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1
Tan, Swee Hain. "Organic corrosion inhibitors." Thesis, Tan, Swee Hain (1991) Organic corrosion inhibitors. PhD thesis, Murdoch University, 1991. https://researchrepository.murdoch.edu.au/id/eprint/333/.
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The overall aims of this thesis were to conduct a broad survey of possible organic corrosion inhibitors in near-neutral chloride solutions and to elucidate the mechanisms of such action.
Altogether, 130 organic compounds were studied as possible corrosion inhibitors for pure iron, mild steel, copper and aluminium in aerated near-neutral (pH = 8.4) solutions containing 500 ppm NaCl and 100 ppm NaHCO, conditions often encountered in water-based automotive engine coolants. Inhibitor behaviour was investigated using steady-state electrochemical techniques including polarisation curves, Stern-Geary and corrosion potential (Em,) measurements. The organic compounds examined were found to be highly specific in their inhibitive action toward the metals studied. Typical examples of highly effective corrosion inhibitors were: sebacate and octanoate for pure iron; oleate and sebacate for mild steel; benzotriazole and 2-mercaptobenzothiazole for copper; and laurate and oleate for aluminium. E, was found to provide a rapid and convenient screening test for evaluating the inhibitor performance of organic compounds toward pure iron, mild steel and aluminium but was less useful for copper.
Good organic inhibitors were found to act as anodic inhibitors toward pure iron and mild steel but as anodic or mixed-type inhibitors toward copper. For aluminium, the majority of the compounds studied were found to act as anodic inhibitors. However,However, it was also found that only pit initiation was inhibited, i.e. existing pits were not prevented from developing. Optical microscopy of pitted aluminium surfaces indicated their nature varied considerably with inhibition efficiency. The role of complex formation in organic corrosion inhibitors was found to vary with the metal. Complexation of either iron(I1) or iron(II1) ions was found to have an insignificant effect on mild steel. The corrosion rate of copper was found to increase with the copper(LI) complex stability, thus indicating complex formation to be the rate-determining step. For aluminium, the observed effects were found to depend on complex stability. For weak to moderate complexants, inhibitor efficiency (measured as E,,) increased with increasing complexation. However, very strong complexing agents were sufficiently stable to dissolve the aluminium oxide surface, leading to poor inhibition. Aluminium pit morphology was found, using scanning electron microscopy, to change from hemispherical in the uninhibited solution to irregular in the presence of complexing inhibitors. No simple relationships between inhibitor efficiency and molecular structure were found. However, carbon chain length, the nature of functional group(s) and their location in the molecule were found to be important but varied according to the metal.
The inhibiting ability of sebacate (a straight chain C, dicarboxylate) was found not to be compromised by water movement (stirring) or pre-existing corrosion product layers. Immersion tests showed that passive film formation on mild steel in sebacate solution involved two stages and was complete only after -100 h immersion.
The ion selective properties of several iron(II1) carboxylates and hydrated iron(II1) oxide films were studied by membrane potential measurements in neutral sodium chloride solutions. Some specimens were also studied by Mossbauer spectroscopy. These results show that dicarboxylates are good inhibitors toward mild steel because they form impermeable films. Poor inhibitor performance is associated with the anion selectivity of the film which in turn appears to be related to the film purity. A model is suggested for the inhibition mechanism of mild steel corrosion by dicarboxylates in aerated near-neutral chloride solutions.
2
Tan, Swee Hain. "Organic corrosion inhibitors." Murdoch University, 1991. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060818.150145.
Full textAbstract:
The overall aims of this thesis were to conduct a broad survey of possible organic
corrosion inhibitors in near-neutral chloride solutions and to elucidate the
mechanisms of such action.
Altogether, 130 organic compounds were studied as possible corrosion inhibitors for
pure iron, mild steel, copper and aluminium in aerated near-neutral (pH = 8.4)
solutions containing 500 ppm NaCl and 100 ppm NaHCO,, conditions often
encountered in water-based automotive engine coolants. Inhibitor behaviour was
investigated using steady-state electrochemical techniques including polarisation
curves, Stern-Geary and corrosion potential (Em,) measurements.
The organic compounds examined were found to be highly specific in their
inhibitive action toward the metals studied. Typical examples of highly effective
corrosion inhibitors were: sebacate and octanoate for pure iron; oleate and sebacate
for mild steel; benzotriazole and 2-mercaptobenzothiazole for copper; and laurate
and oleate for aluminium.
E, was found to provide a rapid and convenient screening test for evaluating the
inhibitor performance of organic compounds toward pure iron, mild steel and
aluminium but was less useful for copper.
Good organic inhibitors were found to act as anodic inhibitors toward pure iron and
mild steel but as anodic or mixed-type inhibitors toward copper. For aluminium,
the majority of the compounds studied were found to act as anodic inhibitors.
However,However, it was also found that only pit initiation was inhibited, i.e. existing pits
were not prevented from developing. Optical microscopy of pitted aluminium
surfaces indicated their nature varied considerably with inhibition efficiency.
The role of complex formation in organic corrosion inhibitors was found to vary
with the metal. Complexation of either iron(I1) or iron(II1) ions was found to have
an insignificant effect on mild steel. The corrosion rate of copper was found to
increase with the copper(LI) complex stability, thus indicating complex formation to
be the rate-determining step. For aluminium, the observed effects were found to
depend on complex stability. For weak to moderate complexants, inhibitor
efficiency (measured as E,,) increased with increasing complexation. However, very
strong complexing agents were sufficiently stable to dissolve the aluminium oxide
surface, leading to poor inhibition. Aluminium pit morphology was found, using
scanning electron microscopy, to change from hemispherical in the uninhibited
solution to irregular in the presence of complexing inhibitors.
No simple relationships between inhibitor efficiency and molecular structure were
found. However, carbon chain length, the nature of functional group(s) and their
location in the molecule were found to be important but varied according to the
metal.
The inhibiting ability of sebacate (a straight chain C, dicarboxylate) was found not
to be compromised by water movement (stirring) or pre-existing corrosion product
layers. Immersion tests showed that passive film formation on mild steel in
sebacate solution involved two stages and was complete only after -100 h
immersion.
The ion selective properties of several iron(II1) carboxylates and hydrated iron(II1)
oxide films were studied by membrane potential measurements in neutral sodium
chloride solutions. Some specimens were also studied by Mossbauer spectroscopy.
These results show that dicarboxylates are good inhibitors toward mild steel because
they form impermeable films. Poor inhibitor performance is associated with the
anion selectivity of the film which in turn appears to be related to the film purity.
A model is suggested for the inhibition mechanism of mild steel corrosion by
dicarboxylates in aerated near-neutral chloride solutions.
3
El, Moaty Ibrahim S. "Surfactant properties of corrosion inhibitors." Thesis, University of Hull, 2011. http://hydra.hull.ac.uk/resources/hull:5807.
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Corrosion is one of the most common, costly and widespread industrial problems in the oil and gas production industry. Surfactant addition is one of many ways to inhibit the corrosion of metals, especially on hard-to-reach surfaces such as the inside of a pipe through which fluid is flowing. The application of small quantities of an inhibitor to production fluids is the most cost-effective method for imparting corrosion protection to a system. Despite the popularity of surfactants as corrosion inhibitors, their actual behaviour inside a pipeline is not well understood. The homologous alkylbenzyldimethylammonium chlorides CnBDMAC series is one of the most common corrosion inhibitors used in the oil industry. This thesis addresses some of the surfactant properties of these corrosion inhibitors which are not studied in detail (or often ignored) through electrochemical studies. Firstly, the adsorption behaviour of these corrosion inhibitors at the air-water interface was investigated as a function of the alkyl chain length, temperature and the concentration of the added electrolyte. The surfactant chain length and brine addition were found to have a great influence on the adsorption behaviour and hence on the critical micelle concentration (cmc). Secondly, the ability of CnBDMAC corrosion inhibitors to stabilize both oil-in-water and water-in-oil emulsions and the phase inversion of the emulsions as the inhibitor structure, temperature, electrolyte concentration and oil type change has been studied. The partitioning behaviour of C16BDMAC between an aqueous brine phase and an oil phase has been investigated as well as a function of electrolyte concentration. Studying the adsorption behaviour of surfactant corrosion inhibitors at solid-liquid interfaces provides important information about their action mechanism, which in turn helps in improving their efficiency. The adsorption behaviour of CnBDMAC molecules has been studied as a function of the surfactant chain length, temperature and electrolyte concentration using the Quartz Crystal Microbalance (QCM) technique. The QCM technique provides an effective, easy to setup and quick in-situ monitoring method for studying qualitatively the adsorption of surfactants at the solid-liquid interface. However, the determined adsorption isotherms were found to overestimate the amount of surfactant adsorbed. Therefore, the depletion method has been used to study the adsorption characteristics of CnBDMAC onto a stainless steel powder. Pipes used in oilfields for crude oil transportation are mainly made of mild steel. Accordingly, it is crucial to understand the adsorption behaviour of these corrosion inhibitors onto the mild steel surface. The effect of surfactant structure, temperature and electrolyte concentration on the adsorption behaviour of CnBDMAC onto mild steel particles using the depletion method has been investigated. In addition, the depletion method has been used to study the adsorption of CnBDMAC onto sand which is one of the main corrosion inhibitor consuming-solids encountered naturally in the oilfield. The adsorption studies performed revealed that these inhibitors have a strong affinity for sand particles, particularly at low temperatures and diluted inhibitor concentrations. Finally, the corrosion inhibition performance of hexadecylbenzyldimethylammonium chloride (C16BDMAC) corrosion inhibitor has been investigated through the linear polarisation resistance technique as a function of the added sand amount. A model has been proposed and applied successfully to determine the percentage decrease in the corrosion inhibition efficiency of C16BDMAC with changes in the amount of sand added.
4
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.
5
Elliott, David. "Corrosion inhibitors for load-bearing steels." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303645.
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6
Vuong, J. C. T. "Natural corrosion inhibitors for stainless steel." Thesis, University of Manchester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539460.
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7
Smith, G. A. W. "Design of environmentally-acceptable corrosion inhibitors." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593457.
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The first class of compounds investigated was the benzimidazoles. They are widely used in the pharmaceutical industry and have a low toxicity towards human and animal life, therefore, they are potentially suitable for use in a marine environment. These compounds have been reported to have some, although limited, use as corrosion inhibitors. With the aid of a molecular modelling package several benzimidazole molecules were functionalised to resemble the known inhibitor disodium sebacate. Satisfactory corrosion inhibiting properties were found for these compounds. The second compound to be investigated was Westvaco Diacid. It is a biodegradable, non-toxic, renewable natural resource, derived from the paper pulping process. It was found that by chemically altering its structure its corrosion inhibiting properties could be increased. The third source of potential corrosion inhibitor which was investigated was rapeseed oil. Again it is a non-toxic, renewable natural resource, consisting of the triglycerides of a mixture of fatty acids. Rapeseed oil was chemically modified, the products were not as potent corrosion inhibitors for mild steel as the previous classes of compound that were described. The corrosion inhibiting properties of the products which had been synthesised were tested by the weight loss method, on mild steel coupons, over a twenty day period, in distilled water and 10-3M potassium chloride solution. Examples of each class of compound showed no bactericidal activity when tested against sulphate reducing bacteria (SRB's). With the exception of the rapeseed oil derivative, all of the above compounds were tested for their corrosion inhibiting properties at high temperatures (80oC). Again the corrosion inhibiting properties were determined by the weight loss method, on mild steel coupons, in both distilled water and 10-3M potassium chloride solution.
8
Peggs, Lee James. "Electrochemical studies of iron corrosion inhibitors." Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285364.
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9
Rylands, Thaabit. "Corrosion of reinforcement in concrete : the effectiveness of organic corrosion inhibitors." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9946.
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Includes bibliographical references.Reinforcement corrosion in concrete has presented engineers with the challenge of finding ways of prolonging the service life of structures built in aggressive environments. One method of increasing the durability of concrete in aggressive environments is the use of corrosion inhibitors. In this work, two organic corrosion inhibitors were tested to observe their effectiveness in decreasing the rate of corrosion or delaying the onset of corrosion. One of the inhibitors was a migrating corrosion inhibitor while the other was an admixed inhibitor. The corrosion rate of reinforcement in concrete specimens used in this evaluation, was measured using the Linear Polarisation Resistance method. The performance of the admixed inhibitor was also measured in aqueous phase tests. Results of the tests conducted indicate that the admixed inhibitor does delay the onset of corrosion. The Mel caused short to medium term inhibition when the chloride concentration was less than 1.5%.
10
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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Yue, Jingyi. "Corrosion Behaviors of Coated Aluminum Alloys in Simulated Corrosive Environment." TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1485.
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This study investigated the corrosion of an aluminum alloy with and without coatings under simulated corrosive environments. Coatings were selected and applied from commercial materials and techniques, consisting of microceramic, epoxy primer, and topcoat. The experiments for coated specimens were carried out under various corrosive conditions, specifically, hydrodynamic flow, immersion in salt water and DI water, varying temperatures, and simulated sun light. The hydrodynamic conditions were simulated using a rotating cylinder electrode (RCE) with rotational speeds of 200, 400, 600, 800, and 1000 rpm. The immersion in saltwater and sunlight illumination tests were applied for 8 hours, and the simulated exterior temperature variation were cycled for 7 days. Polarization techniques were used to study the corrosion mechanism and calculate the corrosion rate of coated specimens under simulated salt water. Microstructure of coated specimens were identified by using atomic force microscopy (AFM) and optical microscope (OM) analysis. Results indicated that corrosions in the simulated salt water were generally more serious than those in the distilled water. This was especially true for bare aluminum alloys, that its corrosion rates in the salt water exhibited two orders of magnitude higher than those in the DI water. The combination of an environmentally friendly electrodeposited ceramic coating with a primer and topcoat, which results in a chromium-free coating, exhibited a higher polarization resistance and a lower corrosion rate than the traditional chromate conversion coating combination. In addition, for all coated Al alloys, the corrosion rate increased with increasing rotation speed. For immersion portion, immersion in salt water accelerated the pitting corrosion process and increased the corrosion rate of the aluminum alloy five times higher as compared to the samples without immersion. For the varying temperature portion, the rates of corrosion nearly doubled for bare and ceramic coated Al alloy, under varying temperature conditions for 7 days. Besides, addition of ionic liquid inhibitors, such as BMIMBR and BEIMCl, exhibited great improvement of corrosion resistances of aluminum alloy in the salt water. The corrosion rates of aluminum in the presence of inhibitors were almost one order of magnitude lower than that in the absence of inhibitors.
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Rocha, Alexandre Manuel Ferro. "Screening and development of corrosion inhibitors for al alloys." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13942.
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Mestrado em Engenharia de MateriaisThe goal of this work was to systematically seek and study the corrosion and corrosion protection of metallic materials and alloys. Aluminium alloys were the materials in scope due to their specific properties (low density and good mechanical properties) and practical applications, especially in aeronautical industries. The systematic screening and development of corrosion inhibition strategies for extensive localised corrosion conditions at selected Al alloy surfaces has been done. To study these concepts the combination of well-known integral techniques such as EIS with sophisticated localized scanning vibrating probe technique (SVET) was systematically applied. The advantages of combining different techniques and approaches are critically analysed and evaluated from the point of view of corrosion behaviour estimation on different aluminium alloy surfaces in chloride containing electrolytic environments.
O objectivo deste trabalho foi procurar/pesquisar de forma sistemática os efeitos da corrosão em estruturas metálicas e ligas, bem como a protecção das mesmas a este fenómeno. Devido às suas propriedades específicas (baixa densidade e boa resistência mecânica) e aplicações práticas em áreas como a aeronáutica, as ligas de alumínio foram os materiais estudados. Este estudo foi feito através do enquadramento e desenvolvimento de estratégias de inibição da corrosão, à superfície das ligas de alumínio seleccionadas, em condições de extensiva corrosão localizada. A combinação e sistemática aplicação de técnicas de análise electroquímica - desde técnicas bem conhecidas de análise integral (EIS) a técnicas sofisticadas para análise localizada (SVET) - foram as ferramentas usadas para levar a cabo este estudo. As vantagens desta abordagem e da combinação de diferentes técnicas serão criticamente analisadas e avaliadas do ponto de vista da estimativa do comportamento corrosivo nas superfícies das diferentes ligas de alumínio quando em contacto com ambientes electrolíticos que contêm iões cloreto.
13
Ghareba, Saad. "Inhibition of carbon steel corrosion by long alkyl-chain amino acid corrosion inhibitors." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104608.
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Carbon steel (CS) is the most commonly used material for equipment and pipes in the oil production processes. However, presence of water/salts and carbon dioxide, among other gases, in the oil is a serious problem due to increased corrosion rate of the material. The most common way of mitigating this problem is by using corrosion inhibitors. However, many common corrosion inhibitors that are in use today are health hazards. Therefore, there is a need to develop more environmentally compatible and biodegradable corrosion inhibitors. Bioorganic and naturally occurring molecules, such as amino acids, are the most obvious candidates. This work was aimed at studying the influence of some amino acids, 11-aminoundecanoic acid (11AA) and 12-aminododecanoic acid (12AA), as corrosion inhibitors for carbon steel (CS) in hydrochloric acid and some other electrolytes that might be used in certain industries.In this study the inhibiting effect of 12AA on corrosion of CS in CO2-free and CO2-saturated 0.5 HCl was investigated as a function of various parameters: inhibitor concentration, electrolyte pH, temperature, treatment time, CS surface roughness, electrolyte flow rate and pattern, effect of electrolyte type. In addition, the interaction of 11AA with the CS surface under selected experimental conditions was also investigated. It was found that 12AA inhibits both partial corrosion reactions, with a slightly stronger inhibition of the anodic corrosion reaction which indicated that 12AA acts as a mixed-type inhibitor. The corrosion protection mechanism is by formation of a surface-adsorbed 12AA monolayer that offers a hydrophobic barrier to transport of solvated corrosive ions to the surface yielding a maximum inhibition efficiency of ~98%. The adsorption of 12AA onto the CS surface was described by the Langmuir adsorption isotherm. The corresponding Gibbs energy of adsorption was calculated to be −26 and −28 kJ mol−1 in the CO2-free and CO2-saturated 0.5 M HCl, respectively. This indicated that the self assembled monolayers (SAM) formation process is spontaneous and reversible. PM-IRRAS measurements revealed that the SAM is amorphous, which could be attributed to the repulsion between the neighboring positively charged amine groups and also to a high heterogeneity of the CS surface. The study showed also that the 12AA can be used as an effective inhibitor of CS general corrosion in several other electrolytes including; acetic acid, perchloric acid and sodium chloride, but its application in nitric and sulfuric acid should be avoided. The corrosion inhibition of the CS surface by 12AA is also effective at higher pH values, although the corresponding corrosion inhibition efficiency decreased due to a decrease in 12AA solubility. 12AA was also confirmed to be an efficient corrosion inhibitor of a CS surface of different roughness.The effect of flow and flow pattern of CO2-saturated HCl on the corrosion inhibition of CS by 12AA was also investigated in a square duct, rotating disk electrode (RDE) and jet impingement cell configuration. 3 mM 12AA provided high corrosion inhibition efficiency in the square duct and RDE configuration. However, in 1 mM 12AA solution, the inhibition efficiency decreased with an increase in Reynolds number (Re), due to desorption of 12AA from the CS surface. 12AA was found to poorly protect CS in the impingement-jet configuration at low Re, while at high Re, acceleration of CS corrosion was recorded.Similar results were also obtained for inhibition of CS corrosion by 11AA. In fact, this molecule was found to better protect CS from corrosion than 12AA. This was attributed to the higher surface coverage of 11AA on the CS surface, i.e. the formation of a more compact 11AA monolayer.L'acier au carbone est le matériel le plus couramment utilisé pour les équipements et les pipelines reliés aux processus de production pétrolière. Toutefois, la présence de certains éléments comme l'eau, les sels and le dioxyde de carbone dans l'huile pose plusieurs problèmes reliés à l'augmentation du taux de corrosion du matériel. La façon la plus répandue d'éliminer ce problème est l'utilisation d'inhibiteurs de corrosion. Il est cependant important de mentionner que la majorité de ces inhibiteurs sont nocifs pour l'être humain. Il est donc nécessaire de développer des composés compatibles avec l'environnement et biodégradables et ceci peut être fait avec l'utilisation d'acides aminés.Ce projet a pour but d'étudier l'influence des acides aminés "11-aminoundecanoic acid" (11AA) et "12-aminododecanoic acid" (12AA) en tant que qu'inhibiteurs pour l'acier carbone dans l'acide chlorhydrique et plusieurs autres électrolytes utilisés dans certaines industries.Dans cette étude, l'effet inhibiteur du 12AA sur la corrosion de l'acier carbone dans une solution sans ou saturée en dioxyde de carbone et avec 0.5 M d'acide chlorhydrique a été étudié. Différents paramètres tels que la concentration des inhibiteurs, la concentration des électrolytes, le pH, la température, le temps de traitement, la rugosité de surface, le taux de flux et les différents types d'électrolytes furent analysés pour mieux comprendre le mécanisme de fonctionnement. De plus, l'interaction du 11AA avec la surface de l'acier à certaines conditions fut également prise en considération.Il fut démontré que le 12AA inhibait les corrosions partielles et démontrait une corrosion anodique légèrement plus inhibée. Ceci nous a donc indiqué que cet inhibiteur était de type mixte. Le mécanisme de protection de la corrosion se faisait par adsorption de l'inhibiteur 12AA et cela procurait une protection hydrophobique contre les ions corrosifs avec une efficacité de 98%. L'adsorption de 12AA à la surface de l'acier suit le modèle de l'isotherme de Langmuir. L'énergie de Gibbs correspondante de cette adsorption a été calculée comme étant environ −26 (sans CO2) et −28 kJ mol−1 (saturée en CO2 et 0.5 M HCl). Ceci a indiqué que la formation de la couche (composée d'une épaisseur) est amorphe et que cela est causé par la répulsion engendrée avec les groupes voisins de même charge positive et par le caractère très hétérogène de la surface. L'étude a aussi démontré que le 12AA peut être très efficace contre la corrosion de l'acier carbone et ce avec une grande variété d'électrolytes et d'acides. Il est important de mentionner que l'inhibiteur est inefficace contre l'acide nitrique et sulfurique. L'inhibiteur peut aussi réduire la corrosion lorsque le pH est élevé, mais voit son efficacité réduite dans ces conditions en raison de l'augmentation de sa solubilité. Finalement, le 12AA semble aussi performant avec toutes les rugosités. L'effet et le type de flux d'une solution de HCl saturée en dioxyde de carbone fut aussi étudié avec l'aide d'une électrode à disque rotatif. L'inhibiteur 12AA (3mM) se démontra très performant à contrer la corrosion dans un espace carré et avec un électrode à disque rotatif. Cependant, lorsque la concentration fut réduite à 1mM la performance de l'inhibiteur diminua et son nombre de Reynolds fut augmenté. Ceci fut causé par désorption de 12AA de la surface de l'acier. Cet inhibiteur ne fut donc pas efficace à protéger l'acier carbone dans ces conditions.L'étude de l'inhibiteur 11AA donna des résultats similaires. Cependant, la protection de l'acier carbone fut plus efficace qu'avec le 12AA à cause que le 11AA est capable de couvrir une surface plus importante tout en faisant une couche plus compacte.
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Dominguez, Olivo Juan M. "Electrochemical Model of Carbon Dioxide Corrosion in the Presence of Organic Corrosion Inhibitors." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1577092234789695.
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Wang, Hansheng. "Electrochemical investigation of "green" film-forming corrosion inhibitors :." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-40888.
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In this work, a comparative electrochemical study has been performed to evaluate corrosion inhibition property of several film-forming corrosion inhibitors provide by Akzo Nobel on carbon steel in a chloride solution. For carbon steel exposed to 1 M NaCl solution with and without added inhibitor, electrochemical measurements including electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) at different exposure time intervals, and potentiodynamic polarization at the termination of the exposure, have been performed to investigate the film forming process and to evaluate corrosion inhibition efficiency of the inhibitors, as well as its evolution with time. The corrosion resistance data obtained from the EIS and LPR measurements are in good agreement. The results indicate different inhibition properties of the inhibitors tested. The inhibition effect of SSF CI-1 is negligible in the first hour of exposure, but it increases steadily with time for 1 day, and then remains the same level during the exposure up to one week. SSF CI-2 exhibits a good inhibition effect in the first hour, but the effect decreases with time to a low level after 8 hours, and then increases again with prolonged exposure. SSF CI-4 shows a low inhibition effect during the first day, and then increases to a maximum level after three days’ exposure. For SSF CI-5 and SSF CI-6, the inhibition effect within 8 hours is relative low but higher than that of SSF CI-4, and the effect increases with time during prolonged exposure. The SSF CI-5 seems to be better than SSF CI-6 because of a more stable inhibition effect. The EIS results indicate that most of the inhibitors form a resistive surface film on carbon steel, which becomes more resistive and protective after several days’ of exposure. However, in the initial stage of exposure, the SSF CI-6 does not show an effect of formation of a resistive film on the surface. The potentiodynamic polarization measurements suggest that, SSF CI-1 and SSF CI-2 are anodic type inhibitor, SSF CI-4 is cathodic type inhibitor, and SSF CI-5 and SSF CI-6 are mix type inhibitor. Moreover, the inhibitors tested show a similar corrosion inhibition effect as mussel adhesive protein (MAP) at the low dosage level.
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Ciolkowski, Michal. "Mitigation of corrosion and scale by combined inhibitors." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/13633/.
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Corrosion and scale deposition on pipelines are two of the major flow assurance issues which have been recognized in the oilfield. Corrosion control of carbon steel pipelines requires understanding of the simultaneous occurrence of both processes. To date there have been few studies demonstrating the interactions between surface scale deposition and corrosion processes. Combined scale/corrosion inhibitors (mixture of scale and corrosion inhibitors) are gaining in popularity in the oil and gas industry as one of many methods to mitigate both those processes. A newly developed methodology of combined bulk jar scaling/bubble cell technique (corrosion) was used to assess the corrosion rate, CaCO3 deposition on the material surface and bulk precipitation in a CO2 environment. In this study the effects of single components of scale and corrosion inhibitors on the corrosion processes (general and localized corrosion) and scale deposition (bulk and surface deposition) have been investigated. Surface analysis techniques (SEM, EDX and Light Interferometry) and bulk analysis (Turbidity meter and ICP-MS) enable the corrosion/scale mechanisms to be studied in detail for X65 pipeline material. An experimental design method has been used to evaluate single and/or synergistic effect of single components of combined scale/corrosion inhibitor on the corrosion and scale processes. The methodology used in this study a newly-developed combined bulk jar scaling/bubble cell prove that is very effective tool in assessment of corrosion and scale interactions when they occurs simultaneously. Assessment of calcium carbonate precipitation on the sample showed that scale plays an important role of accelerating pitting corrosion by providing a suitable environment. XRD analysis showed that the calcium carbonate crystals which formed on the metal sample in the tests with 2-mercapthoethanol were calcite crystals only. The simple linear regression model was developed to predict corrosion and scale when these process occur simultaneously. The model also enables the interactions between the corrosion and scale inhibitor components to be quantified.
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Daviot, Jerome. "Organic inhibitors for metal corrosion in resist cleaners." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366779.
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Hansen, Joan Elizabeth. "A study of polymeric corrosion inhibitors for copper." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1057601491.
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Anstice, D. J. "Corrosion inhibitors for the rehabilitation of reinforced concrete." Thesis, Aston University, 2000. http://publications.aston.ac.uk/14159/.
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Four corrosion inhibitors namely sodium nitrite, sodium monofluorophosphate, ethanolamine and an alkanolamine-based mixture were studied by immersing mild steel bars for 42 days in model electrolytes of varied pH and chloride concentration which were intended to simulate the pore solution phase present within carbonated and/or chloride-contaminated concrete. Site trials were carried out on sodium monofluorophosphate and the alkanolamine-based inhibitor to study their depth of penetration into concrete. The influence of various carbonating atmospheres on the pore solution chemistry and microstructure of hydrated cement paste was investigated. Physical realkalisation of carbonated cement paste and a calcium nitrite-based corrosion rehabilitation system for chloride-contaminated cement paste were investigated by monitoring ionic transport within the pore solution phase of laboratory specimens. The main findings were as follows: 1,Sodium nitrite, sodium monofluorophosphate, ethanolamine and the alkanolamine-based mixture all behaved as passivating anodic inhibitors of steel corrosion in air-saturated aqueous solutions of varied pH and chloride concentration. 2,Sodium monofluorophosphate failed to penetrate significantly into partially carbonated site concrete when applied as recommended by the supplier. Phosphate and fluoride penetrated 5mm into partially carbonated site concrete treated with sodium monofluorophosphate. 3,The ethanolamine component of the alkanolamine-based inhibitor was found to have penetrated significant depths into partially carbonated site concrete. 4,Carbonating hydrated cement paste over saturated solutions of sodium nitrite resulted in significant concentrations of nitrite in the pore solution of the carbonated paste. Saturated solutions of sodium chloride, ammonium nitrate, magnesium nitrate and sodium dichromate were investigated and identified as alternatives for controlling the relative humidity of the carbonating environment. 5,Hardened carbonated cement paste can by physically realkalised to a limited extent due to the diffusion of hydroxyl ions under saturated conditions. A substantial proportion of the hydroxyl ions that diffused into the carbonated cement paste however, became bound into the cement matrix. Hydroxyl ion concentrations remained below 5mmol/l within the pore solution of the realkalised cement paste. 6, Nitrite ions penetrated significant distances by diffusion within the pore solution of saturated uncarbonated hydrated cement paste.
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Colares, Regilany Paulo. "Estudo da inibiÃÃo da corrosÃo do zinco por Ãons inorgÃnicos ecologicamente amigÃveis: molibdato, tungstato, silicato e fosfato." Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=5940.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoO cromato à amplamente utilizado como inibidor de corrosÃo. No entanto, à altamente tÃxico e carcinogÃnico, o que tem levado pesquisadores a buscarem alternativas ecologicamente amigÃveis a este inibidor. Dentre estes, molibdato, tungstato, silicato e fosfato surgem como potenciais candidatos por apresentarem propriedades inibidoras e serem atÃxicos. Assim, este trabalho tem por objetivo desenvolver um estudo sistemÃtico dos Ãons como inibidores da corrosÃo do Zn. Foram utilizadas soluÃÃes aquosas de NaCl 10-1 mol dm-3 com concentraÃÃes dos inibidores variando de 10-4 a 10-1 mol dm-3 . A eficiÃncia destes com relaÃÃo à corrosÃo do Zn foi avaliada empregando-se medidas do potencial a circuito aberto, curvas de polarizaÃÃo potenciodinÃmica e espectroscopia de impedÃncia eletroquÃmica. As tÃcnicas de Microscopia EletrÃnica de Varredura (MEV), Energia Dispersiva de Raios-X (EDX), DifraÃÃo de Raios-X (DRX) e Espectroscopia FotoeletrÃnica de Raios-X (XPS) foram usadas para caracterizar o Zn apÃs os ensaios de corrosÃo. Todos os Ãnions estudados inibiram a corrosÃo do Zn. Com as tÃcnicas de caracterizaÃÃo foi possÃvel identificar a presenÃa de filmes superficiais de silicato, tungstato, molibdato e fosfato na superfÃcie do Zn apÃs os ensaios de corrosÃo nas respectivas soluÃÃes contendo os inibidores
The chromate is widely used as a corrosion inhibitor. However, it is highly toxic and carcinogenic, which has done researchers to study environmentally friendly alternatives to this inhibitor. Among these, molybdate, tungstate, silicate and phosphate anions appear as potential candidates because they are non toxic. Thus, this work aims to develop a systematic study to investigate molybdate, tungstate, silicate and phosphate as corrosion inhibitors of zinc. Aqueous solutions of 10-1 mol dm-3 NaCl were used and the concentrations of the inhibitors ranging from 10-4 to 10-1 mol dm-3. The corrosion studies were carried out by open circuit potential measurements, potentiodynamic linear polarization and electrochemical impedance spectroscopy. The Scanning Electron Microscopy (SEM), X-Ray Dispersive Energy (XDE), X-Ray diffraction (XRD) and X-Ray Photoelectronic Spectroscopy (XPS) techniques were used to characterize the Zn after the corrosion tests. All the studied anions inhibited the zinc corrosion. The characterization techniques made possible to detect the presence of molybdate, silicate, tungstate and phosphate on the zn surface after the corrosion tests in the solution containing the corresponding inhibitors
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zhang, peilun. "Zn Corrosion in Alkaline Aqueous Electrolytes: Effect of Electrolyte Composition on Corrosion Rate and Inhibitors to Suppress Corrosion." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1618400150411797.
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Tan, Yong-jun. "Electrochemical studies on carbon dioxide corrosion and its inhibition." Thesis, Curtin University, 1996. http://hdl.handle.net/20.500.11937/359.
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This thesis mainly concerns the application of electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA) to the study of CO(subscript)2 corrosion of mild steel and its inhibition. The primary focus is on the use of EIS and ENA to monitor inhibitor film performance and to evaluate inhibitor film persistency.EIS was shown to be a suitable technique to study CO(subscript)2 corrosion product scale, and inhibitor films. The formation and deterioration of protective scales and inhibitor films is found to be accompanied by characteristic spectral changes and a rapid change in electrode impedance. EIS data were used to calculate corrosion related parameters such as the resistances and capacitances of inhibitor layers, and the charge transfer resistance and double layer capacitance. These parameters were used to analyse inhibitor mechanisms, determine corrosion rates and the persistence of inhibitor films.ENA is also a suitable technique to monitor the formation and deterioration of inhibitor films. It has the advantage of being able to monitor rapid processes which occur within one second. Several technical and theoretical developments were made in this thesis including the development of a new method of instantaneous corrosion rate measurement to study fast corrosion processes (the continuous noise resistance calculation method). Experimentally, the noise resistance was confirmed to be similar to linear polarisation resistance in the systems studies. The theoretical background and the advantages and disadvantages of the ENA technique are also discussed.Corrosion product scales formed under different conditions were investigated using EIS and surface analysis techniques. Temperature, pressure and exposure time were confirmed to be the important factors influencing the degree of protection given by the scale. The morphology of corrosion scales showed an obvious correlation to their protective ability. Electron microscopy revealed two types of crystal structures on corroded steel coupons. The smaller crystals associated with one of these structures was found to contribute most to corrosion protection.Several typical CO(subscript)2 corrosion inhibitors, including an imidazoline and a quaternised amine, were studied by EIS. A multi-layer model was employed to explain the EIS characteristics and self-repairing ability of imidazoline films. A quaternised amine film is most probably a physically or electrostatically adsorbed molecular layer which forms rapidly and desorbs easily.The deterioration of films, formed by commercial batch treatment inhibitors, was found to occur in three stages which were indicated or characterised by Bode phase-angle plots. A method to determine inhibitor film persistency was developed. This method is based on determining the three stages of inhibitor film deterioration, and the continuous measurement of corrosion rate, which is accessible at the second and third stages of film deterioration.
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Hristova, Roumiana. "Evaluation of corrosion inhibitors in chloride-contaminated reinforced concrete." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10389.
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The report describes research to determine the effectiveness of commercial corrosion-inhibiting admixtures on the corrosion of reinforcing steel in chloride contaminated concrete. Domestic and foreign publications were reviewed to locate performance data and current practices related to the use, testing and evaluation of corrosion inhibiting admixtures. The study consisted of identification and evaluation of the currently used corrosion-inhibiting admixtures in the United States and other countries. A list of available corrosion-inhibiting admixtures were appraised. Consideration was given to performance predictability, practicality, cost, and other pertinent factors. Five-year old "lollipop" concrete speciments containing sodium nitrite and dinitrobenzoic acid as corrosion inhibitors, and comparison with control specimens were studied using linear polarization and impedance spectroscopy. All mixes had different amounts of calcium chloride added. An equivalent circuit model considering the physical characteristics of the rebar/concrete interface was used to simulate the impedance spectra. The RC parameters obtained from the impedance simulation, including maximum phase angle shift, surface impedance and capacitive responses, were utilized to characterize the surface corrosion of embedded steel and to evaluate the effect of inhibitors with chloride content. The corrosion current densities determined by impedance measurement were compared with those determined using linear polarization and good agreement between the two methods was obtained.
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Airey, K. "An electrochemical and analytical study of iron corrosion inhibitors." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303326.
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Kelly, Brett. "Electrochemical Method for Characterization and Ranking of Corrosion Inhibitors." Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28657.
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One of the most cost-effective methods in mitigating corrosion effects is through the use of corrosion inhibitors. This work studied the performance of eight organic inhibitors on mild steel substrate through electrochemical characterization techniques, with the primary goal of incorporating a screening process to sift through the large selection of potential inhibitors without having to fully characterize them. The test methodology developed was successful at screening the potential corrosion inhibitors through linear polarization resistance (LPR) testing in NaCl electrolyte, narrowing the collection of inhibitors to the three most-promising chemicals, adrenalone, 3,4-dihydroxyphenylacetic acid and dopamine. The screened inhibitors proved effective in HCl electrolyte, reducing the corrosion rates of mild steel by over 85%. X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) testing were used to confirm surface adsorption of the molecules to the substrate, indicating the formation of a protective barrier film as the means of corrosion protection.
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Frey, Abigael. "A Mathematical Model of a Corrosion System Containing Inhibitors." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525449155620077.
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Jelena, Nakomčić. "Proučavanje korozije bakra u prisustvu odabranih derivata tiazola." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2016. https://www.cris.uns.ac.rs/record.jsf?recordId=101712&source=NDLTD&language=en.
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U ovom radu efikasnost odabranih derivata tiazola u inhibiciji korozije bakra u kiselojsulfatnoj sredini određena je u funkciji koncentracije inhibitora metodom merenjagubitka mase, elektrohemijskom impedansnom spektroskopijom i potenciostatskompolarizacijom. Polarizacionim merenjima takođe je određena zavisnost inhibitorskeefikasnosti od temperature i kinetički parametri procesa korozije bakra kao i modeladsorpcione izoterme prema kojem se odigrava proces adsorpcije inhibitora i odgovarajući termodinamički parametri. Merenjima kvarc kristalnom mikrovagom in situ je praćen proces elektrohemijskog rastvaranja bakra i adsorpcije ispitivanihinhibitora. SEM/EDX analizom proučavana je promena morfologije bakarne površineusled dejstva korozione sredine i rastvora inhibitora. Rezultati eksperimentalnihispitivanja korelirani su sa teorijskim proračunima na nivou teorije funkcionalagustine.In this work, the efficiency of selected thiazole derivatives in the inhibition of corrosion of copper in the acidic sulfate solution is determined in the function ofthe inhibitors concentration by weight loss method, electrochemical impedance spectroscopy and potentiostatic polarization. The dependence of the inhibition efficiency of temperature and kinetic parameters of the process of corrosion ofcopper as well as adsorption isotherm model according to which takes place the process of adsorption of inhibitors and the corresponding thermodynamic parameters were also determined by polarization measurements. A process of electrochemical copper dissolution and adsorption of tested inhibitors is followedin situ by quartz crystal microbalance measurements Changes in the morphology of the copper surface due to the effects of corrosive environment and the solutions of the inhibitors were studied by SEM/EDX analysis.The experimental results were correlated with theoretical calculations at the density functional theory level.
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Ahmed, Mohamed. "Inhibition of mild steel corrosion in cooling systems by low- and non-toxic corrosion inhibitors." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/inhibition-of-mild-steel-corrosion-in-cooling-systems-by-low-and-nontoxic-corrosion-inhibitors(7dc2367d-7352-4ab2-85b1-39b09d6487d8).html.
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The aim of the research in this thesis was to study how environmentally friendly corrosion inhibitors for cooling water systems might be developed and used. Firstly, reduced toxicity inorganic corrosion inhibitors (i.e. nitrite/molybdate) were considered. Secondly, non-toxic inhibitors based on mono and di-basic salts of carboxylic acids were studied systematically as a function of carbon chain length. For nitrite inhibitor alone, a concentration of 7 mM NaNO2 was effective to inhibit carbon steel in chloride media of 10 mM NaCl, while 10 mM nitrite was needed in sulphate media of 3.66 mM Na2SO4. However, it was found possible to significantly reduce the concentration of nitrite by adding molybdate in synergy. This was attributed to the nitrite passivation combined with ferrous molybdate salt film pore plugging thus promoting a continuous and protective film on the material within these media. Thus, in pH 6-10 an inhibition efficiency of 97% was recorded with a mixture of 3 mM nitrite/2 mM molybdate in both chloride and sulphate media and at 25°C and 60°C. However as the solution pH decreased below pH 4 the inhibition efficiency decreased to about 47%.In the second part of the study, the use of sodium salts of carboxylic acids with different chain lengths has been investigated. In this part a summary of the performances and limitations of both mono- and di-sodium carboxylate inhibitors are presented. For mono-carboxylates, the inhibition efficiency reached a maximum value of 95% in stagnant aerated solutions at a chain length of C=4 with a critical inhibition concentration of 6 mM in 10 mM NaCl solution. However the inhibition efficiency gradually decreased as the number of carbon atoms in the chain length increased to more than 8, or less than 4, and this was in agreement with surface hydrophobicity and contact angle results. For lower chain lengths, the carboxylate anion becomes more acidic and complexing of the metal ion while for longer chain lengths, the carboxylate anion becomes less soluble and tends to micellise wherby the active groups are no longer available for surface adsorption. For di-carboxylates the inhibition efficiency improved in 10 mM NaCl at a given chain length compared with mono-carboxylates, and continued to increase to C=8 (sebacate), which achieved excellent inhibition efficiency. However, sebacate is costly so a blend with ethyl hexanoate was found to be economically favoured.
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Chinthala, Sai Prasanna Prasanna. "Study of Corrosion Inhibitors for Reinforcement Corrosion of Low Carbon Steel in Simulated Pore Solution." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555601685519345.
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Stephens, Peter M. B. "Polynuclear transition metal complexes of tetraazamacroycles and their derivatives." Thesis, University of Kent, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385273.
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Sheng, Qi. "Designing Single Polymer Molecules as Gas Hydrate and Corrosion Inhibitors." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/70549.
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This study aims to develop next generation kinetic hydrate and corrosion inhibitors (KHCIs) for the oil and gas industry. Libraries of polymers with specific architectures were designed, synthesized and tested with both targets in mind. For this purpose, an innovative high-throughput hydrate screening method was developed and applied for the first screening tests. This study describes a systematic method for synthesizing and screening newly developed multifunctional inhibitors for both hydrate- and corrosion inhibition.
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McNeill, Laurie S. "Water Quality Factors Influencing Iron and Lead Corrosion in Drinking Water." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28242.
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Corrosion is one of the most complicated and costly problems facing drinking water utilities. Corrosion of iron pipes can lead to economic losses and customer complaints, while lead corrosion poses a serious health risk.
This work first synthesizes nearly 100 years of iron corrosion research to provide the water industry with an updated understanding of factors that influence iron pipe corrosion including water quality and composition, flow conditions, biological activity, and corrosion inhibitors. Potential impacts of upcoming regulations on iron corrosion are also considered. Next, a four-year study is presented that evaluated the effect of water quality and phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Surprisingly, many of the water quality parameters traditionally thought to influence iron corrosion were not controlling under these "worst case" stagnant conditions. Moreover, addition of phosphate inhibitors often had either no statistically significant effect or actually increased iron concentration, scale build-up and overall weight loss.
Temperature is often overlooked when corrosion of distribution systems pipes is considered. Temperature impacts many parameters that are critical to pipe corrosion including physical properties of the solution, thermodynamic and physical properties of corrosion scale, chemical rates, and biological activity. Moreover, variations in temperature and temperature gradients may give rise to new corrosion phenomena worthy of consideration by water treatment personnel. In laboratory experiments, cast iron samples at 5° C had 23% more weight loss, ten times higher iron release to water, and twice as much tuberculation compared to samples at 25°C.
For lead corrosion, hexametaphosphate inhibitors were proven to increase release of both particulate and soluble lead to drinking water by 200 - 3500% over a wide range of water qualities when compared to orthophosphate, effectively ending a long term debate as to their impacts. Utilities should consider these adverse effects whenever polyphosphate is used to prevent scaling or iron precipitation.Ph. D.
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Mennucci, Marina Martins. ""Influência de inibidores no comportamento de corrosão de aço CA-50 para armadura de estruturas de concreto"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-29052007-161636/.
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Neste trabalho, vários tipos de compostos foram testados com o objetivo de avaliar sua potencialidade para uso como inibidores de corrosão de armadura de aço carbono em concreto armado. Os aditivos testados foram benzoato de sódio, benzotriazol, carbonato de ítrio, polietilenoglicol, e hexametilenotetramina. Inicialmente foram realizados ensaios exploratórios para seleção dos candidatos potenciais entre os compostos testados com base na eficiência de inibição determinada por ensaios eletroquímicos, especificamente ensaios de polarização e espectroscopia de impedância eletroquímica. Os ensaios eletroquímicos foram realizados em uma solução sintética composta por 0,01N de hidróxido de sódio (NaOH) mais 0,05N de hidróxido de potássio (KOH), para simular a composição da solução dentro dos poros no concreto. O aditivo que apresentou melhor potencialidade para uso como inibidor de corrosão foi o benzotriazol (BTA). Após eliminação dos compostos que apresentaram potencial de plicação, e seleção do candidato com maior eficiência de inibição no meio de estudo, o efeito da sua concentração na resistência à corrosão foi avaliado. Soluções de nitrito de sódio foram também usadas nas mesmas oncentrações que as adotadas para as de BTA para efeito de comparação. O nitrito de sódio é um inibidor de corrosão já estabelecido para reforços de aço carbono em concreto, mas este tem sido associado com efeitos tóxicos. O benzotriazol (BTA) foi associado com eficiências de inibição sempre superiores às do nitrito de sódio nas mesmas concentrações. Um filme escuro e aderente foi formado na superfície do aço durante períodos longos de imersão no meio alcalino contendo BTA. Os resultados apontaram para o alto potencial de aplicação do BTA como aditivo inibidor da corrosão do aço em estruturas de concreto armado, podendo vir a substituir o nitrito nestas aplicações.In this work, various compounds were tested to evaluate their potential capability for their use as corrosion inhibitors of carbon steel reinforcement in concretes. The addit ives tested were sodium benzoate, polyethylene glycol, hexamethylenetetramine, benzot riazole and itrium carbonate. Initially, exploratory tests were carried out to select the ones to be used as corrosion inhibitors, based on the inhibit ion ef f iciency determined from elect rochemical tests, specifically polar ization tests and elect rochemical impedance spect roscopy. These tests were carried out in a solut ion composed of 0.01N sodium hydroxide (NaOH) and 0.05N potassium hydroxide (KOH) to simulate the composition of the solution inside the pores in concretes. The additive that presented the most promising potent ial to be used as cor rosion inhibitor was benzot r iazole (BTA). Af ter the elimination of some compounds and selection of the additive with higher corrosion inhibit ion efficiency in the test medium, the effect of its concent ration on the cor rosion inhibition efficiency was evaluated. Sodium nitrite solutions with the same concentrat ions as those solutions with BTA were tested for compar ison reasons. Sodium nitr ite is a well established corrosion inhibitor for carbon steel reinforcement in concretes but it has been related to toxic effects. The BTA was associated to higher corrosion inhibit ion efficiencies than that of sodium nitrite in similar concentrations. A blackish adherent film was formed on the steel surface exposed to BTA solut ions dur ing long periods of immersion in the alkaline medium. The results suggest that BTA is a potential candidate for subst itution of nit rites as corrosion inhibitor of reinforcements in concrete
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Tan, Yong-jun. "Electrochemical studies on carbon dioxide corrosion and its inhibition." Curtin University of Technology, School of Applied Chemistry, 1996. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=11433.
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This thesis mainly concerns the application of electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA) to the study of CO(subscript)2 corrosion of mild steel and its inhibition. The primary focus is on the use of EIS and ENA to monitor inhibitor film performance and to evaluate inhibitor film persistency.EIS was shown to be a suitable technique to study CO(subscript)2 corrosion product scale, and inhibitor films. The formation and deterioration of protective scales and inhibitor films is found to be accompanied by characteristic spectral changes and a rapid change in electrode impedance. EIS data were used to calculate corrosion related parameters such as the resistances and capacitances of inhibitor layers, and the charge transfer resistance and double layer capacitance. These parameters were used to analyse inhibitor mechanisms, determine corrosion rates and the persistence of inhibitor films.ENA is also a suitable technique to monitor the formation and deterioration of inhibitor films. It has the advantage of being able to monitor rapid processes which occur within one second. Several technical and theoretical developments were made in this thesis including the development of a new method of instantaneous corrosion rate measurement to study fast corrosion processes (the continuous noise resistance calculation method). Experimentally, the noise resistance was confirmed to be similar to linear polarisation resistance in the systems studies. The theoretical background and the advantages and disadvantages of the ENA technique are also discussed.Corrosion product scales formed under different conditions were investigated using EIS and surface analysis techniques. Temperature, pressure and exposure time were confirmed to be the important factors influencing the degree of protection given by the scale. The morphology of corrosion scales ++showed an obvious correlation to their protective ability. Electron microscopy revealed two types of crystal structures on corroded steel coupons. The smaller crystals associated with one of these structures was found to contribute most to corrosion protection.Several typical CO(subscript)2 corrosion inhibitors, including an imidazoline and a quaternised amine, were studied by EIS. A multi-layer model was employed to explain the EIS characteristics and self-repairing ability of imidazoline films. A quaternised amine film is most probably a physically or electrostatically adsorbed molecular layer which forms rapidly and desorbs easily.The deterioration of films, formed by commercial batch treatment inhibitors, was found to occur in three stages which were indicated or characterised by Bode phase-angle plots. A method to determine inhibitor film persistency was developed. This method is based on determining the three stages of inhibitor film deterioration, and the continuous measurement of corrosion rate, which is accessible at the second and third stages of film deterioration.
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Gemmill, R. J. "The passivation of aluminium in inhibited red fuming nitric acid." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376493.
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Phanasgaonkar, Alka 1956. "Diffusion and protection mechanisms of migratory corrosion inhibitors in reinforced concrete." Monash University, Dept. of Materials Engineering, 2000. http://arrow.monash.edu.au/hdl/1959.1/9200.
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Snowden, M. E. "Studies of corrosion inhibitors for the conservation of mild steel artefacts'." Thesis, University of Portsmouth, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247648.
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Garrett, Sharon Ann. "A study of inhibitors of the corrosion of aluminium-copper alloys." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295314.
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YANG, HAI. "PLASMA TREATMENT OF ORGANIC INHIBITORS FOR CORROSION PROTECTION OF AEROSPACE ALLOYS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1058383366.
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Elshami, Ahmed. "Efficiency of corrosion inhibitors used for concrete structures in aggressive environment." Nantes, 2012. http://www.theses.fr/2012NANT2035.
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La détérioration d'une structure en béton peut être dû à de nombreux processus, qui agissent individuellement ou en synergie. Quelques exemples de processus qui causent la détérioration des matériaux cimentaires comprennent des attaques sulfatique, des cycles gel-dégel, de la carbonation ou des attaques salins provoquant la corrosion des armatures dans le béton. La corrosion des armatures est l'un des phénomènes les plus importants qui réduit la durée de vie des ouvrages en béton, en impactant de façon importante le budget maintenance de la structure affectée. L’objectif de ce travail est d'étudier la durabilité à long terme de différents inhibiteurs de corrosion. D’une part, trois inhibiteurs de corrosion sont choisis comme représentatifs : le nitrite de calcium (CNI), l’éthanolamine (AMA) et le sodium monofluorophosphate (MFP). Ils sont incorporés dans trois bétons différents : le béton de ciment Portland (OPCC), le béton de ciment reconstitué avec 70% de ciment Portland et 30% de laitier (BCC) et le béton prêt à l’emploi (RMC). Afin d'étudier l'efficacité de ces trois inhibiteurs, quatre approches sont employées : une à l’échelle de la solution interstitielle de béton, une à l'échelle de la solution extraite de ciment, une à l'échelle du mortier et une à l'échelle du béton. L'étude est réalisée en employant des méthodes électrochimiques et analytiques afin de caractériser le mécanisme d'inhibition en présence d'ions chlore. D’autre part, l'objectif de cette étude est d'explorer l'efficacité d'un nouveau pigment inhibiteur de zinc-phosphate (ZP) obtenu par la conversion chimique et le traitement électrochimique cathodique. Cette étude est réalisée à l’échelle de la solution interstitielle de béton ainsi qu’à à l'échelle du mortierThe deterioration of a concrete structure may occur due to many processes, which act individually or synergistically. Some examples of processes that cause material deterioration include alkali aggregate reactivity, sulphate attacks, freezing, thawing, cycling, carbonation or salt attack inducing corrosion of concrete reinforcement. Corrosion of reinforcing rebars is one of the most important phenomenon’s that reduce the service life of a concrete structure, and causes a huge impact on the maintenance budget of affected structure. The objective of this research work is to study the long-term durability of different corrosion inhibitors. On the one hand, three additive corrosion inhibitors are selected as representatives : one is a calcium nitrite based corrosion inhibitor (CNI), the other corrosion inhibitors are ethanolamine (AMA) and sodium monoflurophosphate (MFP). They were admixed in water before casting of three different concretes (Ordinary Portland cement concrete (OPCC), blended cement concrete prepared with 30% slag in mass substitution of Portland cement (BCC) and ready-mix concrete (RMC)). In order to characterize the effectiveness of these inhibitors, four approaches are used: one at the level of pore concrete simulating solutions, one at the solution extract of cement level, one at the mortar level and one at the concrete level. The study was performed through the using electrochemical and analytical methods to discuss the inhibition mechanism in the presence of chloride ions. On the other hand, the objective of this study is to explore the efficiency of a new inhibitive pigment zinc-phosphate (ZP) used as coating for rebars and obtained by chemical conversion and cathodic electrochemical treatment, to protect carbon steel rebar against the corrosion by chloride ions in fresh pore concrete simulating solutions and mortars
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Griffin, Allian Sophia. "Corrosion in New Construction:Elevated Copper, Effects of Orthophosphate Inhibitors, and Flux Initiated Microbial Growth." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/76951.
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It is generally acknowledged that a variety of problems affecting aesthetics, health, and corrosivity of potable water can arise during installation of building plumbing systems. These include 'blue water', microbial infestation, and rapid loss of disinfectant residual, among other things. Frequently cited causes of the problems include metallic fines left in the plumbing lines from deburring, cutting and product fabrication; solder flux residuals (water soluble and petroleum based flux); and solvents for CPVC. Mechanistically, some materials such as flux contain high chloride, high ammonia and cause low pH, which can increase the corrosivity of water held in the lines. Indirect effects are also suspected to be important. For example, ammonia from flux and organic carbon from flux or PVC solvents can spur microbial growth, which in turn can reduce pH or otherwise increase corrosivity. Recent work has also demonstrated that problems with lead leaching to water from brass in modern plumbing can actually be worse in PVC/plastic than in copper systems, if certain types of microbes such as nitrifiers proliferate and drop pH. Some of the problems initiated by construction practices can persist indefinitely, causing higher levels of lead and copper in water, or longer term, contributing to failures of the plumbing system.
Blue water from high copper concentrations is a confounding problem that continues to arise in some locales of the United States. One public elementary school in Miami Dade County is experiencing blue water issues as manifested by blue ice cubes and sink staining. In addition to the aesthetic problems, copper levels are above the EPA's Copper Action Level of 1.3 ppm. Bottled water has been substituted for tap water consumption, which has created a financial burden. The pH of the school's water ranges from 7.15 - 7.5 and the school itself is located 1 ½ miles off the main distribution line resulting in a very low chlorine residual of between 0.06 mg/L Cl2 and 0.18 mg/L Cl2. On site water was shipped to Virginia Tech from Miami to be used in this study. Preliminary testing showed that an increase in the pH of the water would decrease copper leaching. Several pH's were tested which revealed that increasing the pH of the water to 8.5 would drop copper below 1.3 mg/L. When these recommendations were implemented at the school, the high alkalinity and calcium rich water caused calcite scales to form which clogged the chemical feed nozzles. Further bench scale testing indicated that adding 2 mg/L orthophosphate corrosion inhibitor would effectively decrease copper to a level that would comply with the EPA's Copper Action Limit.
Orthophosphate corrosion inhibitors are used by utilities to limit lead and copper corrosion from consumer's plumbing. An evaluation comparing the effects of both 100% orthophosphate inhibitor and orthophosphate/polyphosphate inhibitor blends was performed to study the effects they have on galvanic corrosion, metallic corrosion, microbial growth and the decay of chloramine disinfectant. On site water was sent to Virginia Tech from UNC for use in this bench scale study. The results from this study indicated that 100% orthophosphate inhibitor was the most effective corrosion inhibitor at decreasing metallic corrosion.
It has long been known that microbial activity can have significant effects on water quality. This study evaluated nitrifying and heterotrophic bacterial growth in water systems containing copper pipes, a common plumbing product, and flux which is used in soldering copper pipes together in new construction. There are several types of commercially available fluxes which are often used when soldering new pipes together. Flux ingredients vary and can include extremely high concentrations of ammonia, zinc, chloride, tin, copper and TOC. Flux containing high amounts of ammonia can be detrimental to water quality because it can accelerate the occurrence of nitrification, thus creating a cascading set of problems including, but not limited to, pH decrease and copper corrosion. The results from this case study indicated that flushing a pipe system can effectively decrease the high concentrations of flux present in a new construction system; however, high levels of ammonia from flux can create an environment in which nitrifiers may proliferate within the system.
Many water utilities in the United States are switching disinfection type from chlorine to chloramine due to the increased stability, longer residual time, and overall safety benefits of chloramine. Although chloramines have been found to be a desirable means for disinfection, chloramine decay is an issue of great concern because if the chloramine residual decays, it can leave a water system unprotected against microbial infestation. A preliminary examination of this issue was performed in a laboratory setting to evaluate the many components that effect the stability of chloramine decay, including alkalinity, phosphate, temperature, and various pipe materials. The results from this experiment revealed that temperature increase, pH increase, and aged tygon tubing all accelerated the rate of chloramine decay.Master of Science
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Guo, Xiaolei. "Corrosion inhibition of aluminum alloy 2024-T3 based on smart coatings, hybrid corrosion inhibitors, and organic conversion coatings." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461188604.
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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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Klomjit, Pitichon. "Characterization of Inhibition and Leachability of Corrosion Inhibitors in Commercial Primer Systems." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429291171.
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Chen, Yue. "Inhibition mechanisms of corrosion inhibitors in multiphase flow conditions using electrochemical techniques." Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1179168537.
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Zemajtis, Jerzy. "Modeling the Time to Corrosion Initiation for Concretes with Mineral Admixtures and/or Corrosion Inhibitors in Chloride-Laden Environments." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30721.
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The application of a mineral admixture, or a corrosion inhibitor, or a combination of both are methods used for the corrosion protection for reinforced concrete bridges. The results of a study on evaluation of corrosion inhibitors from three different manufacturers and of concretes with fly ash, slag cement, and silica fume and a concrete with silica fume and a corrosion inhibitor are presented. The specimens were built to simulate four exposure conditions typical for concrete bridges located in the coastal region or inland where deicing salts are used. The exposure conditions were horizontal, vertical, tidal, and immersed zones. The specimens were kept inside the laboratory and were exposed to weekly ponding cycles of 6% (w/w) sodium chloride solution. In addition, cover depth measurements from 21 bridge decks and chloride data from 3 bridge decks were used, together with laboratory data, in modeling the service lives of the investigated corrosion protection methods.
The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates (3LP). Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces.
Modeling the time as a function of probability of the end of functional service life (EFSL) is presented. It has been shown that the distributions of surface chloride concentration, C0, and diffusion coefficient, Dc, are key elements in the model. Model predictions show that the concretes with mineral admixtures provide much better level of protection against moisture and chlorides than the ordinary portland cement concrete alone. Application of a corrosion inhibitor causes an elevation of the chloride threshold resulting in an additional increase in time to EFSL.
More field studies are needed to better estimate distributions of surface chloride concentration and diffusion coefficient of Virginia bridge decks, and to confirm predicted times to EFSL for low permeable (LP) concretes.Ph. D.
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Chiter, Fatah. "Étude théorique d'inhibiteurs verts de corrosion : adsorption de la 8-hydroxyquinoléine sur surfaces d'aluminium." Thesis, Toulouse, INPT, 2015. http://www.theses.fr/2015INPT0113/document.
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Les composés à base de chrome hexavalent sont industriellement utilisés pour inhiber la corrosion des alliages d'aluminium. Ils sont reconnus comme étant des inhibiteurs de corrosion très efficaces et permettent de renforcer les propriétés inhibitrices de la couche d'oxyde formée naturellement sur la surface en présence d'oxygène dans un environnement favorable. Cependant ces composés sont toxiques et cancérigènes. Ils doivent être éliminés (directives européennes) et remplacés par de nouveaux inhibiteurs de corrosion aussi efficaces mais respectueux de l'environnement. Certaines molécules organiques, biodégradables et non toxiques, pourraient jouer ce rôle. De nombreux travaux expérimentaux ont notamment démontré l'efficacité de la molécule de 8-hydroxyquinoléine (8HQ) pour améliorer la résistance à la corrosion de l'aluminium pur et de l'alliage 2024. Néanmoins, le mécanisme de l'inhibition de la corrosion à l'échelle atomique par cette molécule restait inconnu. Dans ces travaux de thèse, nous avons cherché, à l'aide de calculs de physico-chimie quantique, à identifier des facteurs favorables aux processus d'inhibition. Les propriétés d'inhibition de la corrosion sont directement liées au mécanisme d'interaction et aux phénomènes d'adsorption de ces molécules sur la surface du substrat. Nous avons ainsi étudié l'interaction de la molécule 8HQ et ses dérivés sur une surface Al(111). Les taux de recouvrement choisis ont permis de simuler divers cas, de l'adsorption d'une molécule isolée sur la surface à la formation de couches compactes sur le substrat. Outre la détermination des topologies d'adsorption et des énergies associées, nous avons réussi à déterminer la nature et la force des interactions molécules/substrat, notamment par l'étude de la structure électronique à l'interface hybride inhibiteur/métal. Quelle que soit la forme chimique de la 8-HQ (forme native, tautomère, espèces hydrogénée ou déshydrogénée) nous avons démontré que la couche organique adsorbée sur le métal est stable et fortement chimisorbée. Elle peut former une barrière à la pénétration d'agents agressifs sur la surface du substrat et limiter la réaction cathodique de réduction de l'oxygène. Les résultats obtenus contribuent à une meilleure connaissance des mécanismes d'inhibition de la corrosion de l'aluminium pur et aident à la recherche de nouvelles molécules qui pourraient assurer une protection avec une efficacité optimaleChromates are currently used in the aeronautic industry to inhibit corrosion of aluminum alloys. They are known as very effective. However, these compounds are toxic and carcinogenic. They must be replaced by new efficient environmentally friendly corrosion inhibitors. Organic species that are biodegradable and non-toxic molecules could play this role. Several experimental studies demonstrated the efficiency of the 8-hydroxyquinoline molecule (8-HQ) to improve the corrosion resistance of pure aluminum and of 2024 aluminum alloy. However, the inhibition mechanism by the 8-HQ molecule is not totally understood, particularly at the atomic scale. In this PhD work, we tried, thank to DFT calculations, to identify factors that could be favorable to the inhibition processes. From a general point of view, the corrosion inhibition is directly related to the interaction mechanism and adsorption process of the molecules on the substrate surface. We studied the interaction of the 8-HQ molecule and its derivatives on the Al (111) surface. Various adsorption concentrations on the Al surface, from a single molecule to the formation of compact monolayer were modeled. Besides the determination of adsorption topologies and energies, we have identified the nature and strength of the molecules/substrate interactions by analyzing the electronic structure modification at the inhibitor/metal interface. Whatever the chemical form of the 8-HQ (native form, tautomer, hydrogenated or dehydrogenated species), it was demonstrated that the organic layer adsorbed on the metal is stable and strongly chemisorbed. This layer forms a barrier which could prevent the aggressive species to reach the Al surface and limit the oxygen cathodic reduction. The results contribute to a better understanding of the pure Al inhibition mechanisms and help the search for more efficient inhibitive “green” molecules
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Kashyap, Anusha Venkitachalam. "Effects of water chemistry, temperature, gaseous cavitation & phosphate inhibitors on concrete corrosion." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35788.
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Concrete corrosion has serious societal and economic impacts and is an important concern in a utilityâ s overall corrosion control strategy. Though concrete based pipes and linings are only restricted to the distribution mains, they still make up a large percentage of the drinking water infrastructure at about 17% of its total length. An improved understanding of the corrosion mechanisms involved steps that can be taken to mitigate concrete corrosion are very important. This study examined the role of phosphate chemicals, water chemistry, temperature and gaseous cavitation on the degradation of cement-based pipes and linings. It also provides information for utilities to make informed decisions regarding the use, effectiveness, and application of phosphate corrosion inhibitors relative to concrete corrosion control.
Under low alkalinity and low pH conditions, considered to be highly aggressive in the literature, we noticed very substantial corrosion of concrete in laboratory experiments. At high pH and high alkalinity conditions, the buildup of scale (e.g., calcium carbonate) on the inside of the pipe is the major concern. The addition of phosphate inhibitors strongly influenced both concrete corrosion and scaling. At low alkalinity the addition of zinc orthophosphate or polyphosphate reduced corrosion of concrete. The addition of orthophosphate under low alkalinity conditions increased aluminum leaching and could push aluminum concentrations above the EPA SMCL threshold. At high alkalinity conditions the addition of orthophosphate is highly effective at reducing scaling, and aluminum leaching was not a concern.
The presence of high concentrations of magnesium and silicon could form magnesium aluminum oxyhydroxides and magnesium silicates which could act as a protective scale on the concrete surface. However, this precipitate forms only at pH values above 9.5. The effectiveness of this protective scale in reducing corrosion of concrete was not established unambiguously in this research. Temperature plays a key role in corrosion of concrete. Calcite solubility increases at lower temperatures however at higher temperatures corrosion of concrete increases, which implies that corrosion of concrete is not driven by calcite solubility. At higher alkalinities scaling of concrete is higher at lower temperatures. This indicates that calcite solubility controls scaling of concrete at higher alkalinities. Tests with gaseous cavitation indicate that corrosion of concrete does not increase in the presence of gaseous cavitation. Vaporous cavitation is more detrimental to concrete than gaseous cavitation.
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Smart, A. U. "Industrial boiler system corrosion inhibitors : Studies on the high temperature reactions and properties of aliphatic amines in water." Thesis, University of York, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234970.
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Sheffer, Gregory John Antonelli. "Investigation of Copper Pitting Propensity Using Bench and Field Scale Testing." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/42814.
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A range of techniques designed to monitor copper pitting propensity were applied at two water utilities with known pitting disposition. In addition to traditional approaches including ECorr rise, chlorine decay kinetics, and surface analyses, a novel method was attempted to develop â pitting currentsâ between copper samples exposed to differential flow. This method allowed pitting current, potential, and resistance between â pitsâ and sections of copper pipe to be measured. As part of this evaluation, effects of different corrosion inhibitors and secondary disinfectants were investigated in an attempt to identify water quality modifications that might alleviate copper pitting at each utility.
At a Florida utility where customers were experiencing a severe pitting problem, experiments investigated the effectiveness of corrosion inhibitors including orthophosphate, an orthophosphate-polyphosphate blend, and zinc polyphosphate. Results suggested that zinc polyphosphate provided the greatest likelihood of mitigating copper pitting corrosion, whereas orthophosphate and the orthophosphate-polyphosphate blend actually increased electrochemical indications of pitting. According to theory, orthophosphates can increase pitting intensity if applied in insufficient quantities, whereas cathodic inhibitors, such as zinc, can only reduce corrosion rates. Surface analyses determined that zinc polyphosphate produced the least amount of scale, whereas the control produced the greatest amount. Further, surface analyses also suggested that zinc and phosphorus may behave synergistically during precipitation reactions which decrease copper release. Subsequent testing at Virginia Tech laboratories confirmed that some of the benefits from the zinc polyphosphate product were directly attributed to zinc. Consistent with previous research, pitting propensity of the water in the absence of inhibitor decreased at pH 7.5 relative to pH 8.5 (Marshall, 2004). In addition, higher concentrations of chloramines increased the pitting propensity of the water, although the ratio of chlorine to ammonia had little effect.
Similar experiments were also conducted at a utility in Iowa. Copper pitting has always existed in this area at some low level; however an outbreak of copper pinhole leaks recently occurred that is temporally correlated with high chlorine and chloramine concentrations. Experiments investigated combinations of disinfectant type (free chlorine or chloramines) and corrosion inhibitor (orthophosphate or zinc polyphosphate) in an attempt to decrease pitting propensity. Results indicated that the addition of zinc polyphosphate decreased pitting propensity in free chlorine systems as well as systems dosed with chloramines. In contrast, the addition of orthophosphate seemed to be ineffective in either system. Final surface analyses confirmed that inhibitors performed most effectively in the free chlorine system, whereas no clear benefits were realized in chloramine systems.Master of Science