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Alhamalawi, Mazen. "Offshore Wind Power Foundations' Corrosion Protection Strategy : Anlysis remotely controlled corrosion protection system and comparison to traditional corrosion protection of offshore wind foundation." Thesis, Linnéuniversitetet, Sjöfartshögskolan (SJÖ), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-103460.
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När en metall är omgärdad av en elektrolyt, så som havsvatten, kommer det att byggas upp en naturlig potential. Det sker en elektronvandring mellan materialet och havsvattnet och ju större potentialskillnad desto större sannolikhet att metallen kommer korrodera. Korrosion är en stor och viktig fråga för offshorekonstruktioner och byggnader. För att uppnå en konstruktions designade livslängd kan åtgärder vidtas med hänsyn till kapitalkostnader och drift- och underhållskostnader. Denna studie syftar till att jämföra ekonomiska för- och nackdelar hos de två korrosionsskyddssystemen Galvanic Anode Corrosion Protection (GACP) och Impressed Current Cathodic Protection (ICCP) på havsbaserade vindkraftsfundament. Det förstnämnda systemet använder offeranoder och det sistnämnda är ett katodiskt korrosionsskydd med hjälp av påtryckt ström. Studien bestod av flera steg av litteraturstudier där teori om korrosion och korrosionssystem användes för att till slut kunna jämföra valda korrosionsskyddssystem. Resultatet visar att GACP har fler fördelar och färre nackdelar än ICCP och skulle därmed vara mer ekonomiskt fördelaktig i marina miljöer. GACP ger också önskad effekt direkt vid installation och behöver inte någon strömkälla, ICCP är mer komplicerat och är inte effektivt förrän hela systemet är monterat och i drift. Dessutom behöver ICCP extra strömkälla samt kablage.When a metal is surrounded by an electrolyte, such as seawater, a natural potential will be built up. An electron migration between the material and the seawater will happen and the greater the potential difference, the greater the probability that the metal will corrode. Corrosion is an important issue when it comes to offshore structures. In order to achieve a structure designed lifetime, measures can then be taken with regard to capital costs and operating and maintenance costs. This study aims to compare the economic advantages and disadvantages of the two, Galvanic Anode Corrosion Protection (GACP) and Impressed Current Cathodic Protection (ICCP), corrosion protection systems on offshore wind power foundations. The first mentioned system uses sacrificial anodes and the second is a cathodic corrosion protection by an applied current. The study consisted of several stages of literature studies where theory of corrosion and corrosion systems was used to finally be able to make a comparison between selected corrosion protection systems. The result shows that GACP has more advantages and fewer disadvantages than ICCP and would thus be more economical. GACP, for example, is efficient during installation and does not need an additional power source, but ICCP is more complicated and not efficient until complete assembly of the entire system and requires additional power source and cables. Right now, there is no design standard available with detailed requirements and advice has been given as for galvanic anodes systems.
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Sababi, Majid. "Nanocomposite films for corrosion protection." Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-132240.
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This thesis describes technical and scientific aspects of new types of composite films/coatings for corrosion protection of carbon steel, composite films with nanometer thickness consisting of mussel adhesive protein (Mefp‐1) and ceria nanoparticles, and polymeric composite coatings with micrometre thickness consisting of conducting polymer and ceria nanoparticles in a UV‐curing polyester acrylate (PEA) resin. The influence of microstructure on corrosion behaviour was studied for a Fe‐Cr‐V‐N alloy containing micro‐sized nitrides with different chemical composition spread in martensitic alloy matrix. The Volta potential mapping suggested higher relative nobility for the nitride particles than the alloy matrix, and the nitrides with higher amounts of nitrogen and vanadium exhibited higher nobility. Potentiodynamic polarization measurements in a 0.1 M NaCl solution at neutral pH and ambient temperature showed passivity breakdown with initiation of localized corrosion which started in the boundary region surrounding the nitride particles, especially the ones enriched in Cr and Mo. Mefp‐1/ceria nanocomposite films were formed on silica and metal substrates by layer‐by‐layer immersion deposition. The film formation process was studied in situ using a Quartz Crystal Microbalance with Dissipation (QCM‐D). The film grows linearly with increasing number of immersions. Increasing Mefp‐1 concentration or using Mefp‐1 with larger size leads to more Mefp‐1 being deposited. Peak Force Quantitative Nanomechanical Mapping (Peak Force QNM) of the composite films in air indicated that the elastic modulus of the film increased when the film deposited had a higher Mefp‐1 concentration. It was also noted that the nature of the outermost layer can affect bulk morphology and surface mechanical properties of the film. The QCM‐D study of Mefp‐1 on an iron substrate showed that Mefp‐1 adsorbs at a high rate and changes its conformation with increasing adsorption time. The QCM‐D and in situ Peak Force QNM measurements showed that the addition of Fe3+ ions causes a transition in the single Mefp‐1 layer from an extended and soft layer to a denser and stiffer layer. In situ ATR‐FTIR and Confocal Raman Microscopy (CRM) analyses revealed complex formation between Fe3+ and catechol groups in Mefp‐1. Moreover, optical microscopy, SEM and AFM characterization of the Mefp‐1/ceria composite film formed on carbon steel showed micron‐size aggregates rich in Mefp‐1 and ceria, and a nanostructure of well dispersed ceria particles in the film. The CRM analysis confirmed the presence of Mefp‐1/Fe complexes in the film. Electrochemical impedance microscopy and potentiodynamic polarization measurements showed that the Mefp‐1/ceria composite film can provide corrosion protection for carbon steel, and that the protection efficiency increases with exposure time. Composite coatings of 10 μm thickness composed of a UV‐curing PEA resin and a small amount of conductive polymer and ceria nanoparticles were coated on carbon steel. The conductive polymer (PAni) was synthesized with phosphoric acid (PA) as the dopant by chemical oxidative polymerization. The ATR‐FTIR and SEM analyses confirmed that the added particles were well dispersed in the coatings. Electrochemical measurements during long exposure in 0.1 M NaCl solution, including open circuit potential (OCP) and EIS, were performed to investigate the protective performance of the coatings. The results showed that adding ceria nanoparticles can improve the barrier properties of the coating, and adding PAni‐PA can lead to active protection of the coating. Adding PAni‐PA and ceria nanoparticles simultaneously in the coating can improve the protection and stability of the composite coating, providing excellent corrosion protection for carbon steel.QC 20131024
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Roberts, Erica W. "The corrosion protection of aluminium." Thesis, Bangor University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520064.
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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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Diaz, Tang Isabel. "Corrosion: inexorability versus durability." Revista de Química, 2016. http://repositorio.pucp.edu.pe/index/handle/123456789/100474.
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En general, un material tenderá a corroerse espontáneamente en un determinado medio si los productos de corrosión son más estables que el material de partida, o si bajo las condiciones de exposición la corrosión resulta favorecida. En la práctica, lo que se busca es extender la vida útil de estructuras, equipos o dispositivos, es decir, mejorar su durabilidad.In general, a material will tend to corrode in a specific environment when the corrosion products are more stable than the starting material or, when exposed to certain conditions, a corrosion process results favored. In general practice, the goal is to extend the service life of structures, equipment or devices, that is, to improve their durability.
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Verdier, Stéphane. "Corrosion et protection anti-corrosion de l'alliage de magnésium AM60." Grenoble INPG, 2003. http://www.theses.fr/2003INPG0030.
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Nous avons étudié la corrosion de l'alliage de magnésium AM60 d'un point de vue microstructural et à l'aide de méthodes électrochimiques, dans une solution saturée de magnésie, et en milieu chlorure de sodium. Pour limiter la corrosion de l'alliage AM60 ou pour améliorer l'adhérence des revêtements rganiques, nous avons étudié deux traitements de surface. Le premier, à base de fluorure de irconium ou de titane entraîne la formation d'un film par réaction acide-base à l'interface métal-électrolyte. La structure et la composition du film obtenu ont été analysées par Microscopie Electronique à Balayage (MEB) ainsi que par Spectroscopie de Photo-électrons X (XPS). Ce traitement de surface ne protège pas l'alliage AM60 de la corrosion. Un second traitement de surface par anodisation plasma a été développé. Nous avons étudié a formation du film ainsi que sa structure et sa composition (MEB, Diffraction des rayons X). La résistance à la corrosion est faiblement améliorée par ce traitement.
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Keddie, Alastair John. "Computational modelling of corrosion protection systems." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439541.
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Bi, Huichao. "Corrosion protection by paint : cathodic disbonding." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:b92b86b0-abb0-4945-8f07-f394b9e9eb5b.
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This work investigated cathodic disbonding of an unpigmented phenalkamine-cured epoxy coating on mild steel, EC, exposed to 3.5 wt.% NaCl solution. Scanning Acoustic Microscopy (SAM), Scanning Kelvin Probe (SKP), Electrochemical Impedance Spectroscopy (EIS) and optical microscopy have been combined to conduct this study. Several factors affecting the cathodic disbonding process: Film thickness, Cation mobility, Electrolyte concentration, Temperature, Paint composition, Polarisation and Open circuit potential, have been investigated. SAM results show that the disbonding of EC with a linear scribe spreads outwards from the defect with blisters forming at the anodes (as shown in SKP potential maps) within the disbond. The disbonded region does not correspond to complete adhesion loss as verified by peel-testing. Semi-immersion tests show that disbonding under full- and semi-immersion conditions have similar behaviours and both follow parabolic kinetics indicating the disbonding is likely to be controlled by a transport process along the coating/metal interface. An intact epoxy coated mild steel panel coupled with bare mild steel shows that the cathodic reaction beneath the coating obeys Tafel law. A mathematical model simulating cathodic disbonding which produces realistic potential files and shows the oxygen reduction is mostly located near the disbond mouth has been developed.
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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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Bouzidi, Djamel. "Corrosion et protection cathodique des conduites souterraines." Mémoire, École de technologie supérieure, 2011. http://espace.etsmtl.ca/877/1/BOUZIDI_Djamel.pdf.
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De nos jours, la détérioration des conduites souterraines par le phénomène de corrosion est
devenue une préoccupation croissante des secteurs industriels et environnementaux dans les
pays développés. En effet, la croissance annuelle du nombre de bris surgissant dans les
réseaux d’aqueduc et les budgets énormes de réhabilitation qui en résultent sont à l’origine de
la recherche de techniques innovatrices en termes d’évaluation et de prévention contre
l’avarie de la corrosion.
Les conduites utilisées dans le système de distribution d'eau sont principalement fabriquées
en fonte. La dégradation par corrosion de ce type de conduites métalliques a reçu une grande
attention de la part des ingénieurs des municipalités, des compagnies de distribution d’eau et
aussi des producteurs de ces matériaux. Dans ce contexte, on révèle que l’absence d’une
opinion cohérente sur la performance en service de ces réseaux ne cesse de remettre en
question les causes plausibles de rupture, la résistance à la corrosion et les méthodes fiables
de prévention contre la corrosion. De ce fait, on s’est proposé cette thématique de recherche
dont l’objet principal est d’établir un modèle de diagnostic basé sur l’évaluation des
paramètres du sol entourant la conduite, l’analyse chronologique des séries de bris et
l’évaluation du système de protection cathodique lorsque appliqué. Les corrélations établies
entre les paramètres composant ce modèle ont permis de réaliser une inspection directe sur
les conduites aux sites jugés à risque afin d’évaluer l’activité de la corrosion développée sur
les surfaces externes des conduites d’aqueduc. En outre, l’ensemble des données recueillies
permettent de calculer la vitesse de corrosion et de la relier aux paramètres pertinents tels que
la corrosivité du sol, le pH et la teneur en ions chlorure.
Les résultats obtenus par cette étude confirment que la résistivité du sol est le paramètre le
plus pertinent ayant un effet important sur la vitesse de corrosion externe. Ce paramètre de
rupture a été à son tour relié à un ensemble de facteurs dont la concentration en ions chlorure
et le pH. Le modèle du diagnostic permet ainsi de classifier la corrosivité du sol entourant la
conduite selon la valeur des différentes variables indépendantes retenues. D’autre part, il a
été trouvé que pour le même sol, le premier critère explicatif du bris des conduites d’aqueduc
est l’année de pose de celles-ci. Cependant, les inspections réalisées ont démontré que dans
un sol de très faible résistivité, la corrosivité du sol semble avoir un impact crucial sur la
corrosion de la conduite, et ce indépendamment de l’année de son installation. Concernant
les systèmes de protection cathodique installés, il a été retenu que ces derniers sont
majoritairement fonctionnels mais avec des degrés de performance variables. Néanmoins,
une protection cathodique installée adéquatement demeure une solution efficace pour la
réduction des bris.
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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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Allison, Crispin. "Flexible liners for corrosion protection of pipelines." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7388.
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Flexible plastic liners are sometimes installed into new and existing oil and gas pipelines to prevent corrosion of the pipe wall. A practical difficulty of this method is that the plastic liners are permeable to gases, which can collect and form an annular space between the liner and the pipe. If the operating pressure in the pipe decreases then the collected gas can cause the liner to collapse and block the pipe. One method for overcoming this problem is to insert vents at intervals along the liner to allow the gas to escape into the pipe during depressurisation. However, there is concern that this arrangement might lead to excessive corrosion beneath the vent where the pipe wall is exposed. The rate of corrosion is expected to be controlled by the vent size but this principle needs to be confirmed by experiment. The work described in this thesis is aimed at investigating this corrosion by experiment for a range of conditions typical of oil and gas production. A novel crevice corrosion cell was designed, consisting of an X100 carbon steel plate and a sheet of transparent Perspex, separated by a thin gasket. A small hole in the Perspex simulated a liner vent and allowed carbon dioxide to reach the steel surface. Tests were carried out in 3.5% NaCl solutions saturated with carbon dioxide at 1 bar partial pressure. Corrosion rates along the length of the annular space were measured using the Linear Polarisation Resistance (LPR) technique on pairs of insulated X100 electrodes set into the plate. The corrosion rates within the annular space have been shown to be small compared to those in the bulk solution and to diminish rapidly with distance from the vent. Mathematical modelling, based on the transport of carbon dioxide, is described to explain these findings and support the experimental work. The effectiveness of the LinerVentTM, installed over the vent, in a turbulence pipeline was demonstrated. The benefit of applying cathodic protection within the annular space was also demonstrated. The results are discussed in terms of the fundamental corrosion principles and their practical implications
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Donatus, Uyime. "Corrosion protection and microstructure of dissimilar materials." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/corrosion-protection-and-microstructure-of-dissimilar-materials(b419af19-3459-4218-9aff-b1b857a36cb4).html.
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Corrosion Protection and Microstructure of Dissimilar Materials. A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy by Uyime, Donatus on the 30th of July, 2015.Investigations on the micro- and macro-galvanic corrosion mechanisms in un-coupled AA2024-T3 alloys, AA2024-T3 coupled with mild steel (with and without the influence of cadmium and under varying solution temperatures), dissimilar friction stir welds of AA5083-O and AA6082-T6 alloys and a friction stir welded AA7018 alloy have been carried out. Selected methods of preventing and / or minimising the investigated corrosion phenomena were also investigated. The investigation of the corrosion behaviour of the uncoupled AA2024-T3 alloy revealed that there are two distinct stages of polarization during the galvanostatic polarization of AA2024T3 alloy in de-aerated 3.5% NaCl solution. From the first stage, the relationships between the pitting incubation time, pitting potential and applied current density for AA2024T3 alloy in the de-aerated condition were established. Whilst studying the in situ corrosion phenomena on the uncoupled AA2024-T3 alloy using the scanning vibrating electrode technique (SVET),three distinct stages in the variation of the recorded current density values with time were revealed. Attempts were made to correlate these stages with the corrosion behaviour of the alloy. The study of the galvanic interactions between AA2024-T3 and mild steel revealed that AA2024-T3 is anodic to mild steel at room temperature, but polarity reversal of the couple starts (from a temperature as low as 35 oC upwards) when the couple is introduced into the solution above ambient temperature. Importantly, AA2024-T3 is clearly cathodic to mild steel at 60 oC, although with very low measured galvanic current values. Cadmium coating (at ambient temperature) on the mild steel reduced the galvanic corrosion of the couple by as much as 20 µA/cm2 because of the formation of a CdO/Cd(OH)2 layer on mild steel. In the study of the dissimilar friction stir welds of AA5083-O and AA6082-T6 alloys, it was observed that material flows (pushes but does not mix) more from the advancing side into the retreating side and that the mixture of materials is far from complete. Two welding speeds were compared; the welding speeds have no clear influence on the microhardness, but affected the mixing proportions in the flow arm and in the nugget stem. The faster welding speed resulted in increased susceptibility to corrosion because of the reduced tool rotation per weld length for heat generation and the mixing of materials. The heat affected zones of both alloys and the transition regions between the AA5083-O alloy and the AA6082-T6 alloy rich zones have been identified to be the regions that are most susceptible to corrosion. Anodizing the weld in order to minimise corrosion showed that the AA5083-O alloy rich zones materials, in the weld, oxidizes more during anodizing compared with the AA6082-T6 alloy rich zones. Sputtering deposition prior to anodizing, promotes the formation of a uniform oxide film across the entire weld zones and prevents the boundary dissolution that occurs when the dissimilar weld of AA5083-O and AA6082-T6 alloys is anodized in 4 M H2SO4 solution at 15 V at ambient temperature. The investigation of the corrosion susceptible regions in friction stir welded AA7018 alloy, which was based on the use of ISO 11846 immersion test and the potentiodynamic polarization technique in naturally aerated 3.5 % NaCl solution, revealed intergranular, crystallographic and second phase particle influenced mode of attack. The heat affected zone was found to be the most susceptible to corrosion.
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James, Liam A. "Graphene layers for corrosion protection of steel." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/235169/1/Liam_James_Thesis.pdf.
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Graphene coatings have previously been used on various metals to prevent corrosion. The corrosion of steels in modern environments is a costly and ongoing issue that may be aided by graphene coatings. This project focused on forming graphene coatings formed on steel samples in a quartz-tube furnace. The coatings were analysed for their quality, and corrosion testing was performed on the coated steel. The graphene coatings were found to have superior corrosion resistance compared to uncoated samples.
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AL-Shareefi, Hussein. "Neutral network corrosion control by impressed cathodic protection." Thesis, Högskolan Dalarna, Maskinteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:du-4258.
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Alamdari, Mikayil. "Corrosion protection and monitoring of off-shore structures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Oil and gas platforms are confronting a problem of ageing as there are many platforms that were constructed over 40 years ago. Every year, the offshore sector incurs considerable losses due to corrosion. On average, oil and gas companies use 6% of their annual income to fight against corrosion. This all in a short-term has a negative impact on the marine environment and in a long-term endeavour toward sustainable energy encountering difficulties. This thesis presents a novel corrosion inspection method by the implementation of the deep neural network and fuzzy logic models. Fuzzy logic is a suitable mathematical tool for the task since it is capable of handling imprecise information from the real world. The benefit of this approach lies in its ability to include personal experiences and acceptable deterministic models in the calculations. This approach can thus help to reduce the dependence upon the precise data, allow modelling even when a phenomenon is incompletely understood, and lessen the difficulties arising due to the complex computation required by more traditional methods. Moreover, image processing based on algorithms can do the automated inspection of external corrosion phenomena. A complete automated system for corrosion detection in pipelines comprises of a drone to flying over these pipelines and capturing photos and/or videos, and an image based on an algorithm to process these visual data and detect corrosion. The proposed deep learning approach effectively wards off the need for manual inspection and other non-vision based non-destructive evaluation techniques for pipeline corrosion which are cost-ineffective and interrupts the functioning of pipelines. Increased production frequently comes with an unknown cost of the increased rate of material degradation and threatening corrosion failures. Therefore, essential topics as corrosion data management and risk assessment are covered.
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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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Hosking, Niamh C. "Next generation corrosion protection for the automotive industry." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/14514/.
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Vehicle bodies are generally constructed from galvanized steel, which, together with phosphate and e-coat paint treatments, ensures corrosion resistance. The use of these materials alone cannot provide adequate corrosion protection to certain features that are inherent to vehicle body construction but are also vulnerable to corrosion, such as cut edges of panels and creviced joints. The use of further corrosion protection measures, (e.g. sealers, lacquers and waxes), is undesirable because they require additional manufacturing processes, increase weight and reduce recyclability of the vehicle. The potential benefits of using zinc-magnesium alloy coated steel (ZMG) as a substitute for conventional galvanized steel were investigated in this work. Cyclic corrosion testing in sodium chloride and acid rain-based environments was conducted on panels of ZMG and conventional galvanized steel and the resistance of each material to red rust initiation and propagation was assessed. ZMG offered approximately a 3-fold improvement in red rust resistance compared to galvanized steel in the sodium chloride test but ZMG's corrosion benefit was attenuated in the acid rain environment. Cyclic corrosion testing was also conducted on painted test panels incorporating geometric features; enhanced edge and crevice corrosion resistance was also observed for panels constructed from ZMG. Corrosion products formed in each environment were characterized using a suite of analysis techniques and mechanisms to explain the enhanced corrosion resistance of ZMG were proposed based on these products and on the literature. An inhibiting corrosion protection mechanism was suggested for ZMG whereby cathodic activity was retarded via the precipitation of insulating, sparingly soluble magnesium hydroxide. Further inhibition of cathodic activity has been attributed to the specific oxide layer (possibly magnesium oxyhydroxide doped with zinc) present at the ZMG surface. The observed efficacy of the corrosion protection mechanisms suggests that ZMG may allow improvement of the vehicle body corrosion protection system for vehicle weight and recyclability targets.
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Morshed, Ali. "Surface modification for corrosion protection of steel pipes." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271173.
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De, Rojas Ricardo R. (Ricardo Rafael De Rojas Pando) 1978. "New developments in steel reinforcement protection from corrosion." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8613.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (leaves 55-56).
Due to life-cycle costs considerations, the Federal Highway Administration has required that all their new bridge structures have a service life of more than 75 years. The practical use of adequate concrete cover, low water/cement ratio, and corrosion inhibitors and admixtures are not enough to satisfy this requirement. Corrosion still affects the reinforcing steel through the diffusion of chlorides. The steel reinforcement, the last line of defense, has to be addressed in order to protect reinforced concrete structures from corrosion and thus extend the service life. Today, new cost-effective technology has surfaced to address the problem. Nuovinox Stainless-steel clad reinforcing bars, fusion bonded epoxy (3M Skotchkot 426) and the recent Dual Phase Ferritic Martensitic bars (MMFXI/II steels) have emerged. This study describes each new reinforcement protection technology and compares them through cost, service life, availability and resistance considerations. The comparisons show that stainless-steel clad bars have the advantage over all other new reinforcement types. The fusion bonded epoxy closely followed while the MMFX steel, because of its lack of exposure, came in last. A prudent combination of the standard corrosion protection methods with these new technologies in steel reinforcement can potentially provide a cost-effective service of more than 75 years to a structure.
by Ricardo R. De Rojas.
M.Eng.
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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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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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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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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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Shi, Wei. "The effect of intermittent cathodic protection on corrosion protection in the intertidal zone." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-effect-of-intermittent-cathodic-protection-on-corrosion-protection-in-the-intertidal-zone(80f890c7-2498-4c7d-899e-76a80639ac1b).html.
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As an important technique for corrosion control in marine environment, Cathodic Protection (CP) should be applied with a full understanding of environmental conditions and a good consideration of current requirements. Early studies on different kinds of steel specimens in the intertidal zone show severe corrosion losses. Nevertheless, there is evidence that CP can work in these regions of a steel structure because electrolyte pathway can remain some time on thin wetted surfaces when tides recede. This research aims to study corrosion activities and their behaviour under the influence of CP in a thin layer of electrolyte as a simulation of the inter-tidal zone. By means of a mechanical vibrating probe, Scanning Vibrating Electrode Technique (SVET) may be used to study local activities at coating defects in a thin electrolyte layer. The effect of CP on the local currents at the defect site was confirmed by SVET and, significantly, the development of calcareous films under these conditions in seawater was also observed. Such films are found to be effective in the absence of cathodic polarisation and only failed after damage. In order to explore the performance of applying CP, a Finite Element (FE) model of electrically connected zinc and steel samples beneath a specific thickness of electrolyte has been created, with full polarisation curves implemented for each metal based on experimental results obtained. The influence of the electrolyte conductivity and the geometry of the electrodes has also been considered. A comparison can then be made between experimental investigation and computational modelling of this corrosion cell. Epoxy-coated and uncoated mild steel samples obtained in the simulated tidal facility were also investigated. The formation of calcareous films was confirmed. Calcareous films were protective under these intermittent wetting conditions. Techniques used to understand the performance include optical observation, Scanning Electron Microscopy (SEM) together with Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) analysis.
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Pacheco, Alexandre Rodrigues. "Evaluating the corrosion protection of post-tensioning grouts : standardization of an accelerated corrosion test." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2003. http://hdl.handle.net/10183/170210.
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Post-tensioning grouts, typically a mixture of cement and water (sand, mineral chemical admixtures can also be used), are not only designed to transfer stresses between cables and precast concrete, but also to protect prestressing strands against corrosive phenomena. A recent concern regarding post-tensioned structures is the possibility that corrosive agents may reach grouted steel tendons and start a sequence of events culminating in catastrophic collapse. This possible scenario motivated the creation of the Accelerated Corrosion Test (ACT) intended to measure the degree of corrosion protection for grouts used in post-tensioning applications. This test is currently recommended by the Post-Tensioning Institute (PTI). Although already in use, the ACT is not fully developed and researchers have been pointing out the need for further studies to evaluate the influence of the IR drop effect on ACTs (a loss in the applied potential due to the resistivity of corrosion cells) because this phenomenon is likely to skew results for grouts of significant different resistivity. Five different categories of grout (plain, prepackaged, with corrosion inhibitors, with silica fume, and with fly ash) were tested in an electrochemical setup capable of compensating for IR drop effects. Procedures are recommended for adoption in an improved version of the ACT standard.
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ZANOTTO, Federica. "CORROSION BEHAVIOUR OF THE AZ31 MAGNESIUM ALLOY AND SURFACE TREATMENTS FOR ITS CORROSION PROTECTION." Doctoral thesis, Università degli studi di Ferrara, 2010. http://hdl.handle.net/11392/2389286.
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Nowadays environmental conservation forces the transportation industry to manufacture lighter and low emissions transport vehicles. In this contest, magnesium alloys have found increasing attention by the automotive industry because of their low density associated with good mechanical properties. However the low corrosion resistance of magnesium alloys in wet environments is still a limiting factor against their widespread diffusion.
The aim of this research is both studying the correlation between microstructure and corrosion behaviour of a AZ31 magnesium alloy and developing eco-friendly protective technologies. In particular inhibitors and surface pretreatments with different organic compounds have been investigated.
The effect of microstructure on corrosion resistance of AZ31 alloy has been analyzed through a comparative study between the electrochemical behaviour of as-cast and hot rolled AZ31. Environmentally friendly sodium salts of mono-carboxylic acids have been studied as inhibitors of AZ31 alloy corrosion in a standard saline solution. Moreover, long chain sodium mono-carboxylates have been tested as promoters of conversion coatings for this alloy. Finally, significant improvements have been achieved by modifying the protective coatings obtained by 3-mercapto-propyl-trimethoxysilane through cerium nitrate or oxide nanoparticle additions.
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LE, GAL LA SALLE-MOLIN ANNIE. "Corrosion, passivation et protection du cuivre en solutions aqueuses." Paris 6, 1991. http://www.theses.fr/1991PA066198.
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La premiere partie de ce travail etudie les differents phenomenes accompagnant la corrosion du cuivre en solution aqueuse. Les principales conclusions des travaux precedemment publies dans ce domaine sont tout d'abord rassemblees et interpretees a la lumiere d'une etude thermodynamique des equilibres existant entre les differentes especes du cuivre. Les essais experimentaux effectues ensuite ont montre que la corrosion s'accompagnait de la formation d'une couche complexe dans laquelle coexistent oxides cuivreux et cuivriques, puis de sa desagregation partielle. Plusieurs methodes complementaires ont ete employees: methodes physiques d'analyse de surface, absorptiometrie et polarographie, ainsi que trace de courbes intensite potentiel et mesures d'impedance. Ces dernieres, et notamment l'etude des fonctions de transfert masse/potentiel et flux de matiere/potentiel (methode disque-anneau) nous ont egalement permis une premiere approche dans l'elaboration d'un mecanisme de corrosion du cuivre. La deuxieme partie de ce travail etudie differents moyens de lutte contre la corrosion du cuivre. L'utilisation d'un inhibiteur de corrosion, le benzotriazole, dont l'origine des proprietes inhibitrices a ete expliquee, s'avere possible. Enfin, la formation de revetements protecteurs prealablement a l'utilisation du metal au contact du milieu corrosif, a ete envisagee dans le cas ou l'emploi d'inhibiteurs n'est pas realisable. Nous avons ainsi mis au point la realisation de depots de benzotriazolate du cuivre ou de diphosphate de cuivre et teste les qualites protectrices de ceux-ci
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Biswas, Avidipto. "CORROSION PROTECTION OF COPPER IN OILY MEDIA: MICROSCOPIC MECHANISMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364487333.
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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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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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Sundaram, S. K. "Corrosion and electrochemical protection of molybdenum and molybdenum disilicide in molten silicate glass environments." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/18906.
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Riemer, Douglas P. "Modeling cathodic protection for pipeline networks." [Gainesville, Fla.] : University of Florida, 2000. http://etd.fcla.edu/etd/uf/2000/ane5967/Dissertation.pdf.
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Thesis (Ph. D.)--University of Florida, 2000.Title from first page of PDF file. Document formatted into pages; contains xxii, 263 p.; also contains graphics. Abbreviated abstract copied from student-submitted information. Vita. Includes bibliographical references (p. 252-262).
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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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Ajayi, Fredric. "Mitigating corrosion risks in oil and gas equipment by electrochemical protection : top of the line corrosion." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/mitigating-corrosion-risks-in-oil-and-gas-equipment-by-electrochemical-protection-top-of-the-line-corrosion(550870a4-9373-4872-a076-a52f48a5a4f2).html.
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This study investigated the corrosion processes at the top and bottom of carbon steel pipelines transporting wet gases, and studied possible chemical mitigation strategies. First, immersion tests were carried out using carbon steel to study the effects of de-aeration with high purity nitrogen gas on the corrosion rate. Secondly, the corrosion rate was assessed for varying chloride ion concentrations in an aerated environment. In general, increasing de-aeration time changes the corrosion mechanism from mass transfer oxygen reduction to water reduction reaction. However, oxygen solubility controlled the corrosion process in aerated solution containing different chloride ion concentrations. A special two-electrode cell was designed for the top of the line corrosion (TLC) electrochemical measurements but a conventional three electrode cell was used for the bottom of the line corrosion (BLC) measurements. The TLC rate increases with temperature, and X-Ray Diffraction (XRD) confirmed the presence of chukanovite {Fe2(CO3)(OH)2}and possibly ferrous carbonate corrosion products at 40oC and 60oC respectively. However, for the BLC, the cementite phase remained on the metal surface after preferential dissolution of the ferrite phase in the carbon steel. Addition of acetic acid (HAc) locally dissolved the initially FeCO3 film formed on the metal surface, causing local corrosion damage. Addition of methyl di ethanol amine (MDEA) as a pH stabiliser reduced TLC and BLC rates due to enhanced stability of FeCO3 at pH 5.7-6.3. When Zn2+ ions were added as ZnCl2, both Fe2O3 and ZnCO3 were formed at reduced corrosion rate. Whenever FeCO3 film was damaged/dissolved by HAc addition of neither pH stabiliser; MDEA nor hydrate preventer; mono ethylene glycol (MEG) could not re-establish a protective film on the metal surface. The following organic inhibitors were investigated as potential mitigators of TLC: 2-mercaptobenzimidazole (2MBI), 2-amino-5-ethyl-1,3,4-thiodiazole (AETDA), 2-phenyl-2-imidazoline (2PI), dicyclohexylamine (DHA), and a commercial inhibitor formulation (CI-A). The inhibition efficiency (IE%) was found to increase in the order CI-A > 2MBI > AETDA > DHA. Their efficiency increases (except DHA) with inhibitor concentrations both at top and bottom of the line. 2MBI and CI-A behaved as mixed inhibitors but AETDA behaved as cathodic inhibitor, all were best fitted to a simple Langmuir adsorption isotherm. However, IE% of DHA decreased at higher inhibitor concentrations. Surprisingly, 2PI inhibitor increased the corrosion rate, and the corrosion rate further increased with increase inhibitor concentrations. Weight loss measurements results of TLC are also presented which showed lower inhibition efficiency for all the inhibitors investigated compared with electrochemical measurements in similar environments. The free energy of adsorption (∆Goads values for 2MBI and AETDA are around -36kJ.mol-1 while for CI-A the value was -15kJ.mol-1 (-7kJ.mol-1 in the presence of HAc). This is evidence for adsorption of 2MBI and AETDA on the metal surface by chemisorption with CI-A by physisorption. XPS analysis confirmed the presence of FeCO3 and FeOOH as corrosion products in the brine solution in the absence and presence of HAc containing different corrosion inhibitors.
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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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Leleu, Samuel. "Vers une nouvelle méthode efficace et respectueuse de l'environnement pour la protection contre la corrosion des alliages de magnésium pour l'industrie aéronautique." Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/20134/1/Leleu_Samuel-20134.pdf.
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Les alliages de magnésium représentent une alternative à l’utilisation d’alliages d’aluminium ou de matériaux composites, en particulier dans le secteur aéronautique dans l’objectif de réduire la masse des structures. Ces travaux de thèse ont pour but de participer au développement de nouvelles méthodes de protection des alliages de magnésium, plus efficaces et respectueuses de l’environnement. Pour mener à bien ces travaux, des techniques électrochimiques, en particulier la spectroscopie d’impédance électrochimique, ont été couplées à des mesures par microscopie à force atomique (AFM), à des analyses par spectroscopie d’émission atomique à plasma induit (ICP-AES) et par spectroscopie de masse d’ions secondaires à temps de vol (Tof-SIMS) ainsi que des essais normalisés industriels. Tout d’abord, la résistance à la corrosion en milieu Na2SO4 de trois alliages de magnésium contenant des terres rares (WE43, EV31 et ZE41) a été étudiée et comparée à celle de deux alliages riches en aluminium (AZ31 et AZ91) et à celle du magnésium pur. Pour tous les alliages, il a été montré que les particules intermétalliques agissent comme des cathodes locales. Cet effet de couplage galvanique est plus marqué pour les particules riches en terres rares, en particulier dans le cas de l’alliage EV31. Conjointement, la corrosion est contrôlée par la dissolution de la matrice riche en magnésium et par le recouvrement progressif de la surface métallique par un film d’oxydes/hydroxydes. Ce film est plus protecteur pour les alliages que pour le magnésium pur mais cet effet bénéfique n’est toutefois pas suffisant pour compenser le rôle néfaste joué par les particules intermétalliques. Au final, l’ajout de terres rares augmente la vitesse de corrosion des alliages de magnésium en milieu Na2SO4 par rapport à celle des alliages AZ ou celle du magnésium pur. Dans le cas de l’alliage WE43, qui a été retenu pour la suite de l’étude, il a été montré que le film protecteur d’oxydes est plus mince et plus stable que celui formé sur le Mg pur, en particulier en présence d’ions chlorure. Ces résultats ont été expliqués par l’incorporation des éléments d’alliages, comme l’yttrium, qui serait responsable de la formation d’un film d’oxydes plus compact. Puis, plusieurs méthodes de protection ont été envisagées dans le but d’obtenir une résistance à la corrosion compatible avec les exigences de l’industrie aéronautique. Un traitement d’anodisation, développé par la société Prodem et appelé CEP, en combinaison avec plusieurs primaires de peinture sans chromate, proposés par la société Mapaéro (hydrodiluable ou haut-extrait sec) ont été évalués et comparés aux solutions de référence chromatées. Il a été montré que les traitements de conversion actuels, même en présence de primaire chromaté, ne permettent pas une protection efficace des alliages de magnésium. Le traitement CEP, de par sa structure poreuse, permet une bonne adhésion avec les primaires. Les meilleures performances ont été obtenues pour le traitement CEP revêtu par le primaire haut-extrait sec. Des analyses supplémentaires ont montré que l’ajout d’un vernis permettait d’obtenir un système de protection prometteur pour le remplacement des systèmes de référence sur la base des exigences clés aéronautiques.
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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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Doherty, Matthew James. "Corrosion protection of metal packaging containers : the role of lacquers." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409716.
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Chadwick, Rennie. "Performance of concrete repair materials as corrosion protection for reinforcement." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/757/.
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Padovani, Cristiano. "Corrosion protection of friction stir welds in aerospace aluminium alloys." Thesis, University of Birmingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446319.
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Oleiwi, H. M. "Using cathodic protection to control corrosion of reinforced concrete structures." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/47895/.
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Cathodic protection (CP) has been increasingly used on reinforced concrete structures to protect steel reinforcement from corrosion. However, due to the complexity of environmental conditions, the specifications in national and international standards are still open to discussion in engineering practices for their accurate suitability. To some extent, the design aspects are still based on practical experience. It implies a great deal of estimations and assumptions. The research conducted in the thesis aims to address some of these challenges. To obtain reliable experimental results, the present study at first investigated the influence of experimental methods on the measurement of concrete electrical resistivity. It studied the effect of alternative current (AC) frequency, electrode materials and electrode configuration. Based on the results, an optimised method was decided for all the series of the experimental tests in this study. The CP study consists of two major works. The first one was to investigate the chloride contaminated concrete exposed to atmospheric condition. Impressed constant current method was adopted for the operation of CP. A series of electrical and electrochemical measurements were conducted for concrete resistivity, corrosion potential, corrosion rate, degree of polarization, instant-off potential and four-hour potential decay. An evaluation on the current adopted criterion in standards has been carried out on the experimental results. The second work was to investigate the corrosion of rebar in concrete specimens submerged (fully and partially) in salty water. For such more corrosive environment, a comparison between the impressed CP operation using constant current and that using constant potential has been conducted. The experiments evaluated the effects of the two major environmental factors, i.e. water and chloride contents, on reinforced concrete durability. The work provided a deep understanding on the electrochemical behaviour of the reinforced concrete system and effectiveness of CP implementation under severe conditions. The research work has an important contribution to fundamental science of corrosion and reinforced concrete deterioration, and the technology and practical application of CP for reinforced concrete structures. The main results of this work indicate the important influence of the frequency and electrode configuration on the electrical resistance measurement. For the reliability of electrical resistivity measurement, a high frequency of 10,000 Hz and an internal carbon fibre electrode method are recommended. Regarding the CP for the chloride contaminated reinforced concrete exposed to the atmosphere, it is suggested that adopting an instant-off potential of -500 mV with respect to Ag/AgCl/0.5KCl reference electrode can provide sufficient protection for the reinforced concrete of up to 0.59 % total chloride by weight of concrete, or concrete resistivity is greater than 6.7 kΩ.cm. Furthermore, it was found that the 100 mV depolarization criterion for the evaluation of CP performance gives an overestimated protection. A depolarization of 50 mV is therefore proposed. In terms of the submerged specimens, the results showed that the water content and chloride content should be explicitly related to the corrosion state rather than through a single parameter of the concrete resistivity for the complicated situations because the water content will affect the oxygen transportation in concrete, and the oxygen availability at the rebar surface will play an important role in the corrosion process, and this is unassessable by concrete resistivity. Moreover, 4 or 24 hours for the 100 mV depolarisation criterion in standards is not applicable for CP assessment where concrete structures are fully submerged due to the low availability of oxygen. On the other hand, the depolarization criterion can be used if the specimens are partially submerged, but different parameters affect the depolarization value such as the magnitude of the applied protection current or potential, chloride concentration, oxygen availability and time of depolarization.
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Phadnis, Ameya. "Corrosion Protection of Low Carbon Steel By Cation Substituted Magnetite." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271878/.
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Surfaces of low carbon steel sheet were modified by exposure to highly caustic aqueous solutions containing either chromium or aluminum cations. Corrosion resistances of such surfaces were compared with that of steel surfaces exposed to plain caustic aqueous solution. In all cases a highly uniform, black coating having a spinel structure similar to magnetite (Fe3O4) was obtained. The coated steel surfaces were characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrophotometry (FTIR). Polarization resistances (Rp) of modified steel surfaces were measured and compared with that of bare steel surfaces. Results indicate that chromium (Fe2+ Fe3+x Cr3+1-x) or aluminum (Fe2+ Fe3+x Al3+1-x) substituted spinel phases formed on steel surfaces showed higher Rp values compared to only magnetite (Fe2+ 2Fe3+O4) phase formed in the absence of either chromium or aluminum cations. Average Rp values for steel surfaces with chromium containing spinel phase were much higher (21.8 k?) as compared to 1.7 k? for bare steel surfaces. Steel surfaces with aluminum containing spinel phase and steels with plain magnetite coated samples showed average Rp values of 3.3 k? and 2.5 k? respectively. XPS and EDS analysis confirmed presence of cations of chromium and aluminum in Fe3O4 in cation substituted samples. FTIR results showed all coating phases were of spinel form with major absorption bands centered at either 570 cm-1 or 600 cm-1 assigned to Fe3O4 and ?-Fe2O3 respectively.
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GANDHI, JASPREET SINGH. "ELECTRODEPOSITION OF ORGANOFUNCTIONAL SILANES FOR IMPROVED CORROSION PROTECTION OF METALS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1097867674.
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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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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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Ouellet, Steeven. "Corrosion et protection du nickel en milieux aqueux faiblement alcalins." Thesis, Université Laval, 2009. http://www.theses.ulaval.ca/2009/26051/26051.pdf.
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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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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.