization techniques to determine coating configurations with maximized protective ability.
by Samuel R. Cross.
Ph. D.
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Jadhav, Niteen. "Novel Conducting Polymer Containing Composite Coatings for the Corrosion Protection of Metal Alloys." Diss., North Dakota State University, 2013. https://hdl.handle.net/10365/27037.
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Corrosion is a persistent problem faced by manmade structures made up of metal alloys. Aluminum 2024-T3 is high strength, light weight alloy used in aerospace applications. It suffers from the problem of corrosion due to its composition. Cold rolled steel is employed in structural applications but undergoes severe corrosion when exposed to corrosive conditions. Coatings are one of the best avenues to protect metal alloys from the corrosion. Traditional coating systems such as barrier type coatings, metal rich coatings, and inhibitor containing coatings have their own drawbacks. Conducting polymers (CPs), such as polypyrrole (PPy) can be used for the corrosion protection of the metals. Redox activity in conjunction with corrosion inhibiting ion release ability make CPs as a promising candidate for the replacement for hexavalent chromates. However CPs porous nature, inherent insolubility, stiff chains, and poor mechanical properties pose significant hindrance towards their implementation in coatings. In order to overcome the problems associated with the CPs and to extract maximum functionality out of them, conducting polymer containing composites (CPCC) were developed. CPCC combines CPs with inorganic pigments in unique ways and pave for excellent properties. In this work, series of composites of PPy/Inorganic pigments (aluminum flakes, iron oxide, micaceous iron oxide, and titanium dioxide) were synthesized by ecofriendly, facile chemical oxidative polymerization. Core and shell morphologies of PPy with titanium dioxide and iron oxide were synthesized and employed for the corrosion protection of cold rolled steel substrate. Various dopants such as phosphate, nitrate, molybdate, vanadate, and tungstate were incorporated in the backbone of PPy. These composites were characterized for morphology, elemental composition, and conductivity by various techniques. Furthermore coatings based on these composite pigments were formulated on Aluminum 2024-T3 and cold rolled steel substrates. These coatings were exposed to salt spray and prohesion test conditions and electrochemically evaluated against corrosion by Electrochemical Impedance Spectroscopy (EIS), DC Polarization, galvanic coupling and Scanning Vibrating Electrode Technique (SVET). Effect of solvent in the composite synthesis and PPy morphology in the final composite on the protective properties of coating was investigated. Effect of corrosion inhibiting anions on the final performance properties was also evaluated.U.S. Army Research Laboratory (Grant No. W911NF-09-2-0014, W911NF-10-2-0082, and W911NF-11-2-0027)
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Wang, Di. "Sustainable corrosion protection for metallic materials by Mussel adhesive protein modified lignin film." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-275728.
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Lignin has the potential to be used as green material to inhibit the corrosion of metallic substrates. Mussel adhesive protein is used to modify lignin due to its great adhesive and film forming abilities. Electrochemical impedance spectroscopy (EIS) has been applied to in-situ measure the corrosion resistance of the formed surface composite films in the corrosive environment. The equivalent circuit is used to fit the EIS data to obtain the quantitative results of the surface films. The results show that MAP modified lignin composite film can provide enhanced corrosion protection to the carbon steel substrate and presents self-healing property.Lignin har potential att användas som grönt material för att hämma korrosion av metalliska underlag. Mussellhäftande protein används för att modifiera lignin på grund av dess stora lim- och filmbildningsförmåga. Elektrokemisk impedansspektroskopi (EIS) har applicerats för att mäta korrosionsbeständigheten hos de bildade ytkompositfilmerna i den korrosiva miljön. Ekvivalentkretsen används för att passa EIS-data för att erhålla kvantitativa resultat från ytfilmerna. Resultaten visar att MAP-modifierad ligninkompositfilm kan ge förbättrat korrosionsskydd för kolfastsubstratet och uppvisar självhelande egenskaper.
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Sadeghimeresht, Esmaeil. "Corrosion Behavior of HVAF-Sprayed Bi-Layer Coatings." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-9929.
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In a variety of engineering applications, components are subjected to corrosive environment. Protective coatings are essential to improve the functional performances and/or extend the lifetime of the components. Thermal sprayingas a cost-effective coating deposition technique offers high flexibility in coatings' chemistry/morphology/microstructure design. However, the inherent pores formed during spraying limit the use of coatings for corrosion protection. The recently developed supersonic spray method, High-Velocity-Air-Fuel (HVAF), brings significant advantages in terms of cost and coating properties. Although severely reduced, the pores are not completely eliminated even with the HVAF process. In view of the above gap to have a high quality coating, bi-layer coatings have been developed to improve the corrosion resistance of the coatings. In a bi-layer coating, an intermediate layer is deposited on the substrate before spraying the coating. The electrochemical behavior of each layer is important to ensure a good corrosion protection. The corrosion behavior of the layers strongly depends on coating composition and microstructure, which are affected by feedstock material and spraying process. Therefore, the objective of the researchis to explore the relationships between feedstock material, spraying process, microstructure and corrosion behavior of bi-layer coatings. A specific motivationis to understand the corrosion mechanisms of the intermediate layer which forms the basis for developing superior protective coatings. Cr3C2-NiCr top layer and intermediate layers (Fe-, Co- and Ni-based) were sprayed by different thermal spraying processes. Microstructure analysis, as well as various corrosion tests, e.g., electrochemical, salt spray and immersion tests were performed. The results showed a direct link between the corrosion potential (Ecorr) of the intermediate layer and the corrosion mechanisms. It was found that the higher corrosion resistance of Ni-based coatings than Fe- and Co-based coatings was due to higher Ecorr of the coating in the galvanic couple with top layers. Inter-lamellar boundaries and interconnected pores reduced the corrosion resistance of intermediate layers, however a sufficient reservoir of protective scale-forming elements (such as Cr or Al) improved the corrosion behavior.
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Feng, Zuwei. "Formation of sol-gel coatings on aluminium alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/formation-of-solgel-coatings-on-aluminium-alloys(7e6eed7e-959b-487d-bc3a-5950d584ca42).html.
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Organically modified sol-gel coatings have been investigated as potential replacements for chromate conversion coating of AA1050 and AA2024 aluminium alloys. The coatings were prepared by a combination of a completely hydrolysable precursor of tetra-n-propoxyzirconium (TPOZ), with a partially hydrolysable precursor of glycidoxypropyltrimethoxysilane (GPTMS). GPTMS contains organic functional groups, which are retained in the sol-gel coatings after the hydrolysis-condensation process. Different process parameters, e.g. GPTMS/TPOZ ratios, withdrawal speeds, solvent water concentrations, and curing temperatures were studied. Coatings produced using a low GPTMS/TPOZ ratio and a high withdrawal speed generated significant cracks due to the shrinkage of the coatings. It was found that increase of organic moieties reduced the shrinkage of the coatings and the tendency for crack formation. By controlling process parameters and ratios of organic and inorganic moieties, crack-free sol-gel coatings from 0.1 μm to 9 μm thick can be achieved. The sol-gel coatings formed are amorphous and contain organic epoxy-ether retained silicon oxide, silicon hydroxide, zirconium oxide, zirconium hydroxide, and zirconium acetate. The Si/Zr ratios of resultant sol-gel coatings are proportional to the initial GPTMS/TPOZ ratio. Cerium oxide nanoparticles were successfully incorporated into sol-gel coatings with a single layer and double layer sol-gel process. Through the dip coating process, crack-free sol-gel coatings, of varied thickness, were developed on different aluminium substrate, including electropolished superpure aluminium, magnetron sputtered aluminium with varied copper contents from 0 to 30 wt.%, and commercial AA1050 and 2024 aluminium alloys. Sol-gel coatings formed on commercial AA1050 and 2024 aluminium alloys revealed a significant passivation in 3.5 wt.% sodium chloride solution during anodic polarisation when the sol-gel coating is more than 1 µm thick and proper surface pretreatments of the alloys were used. Corrosion tests by immersion in 3.5 wt% sodium chloride solution and by salt spray in 5 wt.% sodium chloride solution revealed that sol-gel coatings successfully protected AA2024 aluminium alloy against the aggressive environment and have the potential to replace chromate containing coating systems.
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ASHIRGADE, AKSHAY A. "ENVIRONMENTALLY-COMPLIANT NOVOLAC SUPERPRIMERS FOR CORROSION PROTECTION OF ALUMINUM ALLOYS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1153245386.
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Persson, Björn, and johanna Svensk. "Corrosion protection of powder coatings : Testing the barrier properties and adhesion of powder coating on aluminum for predicting corrosion protection by Electrochemical Impedance Spectroscopy." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-36772.
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The choice of corrosion protection system depends on the environment and needed lifetime for the product. The right corrosion protection should be selected in a sustainable point of view, since a well-selected coating system can reduce the environmental and economical impact, by using less and better material. The systems used for classifying corrosion protection often give a passed/not passed result for the number of years it is expected to last in a specific corrosive environment. In the last decades, Electrochemical Impedance Spectroscopy (EIS) has become a popular method for evaluating corrosion protection for organic coatings. EIS can collect quantitative data by monitoring the coatings electrochemical behavior over time, which can be used for optimizing the coating system. The purpose of this thesis was to try to predict how different combinations of coating layers and substrates will perform as a corrosion protection, which could provide information that can optimize the coating process. In this thesis, EIS has been used as a test method to evaluate organic coating systems for corrosion protection, by looking at barrier properties and adhesion for powder coatings on aluminum substrates. The main part of the coatings were applied in the coating plant at Fagerhult AB, but an external supplier has been used as a reference. The powders used in the coating process were based on polyester resins and the substrates were different aluminum alloys. The EIS measurements were performed in the chemistry lab at the School of Engineering at Jönköping University and depending on the sample setup was each sample evaluated for two or four weeks of testing. Two groups of samples had intact coatings and a third group had samples with an applied defect in the coating. The analysis of sample setups with intact coatings showed that the topcoat absorbed water faster than the primer. The samples showed no significant degradation in corrosion protection for the evaluated period and could thereby not provide enough information to be able to conclude which setup give the best corrosion protection over time. The samples with a defect in the coating indicated that two of the substrates provided similar adhesion in the coating-substrate interface. The coating from the external supplier was also included in the test and it showed the best adhesion of the tested samples. The main conclusion is that the coating system used at Fagerhult AB provides a very good corrosion protection. Longer testing time with EIS measurements on intact coatings is needed to be able to rank the different sample setups by failure of corrosion protection.
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Weng, Duan. "Corrosion protection of metals by phosphate coatings and ecologically beneficial alternatives : properties and mechanisms /." [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11262.
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Waterman, Jay. "In Vitro Assessment of the Corrosion Protection of Biomimetic Calcium Phosphate Coatings on Magnesium." Thesis, University of Canterbury. Mechanical Engineering, 2012. http://hdl.handle.net/10092/7552.
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The use of magnesium for degradable implants can fill the need for temporary, load bearing, metallic orthopaedic implants without the risks and expense of further surgeries once the bone has healed. Mg is non toxic and biocompatible, but the corrosion rate in the body is too high. The rate will need to be moderated if these implants are to be made clinically useful.
A review of common orthopaedic coatings found that the biomimetic calcium phosphate coating process meets the criteria for a good coating. This process was designed for permanent implants, and its corrosion protection properties were unknown on Mg. The research presented here evaluates and optimizes aspects of the corrosion protection of biomimetic coatings in vitro.
To accurately identify the corrosion mechanisms of such coatings, the in vitro behaviour of several common simulated body fluids and buffer systems was evaluated.
The deposition of biomimetic coatings on Mg was compared to Ti. The effect of common surface treatments on the deposition, composition, and ultimate corrosion protection was identified in order to understand the corrosion properties of these coatings. Following the results, the biomimetic method was modified to optimize the protection by reducing the defects. The corrosion properties of these modified coatings were assessed in vitro.
The limitation of the biomimetic coatings was found to be in all cases sensitive to the defects present in the coating. While these could be minimized, they were not eliminated. This led to unfavourable corrosion properties. To solve this problem, a novel treatment was developed to give the biomimetic coatings self-healing properties. This treatment promoted local repair in the coating at the defects, greatly improving the corrosion properties.
The in vitro model was increased in complexity by adding first amino acids, then proteins. The corrosion behaviour of the coatings was compared in these solutions to understand the effects of these molecules. The data gathered will help to build a better model of in vivo corrosion, and allow better prediction of the performance of biomimetic coatings for corrosion resistance.
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Wang, Yingying. "Electrochemical behavior of cold sprayed coatings dedicated to corrosion protection applications : Role of microstructure." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0026.
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Le Cold spray est une technique de réalisation de dépôts épais par projection à haute vitesse de particules. Pour cette technologie, la température du gaz vecteur reste inférieure au point de fusion de poudres projetées. Dans ce cas, les mécanismes d’adhésion sont liés aux hautes déformations plastiques que subissent les particules lors de leur impact avec le substrat. Parmi la grande variété de poudres disponibles, trois compositions ont été retenues pour ce travail. Elles autorisent l’élaboration (i) d’alliage d’aluminium, (ii) d’acier inoxydable et (iii) de magnésium. L’ajout de particules de SiC (en fonction de leur quantité ou taille) aux poudres d’aluminium a également permis de modifier les propriétés mécaniques (telle que la dureté) des couches produites. En formant des couches denses et très peu poreuses, les revêtements cold spray présentent tous les atouts des revêtements anti-corrosion. Ce travail de thèse s’est attaché à comprendre les relations existantes entre les paramètres de projection de poudres (température et pression du gaz vecteur, concentration et tailles des particules de SiC) et la qualité du revêtement obtenu, de définir les interfaces substrat / revêtement en fonction de leur composition chimique et leurs influences sur les propriétés de protection vis-à-vis de la corrosion du substrat. D’un point de vu microstructural, les résultats obtenus montrent que l’augmentation de température du gaz améliore la densité des revêtements. En diminuant le nombre de défauts mais également en optimisant la qualité de l’interface substrat/revêtement, la résistance à la corrosion se trouve également améliorée. Sur la base des différences de potentiel entre le revêtement et le substrat, il est possible de classer la nature des couches selon (i) les revêtements sacrificiels et (ii) les revêtements cathodiques. Quel que soit leur nature, les revêtements obtenus par cold spray présentent tous de bonnes propriétés barrières. Toute fois le mode de dégradation des revêtements sacrificielles a pu être assimilé à de la corrosion intergranulaire en lien avec la morphologie du dépôt mais également la distribution et la taille de particule SiC (cas particulier du revêtement d’aluminium). Si les essais de corrosion longue durée ne permettent pas d’amorcer la corrosion du substrat après dissolution du revêtement (pour les couches sacrifielles), des essais de corrosion galvanique autorisent une discrimination rapide de l’efficacité de la couche barrière. Ces tests électrochimiques sont également l’occasion de discuter des effets de la rupture d’un revêtement sur les cinétiques de corrosion des matériaux qu’ils protègent. L’ensemble des caractérisations métallurgiques ainsi que les tests électrochimiques menés sur les différents assemblages substrat/revêtements indiquent que la technique de cold spray est une méthode de choix pour la protection des matériaux de structures vis-à-vis de la corrosionCold spray is a relatively new coating technology in which coatings are produced by powders projected at high velocity. A significant feature of cold spray is that bonding is generated through severe plastic deformation at temperatures well below melting point of feedstock powders. In the present study, kinds of metallic coatings were produced by cold spray, including aluminum alloy coating, pure magnesium coating, magnesium alloy coating, stainless steel coating and SiC reinforced composite coatings. According to the manner in which the coating protects its substrate against corrosion, these cold sprayed coatings can be divided into two types, i.e. sacrificial anodic coating and noble barrier coating. The objective of this thesis is to verify the feasibility of producing both sacrificial anodic coating and noble barrier coating with high corrosion performance by cold spray, and meanwhile demonstrate the usefulness of electrochemical measurements for the characterization of corrosion protection properties of cold sprayed coatings. Besides material system, process parameters which influence corrosion performance of cold sprayed coatings were studied. Two factors, i.e. process gas temperature and process gas pressure were chosen. Results showed that higher process gas temperature leads to denser aluminum coating. Likely, higher process gas pressure improves denseness and corrosion resistance of stainless steel 316L coating. SiC reinforced aluminum based composite coatings were deposited on aluminum, stainless steel and magnesium substrate. Compared with aluminum coating, the addition of hard ceramic particle affects microstructure of coatings, and improves corrosion resistance by increasing denseness. Ceramic particle fraction and size affect coating microstructure in different ways and also influence corrosion behavior. In view of corrosion process, results indicate that corrosion protection of cold sprayed coating could be divided into two steps. In the first step, substrate is completely shielded by dense coating, no corrosion reaction occurs on substrate. In the second step, two types of coatings show totally different behavior. In the case of sacrificial anodic coating, substrate is under cathodic protection in galvanic couple; hence no corrosion (or weakened corrosion) happens on substrate. In contrast, when the coating is noble than substrate, the protection effect would be immediately interrupted once corrosive electrolyte penetrates through coating to interface. The overall results indicate that cold spray is a highly reliable alternative for production of coatings in anti-corrosion applications. Electrochemical measurements are useful tools for quality evaluation of corrosion behavior of cold sprayed coatings
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Carpenter, Phillip P. "Examination of the surface and interfacial properties of an epoxide-urethane resin for surface coatings." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/32637.
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Electrodepositable paints are used in the auto industry to provide the majority of the protection against corrosion to mild steel car body shells. They are generally epoxy/blocked isocyanate resins systems which are applied by action of an electropotential between the car and an anode. Upon heating to 175°C the blocked isocyanate deblocks, and crosslinking occurs predominantly via the formation of urethane and urea linkages. The aim of the project was to gain a better understanding of the factors which may affect the adhesion of the electrocoat resin polymer to a steel surface, to investigate possible replacements for the tin catalyst currently used, and to develop a quantitative mechanical test for paint adhesion. This was achieved by employing various analytical techniques including Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and mechanical testing.
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Reddy, Chandra M. "Improved corrosion protection of aluminum alloys by low temperature plasma interface engineering /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924918.
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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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Jamali, Seyed Sina. "Study on corrosion protection of organic coatings using electrochemical techniques : developing electrochemical noise method, effective of surface preparation and inhomogeneity of organic coatings." Thesis, University of Northampton, 2013. http://nectar.northampton.ac.uk/8862/.
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Abushwashi, Ibrahem. "Corrosion protection performance of cathodically protected oil and gas pipeline coatings around the transition temperature." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46840.
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Oil and gas pipelines are susceptible to corrosion by reacting with their environments. Water, oxidants, acids, and alkalis can act aggressively on the steel substrate. Over the years, corrosion has been the cause of many catastrophes. Thus, to prevent or slow down corrosion from taking place on steel substrate two techniques are primarily used. These techniques are coatings and cathodic protection. While the principles of cathodic protection is basically to reduce corrosion potential, coatings protect metals by breaking corrosion cells and provide shielding from corrosive agents. However, coatings should exhibit certain characteristics in order to be considered effective it terms of corrosion protection. Coatings have to withstand severe weather including temperature changes. Pipelines often operate at high temperatures due to the heat generated from crude frictions during transfer. With higher demands for crude oil and products, pipelines might be operated at flow rates more than normal and temperatures may exceed transition temperature (Tg) of the coatings.
All thermoplastic materials have an important material property resulting from the molecular movement of the side chains of the polymer, Tg. It affects many polymer properties. In literature, it is not quite clear whether Tg affects corrosion protection properties or not. In this work, behavior of two polymer coatings, namely SP8888 and SP2888 provided by Specialty Polymer Coatings Inc., have been studied at temperatures around their Tg using Electrochemical Impedance Microscopy (EIS) in combination with Electrochemical Noise (EN). From the experimental work results, it was found that coating capacitance (Cc) has slightly increased and coating resistance (Rc) has decreased as temperature was increased over the range of test. There was a slope change for both Rc and Cc around Tg. Charge transfer resistance (Rct) has shown an abrupt drop as the temperature approached Tg. Generally, the estimated Tg value from Z modulus was in good compatibility with the Tg measured with other DSC technique.