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Bi, Huichao. "Corrosion protection by paint : cathodic disbonding." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:b92b86b0-abb0-4945-8f07-f394b9e9eb5b.
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This work investigated cathodic disbonding of an unpigmented phenalkamine-cured epoxy coating on mild steel, EC, exposed to 3.5 wt.% NaCl solution. Scanning Acoustic Microscopy (SAM), Scanning Kelvin Probe (SKP), Electrochemical Impedance Spectroscopy (EIS) and optical microscopy have been combined to conduct this study. Several factors affecting the cathodic disbonding process: Film thickness, Cation mobility, Electrolyte concentration, Temperature, Paint composition, Polarisation and Open circuit potential, have been investigated. SAM results show that the disbonding of EC with a linear scribe spreads outwards from the defect with blisters forming at the anodes (as shown in SKP potential maps) within the disbond. The disbonded region does not correspond to complete adhesion loss as verified by peel-testing. Semi-immersion tests show that disbonding under full- and semi-immersion conditions have similar behaviours and both follow parabolic kinetics indicating the disbonding is likely to be controlled by a transport process along the coating/metal interface. An intact epoxy coated mild steel panel coupled with bare mild steel shows that the cathodic reaction beneath the coating obeys Tafel law. A mathematical model simulating cathodic disbonding which produces realistic potential files and shows the oxygen reduction is mostly located near the disbond mouth has been developed.
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Riemer, Douglas P. "Modeling cathodic protection for pipeline networks." [Gainesville, Fla.] : University of Florida, 2000. http://etd.fcla.edu/etd/uf/2000/ane5967/Dissertation.pdf.
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Thesis (Ph. D.)--University of Florida, 2000.Title from first page of PDF file. Document formatted into pages; contains xxii, 263 p.; also contains graphics. Abbreviated abstract copied from student-submitted information. Vita. Includes bibliographical references (p. 252-262).
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AL-Shareefi, Hussein. "Neutral network corrosion control by impressed cathodic protection." Thesis, Högskolan Dalarna, Maskinteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:du-4258.
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Shi, Wei. "The effect of intermittent cathodic protection on corrosion protection in the intertidal zone." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-effect-of-intermittent-cathodic-protection-on-corrosion-protection-in-the-intertidal-zone(80f890c7-2498-4c7d-899e-76a80639ac1b).html.
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As an important technique for corrosion control in marine environment, Cathodic Protection (CP) should be applied with a full understanding of environmental conditions and a good consideration of current requirements. Early studies on different kinds of steel specimens in the intertidal zone show severe corrosion losses. Nevertheless, there is evidence that CP can work in these regions of a steel structure because electrolyte pathway can remain some time on thin wetted surfaces when tides recede. This research aims to study corrosion activities and their behaviour under the influence of CP in a thin layer of electrolyte as a simulation of the inter-tidal zone. By means of a mechanical vibrating probe, Scanning Vibrating Electrode Technique (SVET) may be used to study local activities at coating defects in a thin electrolyte layer. The effect of CP on the local currents at the defect site was confirmed by SVET and, significantly, the development of calcareous films under these conditions in seawater was also observed. Such films are found to be effective in the absence of cathodic polarisation and only failed after damage. In order to explore the performance of applying CP, a Finite Element (FE) model of electrically connected zinc and steel samples beneath a specific thickness of electrolyte has been created, with full polarisation curves implemented for each metal based on experimental results obtained. The influence of the electrolyte conductivity and the geometry of the electrodes has also been considered. A comparison can then be made between experimental investigation and computational modelling of this corrosion cell. Epoxy-coated and uncoated mild steel samples obtained in the simulated tidal facility were also investigated. The formation of calcareous films was confirmed. Calcareous films were protective under these intermittent wetting conditions. Techniques used to understand the performance include optical observation, Scanning Electron Microscopy (SEM) together with Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) analysis.
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Oleiwi, H. M. "Using cathodic protection to control corrosion of reinforced concrete structures." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/47895/.
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Cathodic protection (CP) has been increasingly used on reinforced concrete structures to protect steel reinforcement from corrosion. However, due to the complexity of environmental conditions, the specifications in national and international standards are still open to discussion in engineering practices for their accurate suitability. To some extent, the design aspects are still based on practical experience. It implies a great deal of estimations and assumptions. The research conducted in the thesis aims to address some of these challenges. To obtain reliable experimental results, the present study at first investigated the influence of experimental methods on the measurement of concrete electrical resistivity. It studied the effect of alternative current (AC) frequency, electrode materials and electrode configuration. Based on the results, an optimised method was decided for all the series of the experimental tests in this study. The CP study consists of two major works. The first one was to investigate the chloride contaminated concrete exposed to atmospheric condition. Impressed constant current method was adopted for the operation of CP. A series of electrical and electrochemical measurements were conducted for concrete resistivity, corrosion potential, corrosion rate, degree of polarization, instant-off potential and four-hour potential decay. An evaluation on the current adopted criterion in standards has been carried out on the experimental results. The second work was to investigate the corrosion of rebar in concrete specimens submerged (fully and partially) in salty water. For such more corrosive environment, a comparison between the impressed CP operation using constant current and that using constant potential has been conducted. The experiments evaluated the effects of the two major environmental factors, i.e. water and chloride contents, on reinforced concrete durability. The work provided a deep understanding on the electrochemical behaviour of the reinforced concrete system and effectiveness of CP implementation under severe conditions. The research work has an important contribution to fundamental science of corrosion and reinforced concrete deterioration, and the technology and practical application of CP for reinforced concrete structures. The main results of this work indicate the important influence of the frequency and electrode configuration on the electrical resistance measurement. For the reliability of electrical resistivity measurement, a high frequency of 10,000 Hz and an internal carbon fibre electrode method are recommended. Regarding the CP for the chloride contaminated reinforced concrete exposed to the atmosphere, it is suggested that adopting an instant-off potential of -500 mV with respect to Ag/AgCl/0.5KCl reference electrode can provide sufficient protection for the reinforced concrete of up to 0.59 % total chloride by weight of concrete, or concrete resistivity is greater than 6.7 kΩ.cm. Furthermore, it was found that the 100 mV depolarization criterion for the evaluation of CP performance gives an overestimated protection. A depolarization of 50 mV is therefore proposed. In terms of the submerged specimens, the results showed that the water content and chloride content should be explicitly related to the corrosion state rather than through a single parameter of the concrete resistivity for the complicated situations because the water content will affect the oxygen transportation in concrete, and the oxygen availability at the rebar surface will play an important role in the corrosion process, and this is unassessable by concrete resistivity. Moreover, 4 or 24 hours for the 100 mV depolarisation criterion in standards is not applicable for CP assessment where concrete structures are fully submerged due to the low availability of oxygen. On the other hand, the depolarization criterion can be used if the specimens are partially submerged, but different parameters affect the depolarization value such as the magnitude of the applied protection current or potential, chloride concentration, oxygen availability and time of depolarization.
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Trille, Christophe. "Reliability analysis for subsea pipeline cathodic protection systems." Thesis, Cranfield University, 1996. http://dspace.lib.cranfield.ac.uk/handle/1826/12142.
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Subsea pipelines, as the main transportation means for oil and gas produced offshore, are a key element of the production system. Cathodic protection systems (CPS) are used in combination with surface coatings to protect the pipeline from external corrosion. Although cases of pipeline failure due to external corrosion remain rare, such failures can have catastrophic effects in terms of human lives, environment degradation and financial losses. The offshore industry was led to the use of risk analysis techniques subsequent to major disasters, such as Piper Alpha and Alexander Kjelland. These accidents made the development and use of risk analysis techniques of highly significant interest, and reliability analysis is presently becoming a more important management tool in that field for determining reliability of components such as pipelines, subsea valves and offshore structures. This research is based on an analysis of subsea pipeline cathodic protection systems and on a model of the electrochemical potentials at the pipeline surface. This potential model uses finite element modelling techniques, and integrates probabilistic modules for taking into account uncertainties on input parameters. Uncertainties are used to calculate standard deviations on the potential values. Based on the potentials and potential variances obtained, several parameters characteristic of the cathodic protection system reliability, such as probability of failure and time to failure, are calculated. The model developed proved suitable for simulating any pipeline, under any environmental and operational conditions. It was used as a reliability prediction tool, and to assess the effects of some parameters on the cathodic protection system reliability.
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Allison, Crispin. "Flexible liners for corrosion protection of pipelines." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7388.
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Flexible plastic liners are sometimes installed into new and existing oil and gas pipelines to prevent corrosion of the pipe wall. A practical difficulty of this method is that the plastic liners are permeable to gases, which can collect and form an annular space between the liner and the pipe. If the operating pressure in the pipe decreases then the collected gas can cause the liner to collapse and block the pipe. One method for overcoming this problem is to insert vents at intervals along the liner to allow the gas to escape into the pipe during depressurisation. However, there is concern that this arrangement might lead to excessive corrosion beneath the vent where the pipe wall is exposed. The rate of corrosion is expected to be controlled by the vent size but this principle needs to be confirmed by experiment. The work described in this thesis is aimed at investigating this corrosion by experiment for a range of conditions typical of oil and gas production. A novel crevice corrosion cell was designed, consisting of an X100 carbon steel plate and a sheet of transparent Perspex, separated by a thin gasket. A small hole in the Perspex simulated a liner vent and allowed carbon dioxide to reach the steel surface. Tests were carried out in 3.5% NaCl solutions saturated with carbon dioxide at 1 bar partial pressure. Corrosion rates along the length of the annular space were measured using the Linear Polarisation Resistance (LPR) technique on pairs of insulated X100 electrodes set into the plate. The corrosion rates within the annular space have been shown to be small compared to those in the bulk solution and to diminish rapidly with distance from the vent. Mathematical modelling, based on the transport of carbon dioxide, is described to explain these findings and support the experimental work. The effectiveness of the LinerVentTM, installed over the vent, in a turbulence pipeline was demonstrated. The benefit of applying cathodic protection within the annular space was also demonstrated. The results are discussed in terms of the fundamental corrosion principles and their practical implications
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Donohoe, C. J. "Corrosion fatigue of a high strength low alloy steel." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322985.
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Williams, Kevin. "Feasibility of Application of Cathodic Prevention to Cracked Reinforced Concrete in Marine Service." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5333.
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Corrosion can take place as chloride ions accumulate above a critical concentration (CT) at the surface of a reinforcing bar inside concrete in marine service. The initiation of corrosion can be delayed by polarizing the steel cathodically, which is known to increase the value of CT. That effect is the basis of the cathodic prevention (CPrev) method to control corrosion of reinforcing steel in concrete. However, concrete cracks are a common occurrence and at cracks, the buildup of chloride ions is accelerated to the extent that CPrev may be less effective. The findings from an ongoing investigation to determine the effectiveness of cathodic prevention on cracked concrete exposed to a marine environment are presented. Experiments were conducted on reinforced concrete blocks with controlled-width cracks placed along the length of a central reinforcing steel bar. A ponding area on top of each specimen allowed for cyclic exposure to a 5% NaCl solution to imitate a marine environment. Crack widths ranging from 0.01 inch to 0.04 inch and polarization levels ranging from -330 mV to -540 mV were used. The onset of corrosion as a function of time of exposure was determined by measurements of the cathodic current demand needed to reach each target polarization level. The ranking of time to onset of corrosion was used as an indicator to determine how much cathodic prevention is necessary to effectively extend the life of cracked concrete. Results to date suggest that a minimum cathodic polarization level in the range of -540 mV would be needed.
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Alamdari, Mikayil. "Corrosion protection and monitoring of off-shore structures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Oil and gas platforms are confronting a problem of ageing as there are many platforms that were constructed over 40 years ago. Every year, the offshore sector incurs considerable losses due to corrosion. On average, oil and gas companies use 6% of their annual income to fight against corrosion. This all in a short-term has a negative impact on the marine environment and in a long-term endeavour toward sustainable energy encountering difficulties. This thesis presents a novel corrosion inspection method by the implementation of the deep neural network and fuzzy logic models. Fuzzy logic is a suitable mathematical tool for the task since it is capable of handling imprecise information from the real world. The benefit of this approach lies in its ability to include personal experiences and acceptable deterministic models in the calculations. This approach can thus help to reduce the dependence upon the precise data, allow modelling even when a phenomenon is incompletely understood, and lessen the difficulties arising due to the complex computation required by more traditional methods. Moreover, image processing based on algorithms can do the automated inspection of external corrosion phenomena. A complete automated system for corrosion detection in pipelines comprises of a drone to flying over these pipelines and capturing photos and/or videos, and an image based on an algorithm to process these visual data and detect corrosion. The proposed deep learning approach effectively wards off the need for manual inspection and other non-vision based non-destructive evaluation techniques for pipeline corrosion which are cost-ineffective and interrupts the functioning of pipelines. Increased production frequently comes with an unknown cost of the increased rate of material degradation and threatening corrosion failures. Therefore, essential topics as corrosion data management and risk assessment are covered.
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Das, S. C. "Zinc rich paint as anode system for cathodic protection (CP) of reinforced concrete structures and development of corrosion/CP monitoring probes." Thesis, Coventry University, 2012. http://curve.coventry.ac.uk/open/items/5f6b4228-1557-4cf8-bebd-97b5b70bb594/1.
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Since mid-80‟s cathodic protection (CP) has been recognised as the „‟only technique known to stop corrosion regardless of the levels of chloride contamination in concrete‟‟ (FHWA, 1982) and is proved to be the most cost effective means to extend the useful life of the structure. Cathodic protection is an electrochemical technique to stop/mitigate corrosion by supplying „current‟ from an external source in order to suppress the „internally generated‟ current flow due to corrosion processes. The „external‟ current source could be obtained simply by coupling the steel to another electrochemically more active metal, e.g. zinc; alternatively the „external‟ current may be derived from a mains operated low voltage DC power source, viz. transformer/rectifier unit. These two different approaches to supply „external‟ current to stop corrosion are generically termed as: „Sacrificial Anode Cathodic Protection (SACP)‟ system and „Impressed Current Cathodic Protection (ICCP)‟ system, respectively. Both approaches have proved to be feasible, but the impressed current CP system offers greater flexibility with regard to its ability to provide the necessary current in situations where concrete resistivity is relatively high and variable. The sacrificial anode system is most effective if the concrete resistivity is very low or the anode is placed in a very low resistivity environment such as soil with low resistivity, as the inherent driving voltage is low e.g. the potential difference between zinc and corroding steel in concrete is limited to approximately 0.7 volts. Other contra-distinction between the two approaches are that the design life of the sacrificial anode systems are usually range between 10 -15 years; on the other hand the design life of the ICCP systems could be well in excess of 60+ years ( depending on the type of anode system). Page 2 Following the successful application of first CP system, based on impressed current CP (ICCP), on a bridge deck in California, USA 1973, the technology has advanced significantly, particularly the anode systems (which is the main arbiter of a CP system) to deliver the protection current efficiently providing adequate protection (i.e. meeting the criteria recommended in BS EN ISO 12696: 2012 and other International Standards). Most of the CP installations worldwide are operating in ICCP mode. However, due to the escalating cost of anode systems and associated external power supply as well as monitoring/control units for ICCP installation has led researchers to actively pursue different means of developing low cost anode systems. Researchers have mainly focused on sacrificial anode CP (SACP) systems, as SACP does not require an external power supply and control units, but the drawback to this anode system is that it has a shorter life span (usually 10 -15 years compared to 60+ years for ICCP anodes). This work describes the development of an ICCP anode system design utilising commercially available zinc rich paint (ZRP) as a primary anode material offering an innovative but considerably low cost alternative to currently used materials for ICCP anode systems. It also describes the development of a simple and low cost „multifunctional‟ probe for monitoring the performance of the installed CP system, among other functions, such as LPR measurements, macrocell corrosion current measurement, E-log I tests for assessing the current requirements for CP design. For these functions both laboratory investigations and field trial on real life structure were employed.
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Gopalakrishna, Jayashri Sham. "Corrosion protection of advanced surface coatings for decorative applications." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/35042.
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Thesis (PhD) - Swinburne University of Technology, School of Engineering and Science, 2008.A thesis submitted for the degree of Doctor of Philosophy, School of Engineering and Science, Swinburne University of Technology, 2008. Typescript. Includes bibliographical references (p. 189-204).
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Sanchez, Camacho Lizeth J. ""Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection."." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788.
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WANG, QIANG. "The Role of Zinc Particle Size and Loading in Cathodic Protection Efficiency." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2908.
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Metallic additives, also known as anticorrosive pigments, can provide sacrificial cathodic protection and complement the barrier protection afforded by heterogeneous organic coatings to metallic substrates. The unique systematic study of the corrosion resistance of an epoxy coating reinforced with different sizes (80nm, 500nm, 10um) and continuous multiple pigment volume concentration (0, 2%, 10%, 20%, 45%) below global critical pigment volume concentration of zinc particles were studied. The thesis is developing the fundamental understanding to optimize corrosion protection and predicting the protection with time. The properties of these cathodic coatings were investigated by a single-frequency electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) measurements that can be used as to understand cathodic protective state. Finite Element Analysis (FEA) has been applied here for modeling and simulating part of actual experiments. This thesis will help understanding the sensitivity and efficiency to various size and loading of metallic additives for corrosion protection.
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Jeffers, Kenneth E. "Electrochemical impedance spectroscopy for the characterization of corrosion and cathodic protection of buried pipelines." [Florida] : State University System of Florida, 1999. http://etd.fcla.edu/etd/uf/1999/amj9949/jeffers.pdf.
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Thesis (M.S.)--University of Florida, 1999.Title from first page of PDF file. Document formatted into pages; contains xx, 206 p.; also contains graphics. Vita. Includes bibliographical references (p. 202-205).
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Merten, Bobbi Jo Elizabeth. "Embedded Reference Electrodes for Corrosion Potential Monitoring, Electrochemical Characterization, and Controlled-Potential Cathodic Protection." Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26489.
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A thin wire Ag/AgCl reference electrode was prepared using 50 μm Ag wire in dilute FeCl3. The wire was embedded beneath the polyurethane topcoat of two sacrificial coating systems to monitor their corrosion potential. This is the first report of a reference electrode embedded between organic coating layers to monitor substrate health.
The embedded reference electrode (ERE) successfully monitored the corrosion potential of Mg primer on AA 2024-T3 for 800 days of constant immersion in dilute Harrison’s solution. Zn primer on steel had low accuracy in comparison. This is in part due to short circuiting by Zn oxidation products, which are much more conductive than Mg corrosion products. Data interpretation was improved through statistical analysis. On average, ERE corrosion potentials are 0.1 to 0.2 V and 0.2 to 0.3 V more positive than a saturated calomel electrode (SCE) in solution for AA 2024-T3 and steel coating systems, respectively. Further research may confirm that ERE obtains corrosion potential information not possible by an exterior, conventional reference electrode.
The ERE is stable under polarization. AA 2024-T3 was polarized to -0.95 V vs ERE to emulate controlled potential cathodic protection (CPCP) applications. Polarizations of -0.75 V vs ERE are recommended for future experiments to minimize cathodic delamination.
The ERE was utilized to analyze coating mixtures of lithium carbonate, magnesium nitrate, and Mg metal on AA2024-T3. Corrosion potential, low frequency impedance by electrochemical impedance spectroscopy (EIS), and noise resistance by electrochemical noise method (ENM) were reported. Coating performance ranking is consistent with standard electrochemical characterization and visual analyses. The results suggest anti-corrosion resistance superior to a standard Mg primer following 1600 hours of B117 salt spray. Both lithium carbonate and magnesium nitrate are necessary to achieve corrosion protection. Unique corrosion protective coatings for aluminum could be designed through continued mixture optimization.
The Ag wire ERE has been utilized for the characterization and ranking of experimental coatings on metal substrates. Structural health monitoring and corrosion potential feedback of cathodic protection systems are additional uses. There is some indication that CPCP may be applied by ERE to control the substrate polarization for an organic coating system.
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Bumgardner, Jacob Dharma. "Feasibility of Cathodic Protection in Grouted Post Tensioned Tendons - Exploratory Model Calculations." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5918.
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Recent corrosion related failures of grouted post tensioned tendons, even after the introduction of improved grouts, have led to renewed interest in supplemental or backup means of corrosion control for these systems. A finite element model is presented to explore feasibility of impressed current cathodic protection of strand in grouted tendons. The model examines polarization evolution as function of service time and includes consideration of anode placement and size, grout porosity, pore water alkalinity, electrochemical species diffusivity and applied voltage on the polarization efficacy and durability of such a system. The exploratory model projections suggested that, within the context of the design parameters assumed, an impressed current cathodic protection system installed internally into a grouted duct for the purpose of cathodic protection of steel tensioning strand may be feasible for the case of initially passive steel.
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Reddy, Chandra M. "Improved corrosion protection of aluminum alloys by low temperature plasma interface engineering /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924918.
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Rohaya, Abdul Malek. "Assessment of Chloride Induced Corrosion and Impressed Current Cathodic Protection Conditions in Repaired Reinforced Concrete." Kyoto University, 2018. http://hdl.handle.net/2433/231995.
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Christodoulou, Christian. "Repair and corrosion management of reinforced concrete structures." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13577.
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The durability of concrete structures is affected by a number of factors such as environmental exposure, electrochemical reactions, mechanical loading, impact damage and others. Of all of these, corrosion of the reinforcement is probably the main cause for the deterioration of steel reinforced concrete (RC) structures. Corrosion management is becoming increasingly necessary as a result of the growing number of ageing infrastructure assets (e.g. bridges, tunnels etc.) and the increased requirement for unplanned maintenance in order to keep these structures operational throughout their design life (and commonly, beyond). The main RC repair, refurbishment and rehabilitation approaches generally employed can be broadly categorised under a) conventional, b) surface treatments, c) electrochemical treatments and d) design solutions. The overarching aim of this research was to identify the key corrosion management techniques and undertake empirical investigations focused on full-scale RC structures to investigate their long-term performance. To achieve this, individual research packages were identified from the above broad five approaches for repair, replacement and rehabilitation. These were 1) Patch repairs and incipient anodes, 2) Impressed Current Cathodic Protection, 3) Galvanic Cathodic Protection and 4) Hydrophobic treatments. The selection of the above research packages was based on past and present use by the construction industry to repair, refurbish and rehabilitate RC structures. Their contributions may be broadly categorised as i) Investigations on how specific treatments and materials perform, ii) Investigations on the effectiveness of existing methods of measurements and developing alternatives, iii) Changes to the existing theory of corrosion initiation and arrest and iv) Changes to management framework strategies. The key findings from each research package can be summarised as follows: Macrocell activity appears to be a consequence rather than a cause of incipient anode formation in repaired concrete structures, as has previously been presented; ICCP has persistent protective effects even after interruption of the protective current; Discrete galvanic anodes installed in the parent concrete surrounding the patch repair are a feasible alternative to galvanic anodes embedded within the patch repairs of RC structures; Silanes may have a residual hydrophobic effect even after 20 years of service.
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Costa, Carina Guedes da. "Control of cathodic reactivity via active protective layers." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/21533.
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Mestrado em Engenharia de MateriaisO presente trabalho encontra-se dividido em quatro subtópicos: (1) Design do suporte para as amostras, (2) a escolha do inibidor e do tipo de revestimentos, (3) a incorporação dos nanocontentores nos revestimentos e por fim (4) a avaliação da eficiência dos sistemas criados. O suporte das amostras acopladas foi concebido tendo em conta o efeito galvânico entre as duas amostras. Os revestimentos a utilizar foram escolhidos epóxi e sol-gel A principal função destes revestimentos ´inteligentes´ é proteger liga de aluminio 2024 da corrosão, quando está acoplada galvanicamente com o polímero reforçado com fibras de carbono (CFRP). Em cada revestimento foram incorporados dois tipos de nanocontentores, LDH Mg/Al e Bentonite, carregados com o respectivo inibidor. Os nanocontentores LDH foram carregados com um inibidor orgânico 1,2,3-benzotriazole. No caso dos nanocontentores de bentonite o inibidor incorporado foi Ce(NO)3. A incorporação dos nanocontentores foi realizada por via mecânica por forma a obter uma maior homogeneidade. A liga de alumininio foi submetida a um pré – tratamento ( Socosurf ) e o polímero reforçado com fibras de carbono foi aplicado um prétratamento de Plasma pressão atmosférica. Por forma a avaliar a eficiência e propriedades anticorrosivas quer dos revestimentos quer dos inibidores, foram utilizadas as técnicas de caracterização: espectroscopia de impedância electroquímica (EIS), microscopia ótica, testes de adesão e teste de nevoeiro salino (SST). O trabalho foi realizado em ambiente industrial (Airbus Group Innovations).
This work is divided into four sub-topics: (1) Design support for the samples; (2) the choice of the inhibitor and the type of coating, (3) the incorporation of nanocontainers in coatings and lastly (4) the efficiency of the chosen systems. The support of the coupled samples was designed to prove the galvanic effect between the two samples. Taking into account, the coatings were chosen using epoxy and sol-gel, the function of these "smart" coatings is to protect aluminum 2024 alloy, when electrically coupled to carbon fiber reinforced plastic (CFRP), against corrosion. In each coating two types of nanocontainers were incorporated, LDH Mg / Al and Bentonite, loaded with the respective inhibitor. The LDH nanocontainers were loaded with an organic inhibitor 1,2,3-benzotriazole. In the case of Bentonite nanocontainers the embedded inhibitor was Ce (NO)3. The incorporation of nanocontainers was accomplished through mechanical stirring in order to achieve greater uniformity. On the aluminum alloy and on the carbon fiber reinforced plastic a pre-treatment (Socosurf) and a pretreatment Atmospheric Pressure Plasma, respectively were applied. In order to test the efficiency and anticorrosive properties of the coating and inhibitors, electrochemical impedance spectroscopy (EIS), optical microscopy, adhesion test and salt spray test (SST) were used. The work was carried out in an industrial environment (Airbus Group Innovations).
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Walsh, Michael Thomas. "Corrosion of Steel in Submerged Concrete Structures." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6048.
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This investigation determined that severe corrosion of steel can occur in the submerged portions of reinforced concrete structures in marine environments. Field studies of decommissioned pilings from actual bridges revealed multiple instances of strong corrosion localization, showing appreciable local loss of steel cross-section. Quantitative understanding of the phenomenon and its causes was developed and articulated in the form of a predictive model. The predictive model output was consistent with both the corrosion rate estimates and the extent of corrosion localization observed in the field observations. The most likely explanation for the observed phenomena that emerged from the understanding and modeling is that cathodic reaction rates under oxygen diffusional limitation that are negligible in cases of uniform corrosion can nevertheless support substantial corrosion rates if the corrosion becomes localized. A dynamic evolution form of the model was created based on the proposition that much of the steel in the submerged concrete zone remained in the passive condition given cathodic prevention that resulted from favorable macrocell coupling with regions of the steel that had experienced corrosion first. The model output also matched observations from the field, supporting the plausibility of the proposed scenario.
The modeling also projected that corrosion in the submerged zone could be virtually eliminated via the use of sacrificial anode cathodic protection; the rate of corrosion damage progression in the low elevation zone above water could also be significantly reduced. Continuation work should be conducted to define an alternative to the prevalent limit-state i.e., visible external cracks and spalls, for submerged reinforced concrete structures. Work should also be conducted to determine the possible structural consequences of this form of corrosion and to assess the technical feasibility and cost/benefit aspects of incorporating protective anodes in new pile construction.
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Holmes, Steven. "An investigation into the practical and theoretical aspects of hybrid cathodic protection." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/12280.
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Galvanic anode technology has in recent years come to the fore as a cost-effective method of successfully mitigating the corrosion of reinforcing steel in concrete structures. Developments in the field of cathodic protection have included the introduction of a novel Hybrid anode system, which uses the same sacrificial anode to pass a short-term impressed current before being connected to the steel directly to provide a long-term galvanic current. Galvanic and hybrid technologies are often seen as less powerful solutions in the treatment of reinforcement corrosion, and the test methodologies which determine the efficacy of cathodic protection systems favour impressed current technologies. The work completed has investigated the application of traditional and novel corrosion assessment techniques to laboratory samples to assess the protection offered by the hybrid treatment methodology in both treatment phases. In addition, the response of both galvanic and hybrid anodes to environmental conditions has been recorded and assessed before being discussed in the context of steel protection criteria. Finally, an investigation is presented into the on-site deterioration of commercially pure titanium feeder wire installed as part of the hybrid anode system and potential solutions to the problem have been documented. The research undertaken found that the hybrid anode system is capable of protecting steel in challenging, aggressive environments. This was confirmed by steel corrosion rate and indicative steel potential measurements. The responsive behaviour investigation showed that the current output of galvanic and hybrid anodes responds rapidly to changes in the corrosion risk posed to the steel and that this has a direct effect on anode system lifetimes. An assessment of the polarisation-based protection criteria applied to steel in concrete has found that the standard inhibits the use of responsive behaviour, and that revisions which consider the present risk of steel corrosion by considering the corrosion current resulting from the relative aggressivity of the concrete environment would be more valid in their application. A cathodic protection system based on the concepts of pit re-alkalisation and pH maintenance can fully utilise galvanic anode responsive behaviour. It was discovered that the deterioration of commercially pure titanium feeder wire seen on site installations was due to anodising in the presence of chloride media which had the potential to lead to pitting corrosion. The pitting risk varied depending on the duration of the treatment and proximity to the installed anode. An anodically grown oxide delayed the onset of corrosion in aqueous KBr solution, but did not significantly increase the pitting potential.
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Olowe, Adedayo Christianah. "Corrosion assessment and cathodic protection design parameters for steel structures in deep and ultra deep offshore waters." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201965.
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Carbon steel finds much application for use in industries including civil; manufacturing; oil and gas; as well as, renewable energy. Common examples for usage of steel include water pipelines; oil pipelines; bridges; etc. The main advantages of steel over other engineering materials are its strength and affordability. However, steel undergoes corrosion which is a degradation mechanism that occurs as a result of the electrochemical interaction between steel and its environment. There are two main options to control corrosion, aside from material selection techniques, namely, the use of protective coating systems to isolate the steel from the environment; or the use of cathodic protection. Cathodic protection involves the use of galvanic anodes or impressed current system to prevent steel corrosion. Currently the oil and gas industry accounts for the major share of consumption of galvanic anodes for the protection of steel in engineering applications. Recent incursions into deep water depths by the Oil and Gas industry in the last decade or so has brought to the fore the need to understand better the performance of steel at deep and ultra deep water depths; as well as to develop an understanding of how cathodic protection works at these water depths. So far, the bulk of industry experience lies in shallow waters and current international cathodic protection design guidelines are based on data collated at these shallow water depths. It is the objective of this research work to assess the corrosion properties of steel with deep seawater parameters and determine design current density requirements for effective cathodic protection of steel at deep and ultra deep water depths offshore.
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Buday, Martin. "Digitálně řízení tyristorový zdroj s GSM komunikací." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400622.
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Content of this diploma thesis is project of the digital control design for a thyristor source with GSM communication. Designed for corrosion protection. The work contain design of the whole device from the initial proposals of the electro diagrams up to finished product. It describes the events that arise in corrosion, explains the principle of operating a thyristor as a power switch. It also describes the creation and structure of a simple menu using the STM32 microprocessor. It explains the principle of controlling a source. Next, it deals with controlled rectifiers using a thyristor.
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Egtvedt, Solveig. "Thermally Sprayed Aluminum (TSA) with Cathodic Protection as Corrosion Protection for Steel in Natural Seawater : Characterization of Properties on TSA and Calcareous Deposit." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16340.
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Cathodic protection is an effective corrosion protection for structures submerged in seawater. In addition to applying the current need to lower the metal below the protection potential, a resulting increase in interfacial pH leads to precipitation of calcareous deposit. This deposited layer act as a barrier against oxygen diffusion on the surface, hence lowering the current demand of the structure. However, this layer will also hinder the thermal conductivity, and is therefore unwanted at the surface of heat exchangers.There are several factors influencing the precipitation of calcareous deposit. This includes potential, current, pH, seawater chemistry, flow rate etc. These factors have been thoroughly investigated for many years, but mostly with steel as substrate material. Specimens of steel coated with thermal sprayed aluminum (AlMg5) and aluminum plates of alloys AA5082, AA1050 and Al99.99 were exposed to seawater for 5-6 weeks, polarized to -1050 mV vs Ag/AgCl. The current demand was constantly recorded using KorrosjonsLogger©. Results from introductory experiments are also included. The unsealed TSA specimens had the highest current demand, but were also exposed to a higher seawater temperature than the other specimens, which has influenced the results. The sealed TSA specimens had a current demand around 10 mA/m2 after 6 weeks, which is 10 times lower than usually found on steel specimens. For the aluminum plates the trend showed that the higher alloying elements, the higher current density.The explanation for the low current demand compared to steel is that the cathodic area for aluminum is the intermetallic particles that are cathodic to the matrix, while for steel the whole surface act as a cathodic site. In addition, mechanisms during cathodic protection of aluminum lead to an isolation of the cathodic particle, hence continuously lowering the current demand.After exposure, the specimens were investigated in SEM and the composition on the surface was found using EDS. The SEM images showed a furry surface on the TSA specimen, but no familiar structure of calcareous deposit, which has been seen on steel specimens. For the aluminum plates, the intermetallic particles had been “dug out”, showing a pit between the particle and matrix. A typical structure of calcareous deposit was not seen here either. However, the EDS analysis showed an increase in both Mg and Ca content. The Mg/Ca ratio varied over the surface, with the highest ratio and content for the intermetallic particles for the aluminum plates and at the peaks of the surface at the TSA specimens. The Mg/Ca ratios found were much higher than found on steel.Both the SEM images and EDS analysis confirms the theory that there will precipitate less calcareous deposit on TSA surfaces compared to steel. Further studies will show whether the small content found will have an influence on the thermal conductivity.
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Moran, Andrew J. "An Assessment of the Susceptibility to Corrosion from Alternating Current of Cathodically Protected Steel Pipelines in Soils." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1590695228893218.
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Duboscq, Julien. "Corrosion des aciers en milieu marin : processus se déroulant dans les zones cathodiques." Thesis, La Rochelle, 2019. http://www.theses.fr/2019LAROS027.
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L’étude des phénomènes se déroulant dans les zones cathodiques représente un enjeu majeur dans la compréhension des mécanismes de corrosion. L’ensemble de ces travaux de thèse repose sur l’étude de la nature, des processus de transformation et du rôle des différents composés présents dans ces zones. La première partie de cette étude concerne les stades initiaux de la formation des couches minérales dans les zones anodiques et cathodiques. Ce premier volet a permis de mettre en évidence la compétition RV(SO42-)/RV(CO32-). Il en ressort, après calculs thermodynamiques, que le pH d’équilibre est très proche du pH de l’eau de mer, ce qui permet d’avancer plusieurs hypothèses sur la prédominance de RV(SO42-) observée dans les couches de produits de corrosion formées en milieu naturel. La deuxième partie de cette étude porte sur la stabilité d’une forme de chukanovite chargée en Fe(III). Une telle chukanovite partiellement oxydée pourrait avoir des propriétés semi-conductrices et pourrait jouer un rôle important dans les processus électrochimiques. Ce travail a cependant démontré qu’un tel composé tendait à se transformer, en conditions anoxiques, en un mélange de chukanovite non oxydée et de magnétite. La chukanovite partiellement oxydée, quelles que soient ses propriétés électriques, ne peut donc pas intervenir dans les processus de corrosion des aciers à long terme. La troisième partie de cette étude porte sur l’influence des ions Mg2+ et de la matière organique sur la formation et la transformation des rouilles vertes. Il en ressort que les ions Mg2+ favorisent RV(Cl-), et très probablement RV(CO32-) qui a la même structure, au détriment de RV(SO42-). A l’inverse, la matière organique semble favoriser la variété sulfatée. La dernière partie de ces travaux a pour objet une double étude in-situ en zone de marnage : en corrosion libre et sous protection cathodique. Le principal résultat de l’analyse des échantillons en corrosion libre montre que l’activité des BSR se concentre initialement dans les zones cathodiques, favorisant la formation de FeS, composé conducteur, dans ces zones. Il en découle que l’influence bactérienne peut donc renforcer le processus auto-entretenu purement abiotique qui tend à favoriser la magnétite (composé conducteur électronique) dans les zones cathodiques et RV(SO42-) dans les zones anodiques. L’étude de la protection cathodique en zone de marnage a montré l’impact combiné du séchage de la surface de la structure protégée et de la distance séparant l’acier émergé de la surface de l’eau. Il s’avère par ailleurs que la composition de la couche minérale pourrait constituer un bon indicateur de l’efficacité de la protection cathodique en zone de marnageThe study of the phenomena occurring in cathodic zones is a major stake in the comprehension of corrosion mechanisms of carbon steel in seawater. This thesis work is based on the study of the nature, transformation processes and role of the different compounds present in these zones. The first part of the study deals with the first stages of the formation of mineral layers in anodic and cathodic zones. The obtained results highlighted the competition between GR(SO42-) and GR(CO32-). A thermodynamic approach showed that the GR(SO42-)/GR(CO32-) equilibrium pH was close to the pH of seawater, and various assumptions could then be forwarded to explain the observed predominance of GR(SO42-) in the corrosion product layers formed in natural seawater. The second part of this study deals with the stability of Fe(III)-containing chukanovite. Such a partially oxidized chukanovite could have semi-conductor properties and could play a role in the electrochemical processes. However, our results showed that Fe(III)-containing chukanovite tended to transform in anoxic conditions, leading to a mix of non-oxidized chukanovite with magnetite. Fe(III)-containing chukanovite, whatever its electrical properties, cannot play a role in the long-term corrosion processes of steel. The third part of this study deals with the influence of Mg2+ ions and organic matter on the formation and transformation of green rusts. It was observed that Mg2+ ions promoted the formation of GR(Cl-), and more likely of GR(CO32-) that has the same structure, at the detriment of GR(SO42-). Conversely, organic matter seems to favor the sulfate green rust. The final part of this work deals with a double in-situ study in the tidal zone, realized with steel coupons whether immersed unprotected at OCP or set under cathodic protection. The major result obtained with the unprotected coupons showed that SRB activity concentrated initially in the cathodic zones, thus favoring the formation of FeS, an electronic conductor, in these zones. This result demonstrates that biological activity can increase the effects of the purely abiotic process that favors the formation of magnetite (electronic conductor) in the cathodic zones and GR(SO42-) in the anodic zones. The study of cathodic protection in the tidal zone showed the combined influence of the drying of the emerged steel surface and the increase of the distance between the emerged steel surface and the seawater level. The composition of the mineral layer covering the metal surface could be an indicator of the effectiveness of cathodic protection in the tidal zone
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Yang, Yuan Feng. "Calcium and magnesium containing anti-corrosion films on mild steel." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/calcium-and-magnesium-containing-anticorrosion-films-on-mild-steel(34a7b76f-8ba6-49a7-a1fa-d87f52dc230f).html.
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Under normal conditions, cathodically protected mild steel in seawater is protected by a precipitated film of calcium carbonate and magnesium hydroxide, the so-called calcareous film. This study has attempted to investigate the dynamics of calcareous deposit formation during cathodic protection and the composition of calcareous deposits formed under different applied current densities, and also the role played by the initial current density in forming a good quality calcareous deposit. In addition, an under protection situation can occur where current demand values are under estimated, or where structures are approaching the end of their design lives. In these conditions, a calcareous film might well occur but complete protection is probably not possible. These situations have also been studied. At low insufficient current densities where steel corrosion is still occurring, a clear correlation exists between the iron containing corrosion product and the overlaying magnesium hydroxide layer. Such effects have also been investigated using pH titration analysis, where the effect of co-precipitation of the iron and magnesium oxides/hydroxides has been shown. At higher current densities a layered precipitate has been shown to occur consisting of an inner magnesium containing layer and an outer calcium containing layer. At obvious overprotection current densities, the mechanical stresses involved in hydrogen evolution are assumed to give rise to film cracking. To augment and compliment the study on calcareous calcium/magnesium films formed during cathodic protection, a calcium-magnesium containing pigment has also been investigated in aqueous solutions at open circuit as a possible corrosion inhibitor. Another study looked at the same inhibitor in conjunction with a sacrificial zinc anode. Very effective inhibition has been shown with the film containing not only magnesium, calcium and phosphorous but also zinc. In all the investigations electrochemical methods have been used together with various surface analytical techniques.
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Sassine, Elie. "Protection cathodique du béton armé par revêtement electro-conducteur autonome." Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0007/document.
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La protection cathodique par courant imposé (PCCI) est l’une des techniques adoptées pour limiter ou annihiler la corrosion dans le béton armé. Le but de cette thèse est de développer des revêtements suffisamment conducteurs et autonomes pour s’affranchir de l’utilisation des anodes primaires métalliques lors de la PCCI. Ce mémoire est formé de quatre parties principales :I. La première partie résume la recherche bibliographique réalisée. II. Cette partie sera consacrée à la formulation des revêtements électro-conducteurs par dispersion des poudres-pigmentaires conductrices (métallique ou carbone) dans une résine acrylique ou polyuréthane. III. L’efficacité des revêtements électro-conducteurs en tant qu’anode autonome est étudiée dans cette partie. IV. La dernière partie présente des essais de PCCI réalisés en continu pendant 6 mois sur des dallettes corrodées. Des spécimens témoins non corrodés sont aussi placés dans le même environnement sans protection cathodiqueImpressed Current Cathodic Protection (ICPP) is one of the electrochemical techniques applied to limit or annihilate corrosion. The aim of this thesis is to develop sufficiently conductive and autonomous coatings to overcome the use of primary anodes during ICPP. This thesis is based on four main parts:I. The first part summarizes a bibliographic review of corrosion in reinforced concrete. II. This part will focus on the formulation of electroconductive coatings by mixing conductive powders (metallic or carbon) with an acrylic or polyurethane resin. III. The effectiveness of electroconductive coatings as an autonomous anode is studied in this section. IV. The last part presents ICCP tests carried out continuously for 6 months on corroded slabs. Non-corroded specimens are also placed in the same environment without cathodic protection in order to make a comparative analysis
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Filho, Sergio Eduardo Abud. "Estudo da corrosão por interferência de corrente alternada em estruturas enterradas e desenvolvimento de metodologia para sua detecção." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-21072016-101248/.
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Dutos metálicos revestidos, enterrados e protegidos catodicamente, quando são instalados nas proximidades de linhas de transmissão e distribuição de energia elétrica, vêm apresentando problemas de corrosão, sendo esta atribuída às interferências de corrente alternada dispersas no solo. São muitos os critérios propostos na literatura para verificar se um duto está ou não sujeito a esse tipo de problema, mas tais critérios são contraditórios e ineficientes, uma vez que não levam em conta parâmetros termodinâmicos e não contemplam o acoplamento dos potenciais originados de corrente contínua com os potenciais oriundos de corrente alternada. O objetivo do presente trabalho foi estudar a corrosão causada por corrente alternada, selecionar um critério seguro de verificação da probabilidade de ocorrência dessa corrosão e desenvolver uma nova metodologia para a obtenção dos parâmetros necessários para a aplicação do critério proposto. Com base em uma ampla pesquisa bibliográfica, em resultados experimentais obtidos em laboratório e em campo, foi possível a seleção do seguinte mecanismo: a corrosão por corrente alternada é decorrente da oscilação do potencial da interface duto/solo que, dependendo do valor do pH nas suas vizinhanças, leva o sistema alternadamente ao domínio da corrosão e da imunidade ou alternadamente ao domínio da formação de óxidos (com e sem passivação) e da imunidade. Nessas condições, a corrosão do aço-carbono ocorre devido à irreversibilidade da reação Fe2+ + 2e- Fe, nos casos de alcalinização limitada, e à impossibilidade de formação de uma camada passiva protetora decorrente da flutuação de potencial entre o domínio de formação de óxidos e da imunidade, nos casos de alcalinização moderada. Como critério de verificação da ocorrência ou não de interferência de corrente alternada em dutos enterrados e catodicamente protegidos foi proposta, neste estudo, a obtenção da forma de onda do acoplamento entre os potencias originados de corrente contínua e os oriundos de corrente alternada sem a influência da queda ôhmica e a comparação do potencial de pico dessa forma de onda com o potencial estabelecido como limite aceitável do sistema de proteção catódica tradicional. Esta proposição foi feita com base na termodinâmica, o que garante que a previsão seja usada com mais segurança. Finalmente, foi desenvolvida uma sonda que, juntamente com uma instrumentação adequada, é capaz de fornecer a forma de onda do referido acoplamento em dutos enterrados e catodicamente protegidos, sem a interferência da queda ôhmica.Corrosion problems have been observed in cathodically protected pipelines installed in the vicinity of high voltage power lines or electrical distribution systems. Many of these problems have been attributed to interferences coming from stray alternating currents. In the literature, there are many criteria proposed aiming at verifying the AC corrosion probability. However, such criteria are contradictory and ineffective since they do not take into account thermodynamic parameters and do not include the coupling of potential coming from direct current and the potential due to stray alternating current. The aim of this work was to study pipeline corrosion induced by stray alternating current, to select a safe criterion for the probability of this corrosion and to develop a new methodology for obtaining the required parameters for the application of the selected criterion. A broad literature review and the results obtained from a series of tests and analyses have allowed choosing the following mechanism: AC corrosion is a result of the fluctuation of the pipe/soil potential which, depending on the pH of the soil near the pipe, takes the system alternatively to the corrosion and to the immunity domains or alternatively to the oxide formation (with or without passivation) and to the immunity domains. Under these conditions, the corrosion of carbon steel occurs due to the irreversibility of the reaction Fe2+ + 2e- Fe reaction in cases of limited alkalinization and due to the impossibility of forming a protective passive layer caused by the potential fluctuation between the oxide formation and the immunity domains in cases of moderate alkalinization. In this study, a method to obtain the waveform of the AC+DC potential, without the ohmic drop, was proposed. The comparison of the peak potential of the AC + DC waveform with the potential value established as an acceptable threshold for traditional cathodic protection systems was used as a criterion for AC corrosion assessment. This criterion is proposed based on thermodynamic principles which ensure that the prediction is reliable. Finally, a probe was developed. This probe, along with a proper instrumentation, is able to provide the desired waveform for a safe application of the proposed criterion.
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Wang, Xi. "Corrosion Protection of Aluminum Alloy 2024-T3 by Al-Rich Primer." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557143060015145.
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Kidd, Jr Michael Scott. "Al-Ga Sacrificial Anodes: Understanding Performance via Simulation and Modification of Alloy Segregation." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/89066.
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Marine structures must withstand the corrosive effects of salt water in a way that is low cost, reliable, and environmentally friendly. Aluminum satisfies these conditions, and would be a good choice for a sacrificial anode to protect steel structures if it did not passivate. However, various elements can be added to aluminum to prevent this passivation. Currently, Al-Ga alloys are used commercially as sacrificial anodes but their performance is not consistent. In this research, Thermo-Calc software was used to simulate various aspects of the Al-Ga system in an attempt to understand and potentially correct this reliability issue. Simulations showed that gallium segregates to the grain boundaries during solidification and then diffuses back into the grains during cooling to room temperature. Simulations also suggest that faster cooling rates and larger grains cause the potential segregation of gallium at the grain boundaries to remain after cooling. A set of aluminum plus 0.1% weight percent gallium alloy plates were produced with varying cooling rates, along with a control set (cooled slowly in a sand mold). Some samples were later homogenized via annealing. Samples were subjected to a 168 hour long galvanostatic test to assess voltage response. The corrosion performance of samples was found to have both consistent and optimal voltage range when subjected to quick cooling rates followed by annealing. Testing samples at near freezing temperature seems to completely remove optimal corrosion behavior, suggesting that there are multiple causes for the voltage behavior.Master of Science
Ships must withstand the corrosive effects of salt water in a way that is low cost, reliable, and environmentally friendly. Aluminum has properties which could allow a plate of it to rust instead of a ship it is attached to, thus protecting the ships from rusting. However, because aluminum usually does not rust, gallium can be added to aluminum to allow it to rust. Currently, aluminum-gallium alloys are used commercially to protect ships, but their performance is not consistent. In this research, various aspects of the aluminum-gallium system were simulated in an attempt to understand and potentially correct this reliability issue. Simulations showed that the gallium concentration may not be uniform in the alloy, and various conditions can cause the gallium concentration to be inconsistent. A set of aluminum-gallium alloy plates were cast in molds from liquid aluminum. Some of the plates were cooled quickly, and some cooled slowly. Some samples were later heated in an oven at high temperatures in an attempt to even out the gallium concentration. Samples were subjected to tests to observe corrosion behavior. The corrosion performance of samples was found to be best when subjected to quick cooling rates followed by the oven heating. Testing the samples in cold temperatures seemed to remove the desired corrosion behavior, suggesting that there are multiple reasons for the inconsistent corrosion behavior of aluminum gallium.
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Kidd, Michael Scott Jr. "Al-Ga Sacrificial Anodes: Understanding Performance via Simulation and Modification of Alloy Segregation." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/89066.
Full textAbstract:
Marine structures must withstand the corrosive effects of salt water in a way that is low cost, reliable, and environmentally friendly. Aluminum satisfies these conditions, and would be a good choice for a sacrificial anode to protect steel structures if it did not passivate. However, various elements can be added to aluminum to prevent this passivation. Currently, Al-Ga alloys are used commercially as sacrificial anodes but their performance is not consistent. In this research, Thermo-Calc software was used to simulate various aspects of the Al-Ga system in an attempt to understand and potentially correct this reliability issue. Simulations showed that gallium segregates to the grain boundaries during solidification and then diffuses back into the grains during cooling to room temperature. Simulations also suggest that faster cooling rates and larger grains cause the potential segregation of gallium at the grain boundaries to remain after cooling. A set of aluminum plus 0.1% weight percent gallium alloy plates were produced with varying cooling rates, along with a control set (cooled slowly in a sand mold). Some samples were later homogenized via annealing. Samples were subjected to a 168 hour long galvanostatic test to assess voltage response. The corrosion performance of samples was found to have both consistent and optimal voltage range when subjected to quick cooling rates followed by annealing. Testing samples at near freezing temperature seems to completely remove optimal corrosion behavior, suggesting that there are multiple causes for the voltage behavior.Master of Science
Ships must withstand the corrosive effects of salt water in a way that is low cost, reliable, and environmentally friendly. Aluminum has properties which could allow a plate of it to rust instead of a ship it is attached to, thus protecting the ships from rusting. However, because aluminum usually does not rust, gallium can be added to aluminum to allow it to rust. Currently, aluminum-gallium alloys are used commercially to protect ships, but their performance is not consistent. In this research, various aspects of the aluminum-gallium system were simulated in an attempt to understand and potentially correct this reliability issue. Simulations showed that the gallium concentration may not be uniform in the alloy, and various conditions can cause the gallium concentration to be inconsistent. A set of aluminum-gallium alloy plates were cast in molds from liquid aluminum. Some of the plates were cooled quickly, and some cooled slowly. Some samples were later heated in an oven at high temperatures in an attempt to even out the gallium concentration. Samples were subjected to tests to observe corrosion behavior. The corrosion performance of samples was found to be best when subjected to quick cooling rates followed by the oven heating. Testing the samples in cold temperatures seemed to remove the desired corrosion behavior, suggesting that there are multiple reasons for the inconsistent corrosion behavior of aluminum gallium.
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Dugarte, Margareth. "Polarization of Galvanic Point Anodes for Corrosion Prevention in Reinforced Concrete." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3466.
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The polarization performance of two types of commercial galvanic point anodes for protection of reinforced steel around patch repairs was investigated. Experiments included measurement of the polarization history of the anode under constant current impressed by galvanostatic circuits and in reinforced concrete slabs. The tests revealed, for both types of anodes, a potential-current function (PF) indicating relatively little anodic polarization from an open circuit potential at low current levels, followed by an abrupt increase in potential as the current approached an apparent terminal value. Aging of the anodes was manifested by a continually decreasing current output in the concrete tests, and by increasingly more positive potentials in the galvanostatic tests. Those changes reflected an evolution of the PF generally toward more positive open circuit potentials and, more importantly, to the onset of elevated polarized potentials at increasingly lower current levels. There was considerable variability among the performance of replicate units of a given anode type. Modest to poor steel polarization levels were achieved in the test yard slabs. Modeling of a generic patch configuration was implemented with a one-dimensional approximation. The model calculated the throwing distance that could be achieved by a given number of anodes per unit perimeter of the patch, concrete thickness, concrete resistivity, amount of steel and amount of polarization needed for cathodic prevention. The model projections and aging information suggest that anode performance in likely application scenarios may seriously degrade after only a few years of operation, even if a relatively optimistic 100 mV corrosion prevention criterion were assumed. Less conservative criteria have been proposed in the literature but are yet to be substantiated. Other investigations suggest a significantly more conservative corrosion prevention may apply instead. The latter case would question the ability of the point anodes to provide adequate corrosion prevention.
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Guessoum, Khadoudj. "Nouveaux alliages zinc-terres rares pour des applications anticorrosion : élaboration, propriétés et traitements de surfaces." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0071/document.
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De nouveaux alliages Zn-TR1-5 %mass.(TR = Ce, La et Mischmetal : Ce 75%/La25%) ont été synthétisés par fusion sous atmosphère contrôlée et coulés sous forme de plaques. Dans ces nouveaux matériaux, les terre rare sont localisées exclusivement dans des phases intermétalliques dispersées de manière homogène dans la matrice de zinc : Zn11Ce, Zn13La ou Zn11Ce1-xLax and Zn13CeyLa1-y. Le comportement électrochimique de ces nouveaux alliages a été étudié dans un milieu corrosif de référence simulant les conditions atmosphériques. En parallèle, les phases intermétalliques pures Zn11Ce and Zn13La ont été synthétisées et leur influence électrochimique a été évaluée par voltamétrie et couplage galvanique. Les résultats montrent que les deux phases intermétalliques sont des sites cathodiques préférentiels de la réduction du dioxygène et induisent une inhibition cathodique de la corrosion des alliages Zn-TR par rapport au zinc pur. Ce phénomène est plus marqué dans le cas des alliages au lanthane. Dans le cas spécifique des alliages au cérium, une inhibition anodique a également été observée et corrélée avec une modification chimique des produits de corrosion (composés majoritairement d'hydrozincite). En fait, une faible quantitéhomogène de cérium a pu être mise en évidence dans la couche de corrosion par spectrométrie dispersive en longueur d'onde. D'après les résultats d'expériences de précipitation contrôlée de sels de cérium et zinc en milieu carbonaté, la présence de cérium dans la couche de corrosion et son caractère protecteur pourraient être attribués à la formation d'un composé mixte double lamellaire zinc-cérium. L'addition de moins de 2%mass. de cérium ou lanthane permet d'améliorer la résistance à la corrosion du zinc. Cependant, lorsque la teneur en terre-rare augmente, l'effet de couplage galvanique devient plus important et rend les alliages moins résistants que le zinc purNew Zn-RE1-5 wt.% alloys (RE=Ce, La and Mischmetal: Ce 75%/ La 25%) were synthesized by melting under controlled atmosphere and cast in plates. In these materials, rare earth metal are exclusively present in intermetallic phases homogeneously dispersed in the zinc matrix: Zn11Ce, Zn13La or Zn11Ce1-xLax and Zn13CeyLa1-y. The electrochemical behavior of these new alloys was investigated in a reference corrosivemedium. In parallel, the pure intermetallic phases Zn11Ce and Zn13La were synthesized and their electrochemical influence was studied by voltametry and galvanic coupling. Results show that both intermetallic phases act as preferential cathodic sites of dioxygen reduction and induce a cathodic inhibition of the corrosion of the Zn-RE alloys by comparison with pure zinc. This phenomenon is much more significant in the case of lanthanum containing alloys. In the specific case of cerium addition to zinc, an anodic inhibition was also observed and correlated with a chemical modification of the corrosion products (mainly made of hydrozincite). Actually, low quantities of cerium (less than 1 at.%) have been detected homogeneously in the corrosion layer by wave-length dispersive spectrometry. From results of controlled precipitation experiments of cerium and zinc salts performed in carbonated medium, the presence of cerium in the corrosionlayer and its protective character could be attributed to the formation of a mixed double lamellar zinc-cerium product. Therefore, addition to zinc of less than 2 wt.% of cerium or lanthanum allow to improve the corrosion resistance of zinc. However, by increasing the rare earth content in the alloys, the galvanic coupling phenomenon becomes more important and makes the alloys less resistant than pure zinc
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Azad, Ali Bawan, and Sara Ahmadiyan. "Livslängdsdimensionering av korrosionsutsatta betongkonstruktioner." Thesis, KTH, Byggteknik och design, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255606.
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Through history, iron has mainly been used as reinforcement in concrete. Contemporary building technology would not have been possible without reinforced concrete, however, from a global perspective, many concrete buildings have begun to encounter reinforcement corrosion, mainly due to chlorides and carbonation. When the chlorides come into contact with the reinforcing bars, a chemical reaction begins, which causes the iron to oxidize and begin to corrode. In a humid environment when the reinforcement corrodes, the iron expands and bursts the concrete from inside, which in turn results in cracks occurring in the concrete structure. In an environment with lack of oxygen, it often occurs that non expanding rust products form that are not defected on the concrete surface occurs through discoloring or spalling. This type of damage is not detected ocularly and therefore forms a more serious type of injury. This type of rust is a silent type of damage that can cause deteriorated bearing capacity in the construction, since the cross-sectional area of the reinforcement in the concrete decreases. Sweco has been involved in a couple of projects where there have been huge problems due to corrosion of reinforcement. The damages that emerged leading to the repairs of these type of damage costing large sums. This report is based on previous projects, articles, literature studies, reports and interviews. Interviews have been conducted with competent people who have shared their valuable opinions, knowledge and experiences. In order to stop ongoing corrosion of reinforcement and also repair the damage, several alternative solution and repair measures have been devolped. Some of the most relevant suggestions in this report is to remove the damaged concrete and then re-cast or alternatively cast in cathodic protection or a combination of these.Genom historien har man främst använt sig av järn som armering i betong. Samtidens byggteknik hade inte varit möjlig utan armerad betong, dock behöver man vara uppmärksam på armeringskorrosion framför allt på grund av klorider och karbonatisering. När kloriderna kommer i kontakt med armeringsjärnen påbörjas en kemisk reaktion som leder till att järnen oxiderar och börjar korrodera. I fuktig miljö när armeringen korroderar, expanderar järnen och spränger betongen inifrån vilket i sin tur resulterar i att sprickor uppstår i betongkonstruktionen. I syrefattiga miljöer uppstår det oftast svartrost som är den typ av skada som uppstår inuti en betongkonstruktion. Denna typ av skada upptäcks inte okulärt och blir därför en allvarligare typ av skada. Svartrost är även den typ av skada som kan förorsaka försämrad bärighet i konstruktionen eftersom tvärsnittsarean hos armeringen i betongen minskar. Sweco har varit inblandade i ett par projekt där det har förekommit enorma problem på grund av armeringskorrosion. Skadorna som har uppstått på grund av armeringskorrosion har lett till att reparationerna av dessa skador har varit kostsamma. Denna rapport är baserad på tidigare projekt, artiklar, litteraturstudier, rapporter samt intervjuer. Intervjuer har genomförts med kompetenta personer som har delat med sig av sina värdefulla åsikter, kunskaper och erfarenheter för att få en bättre uppfattning av konsekvenserna som uppstår på grund av armeringskorrosion. För att stoppa pågående armeringskorrosion och även reparera skadorna, har reparationsåtgärder i denna rapport tagits fram. Några utav de mest relevanta förslag på åtgärder i denna rapport är att ta bort den skadade betongen för att sedan gjuta på nytt, alternativt gjuta in katodiskt skydd eller en kombination av dessa.
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Tomek, Jan. "Povrchová úprava kontejneru CASTOR." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230829.
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Master’s thesis deals with the problems of the inner surface finish design for the CASTOR container. In the theoretical part are analyzed properties of metallic surfaces with their defects and various options of surface finishes for increased protection. The practical part of the thesis is focused on the design of appropriate technologies for specific requirements of the surface finish for the CASTOR container, creating test samples and their evaluation.
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Axelsson, Erik, and Mårten Ringborg. "Katodiskt Korrosionsskydd : Hur fungerar katodiskt korrosionsskydd ombord på fartyg?" Thesis, University of Kalmar, Kalmar Maritime Academy, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hik:diva-1703.
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Idén till detta arbete uppstod som en följd av att vi på den fartygsförlagda praktiken upptäckt att kunskapen om katodiskt korrosionsskydd är mycket bristfällig hos många ombordanställda. Vi har även gjort en mindre undersökning bland yrkesverksamma maskinister för att se hur kunskapsnivån inom detta område ligger ombord. Undersökningen visar att vår hypotes om kunskapsnivån stämde till stor del. Ytterliggare ett skäl till att vi studerat det här området är att vi själva har velat fördjupa oss i ämnet, då våra egna erfarenheter endast varit att skriva av siffror från en display. Vår huvudfrågeställning har varit, Hur fungerar katodiskt korrosionsskydd ombord på fartyg? För att få svar på denna frågeställning har vi bedrivit litteraturstudier inom ämnet. De teoretiska kunskaperna har vi samlat från internet och böcker. De praktiska kunskaperna har vi fått från tidigare praktikperioder samt under praktik på MS Silja Galaxy under perioden december 2008 till januari 2009.
The idea for this exam paper arose under our onboard training periods. Under these periods we understood that the knowledge in cathodic corrosion protection was poor among the engine personal. We have also made a minor survey among marine engineers to see how the knowledge in this area is onboard. The survey shows that our hypothesis on the level of knowledge corresponded to a large extent. Further reason why we studied this area is that we wanted to deepen us in this subject, when our own experience only was to write numbers from a display. Our main question has been how cathodic corrosion protection work at ships. In order to answer this question, we conducted literature studies in the subject. The theoretical knowledge we have gathered from internet and books. The practical knowledge we have gained from previous training periods and during onboard training on MS Silja Galaxy in December 2008 to January 2009.
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Zanibellato, Alaric. "Synthèse et études physico-chimiques d’un agglomérat calcomagnésien formé sur acier en milieu marin : un éco-matériau pour la protection du littoral." Thesis, La Rochelle, 2016. http://www.theses.fr/2016LAROS005/document.
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Un nouveau procédé, basé sur une adaptation innovante du principe de protection cathodique des ouvrages métalliques en milieu marin, consiste à favoriser la précipitation d’un agglomérat calcomagnésien sur plusieurs centimètres d’épaisseur. En présence de sable et de coquillages, cet agglomérat pourrait permettre de stabiliser des zones littorales en cours d’érosion ou d’améliorer l’ancrage d’enrochements brise-lames. L’objectif de ce travail est d’étudier et de comprendre les mécanismes réactionnels de formation de cet agglomérat permettant une précipitation en volume loin de la cathode afin d’en optimiser la vitesse de formation ainsi que ses propriétés mécaniques. Premièrement, il a été montré dans ces travaux que le milieu électrolytique pouvait influer sur la croissance du dépôt, avec une possible inhibition de formation de carbonate de calcium pour les faibles potentiels. L’influence des produits de corrosion dans le mécanisme de protection cathodique a également été mise en évidence grâce à des polarisations effectuées dans NaCl, eau de mer artificielle et naturelle. Deuxièmement, des essais d’un mois en courant imposé ont été menés du laboratoire jusqu’au site naturel, afin de se rapprocher des conditions réelles. La densité de courant appliquée ainsi que les conditions hydrodynamiques sont des facteurs clefs étroitement liés l’un à l’autre, influant sur la masse et le rapport Ca/Mg. Ces travaux ont aussi permis de mettre en avant l’influence du temps de polarisation sur la composition du dépôt calcomagnésien, présentant une cinétique de croissance stable mais une fluctuation de composition après 15, 30 et 60 jours. Cette variation interne du rapport Ca/Mg, attribuée à un processus de « dissolution/précipitation » dépendant du gradient de pH, ainsi que la répartition de ces éléments au sein du dépôt pourraient jouer un rôle majeur dans l’évolution de la tenue mécanique du dépôt au cours du tempsA new method, based on an innovative adaptation of cathodic protection principle of metal structures in marine environment, is to promote the precipitation of a calcareous agglomerate several centimeters thick. In the presence of sand and shells, this cluster could stabilize coastal areas being eroded or improve anchorage of breakwater riprap. The objective of this work is to study and understand the reaction mechanisms allowing to create a voluminous calcareous deposit away from the cathode and to optimize deposition time as well as its mechanical properties. First, it was shown in this work that the electrolytic medium could affect the growth of the deposit, with a possible inhibition of formation of calcium carbonate fot the low potential. The influence of corrosion products in the cathodic protection mechanism was also highlighted through polarizations performed in NaCl, artificial and natural sea water. Second, one month test with impressed current were conducted from laboratory to natural site, in order to get closer of real conditions. Current density and hydrodynamic conditions are key factors closely bonded to each other, affecting the mass and composition of the Ca/Mg ratio. This work has also helped to highlight the influence of the polarization time on the composition, with stable growth kinetics but a composition’s evolution after 15, 30 and 60 days. This internal variation of the Ca/Mg ratio attributed to a process of « dissolution/precipitation » is pH dependent and the distribution of these elements within the deposit could play a major role in the evolution of the mechanical strength of deposit over time
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Maya, Visuet Enrique. "Electrolyte Transport And Interfacial Initiation Mechanisms Of Zinc Rich Epoxy Nanocoating/Substrate System Under Corrosive Environment." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1430762942.
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Xavier, Marco Antonio Kresko. "Revestimentos de polianilina e polianilina/melamina sobre aço inox 304: eletrossíntese em meio aquoso neutro e avaliação da proteção contra corrosão em meio NaCl 0,5 mol/l." Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/876.
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A polianilina é dos polímeros condutores mais estudados e com diversas aplicações, dentre elas o uso no recobrimento de aços para proteção à corrosão. Este trabalho objetivou encontrar as condições de eletrossíntese de polianilinas em meio aquoso neutro e a avaliação de proteção à corrosão, tendo como substrato o aço inox 304. As polianilinas eletrossintetizadas foram uma forma pura (PAni) e outra modificada com a adição de melamina (PAni/MM). Dentre as justificativas deste trabalho está a necessidade de aprofundar os escassos estudos em eletrossínteses em meio aquoso neutro. Neste trabalho, são apresentados as condições de eletrossíntese das polianilinas, a caracterização preliminar das polianilinas por UV-visível, FTIR e MEV, ensaios de polarização potenciodinâmica e impedância eletroquímica do aço inox 304 sem e com filmes das polianilinas para avaliar a resistência à corrosão em meio aquoso de NaCl 0,5 mol/L. O trabalho mostrou que a eletrossíntese das polianilinas em meio aquoso neutro é viável. Além disso, foi verificada a seguinte ordem do potencial de corrosão, do menor para o maior: aço inox 304 puro, aço inox 304 com PAni e aço inox 304 com PAni/MM.Polyaniline is one of the most studied conducting polymers and with various applications, including use on steels for corrosion protection. This work aimed to find the conditions for electrosynthesis of polyanilines in neutral aqueous media and to evaluated the corrosion protection of 304 stainless steel. The electrosynthesizeds polyanilines were one pure form (PAni) and one with the addition of melamine (PAni/MM). One of the justifications of this work is the need to deepen the scarce studies in electrosynthesis in neutral aqueous media. In this work, we will see the conditions for electrosynthesis of polyanilines, the UV-visible, FTIR and SEM polyanilines preliminary characterization, the potentiodynamic polarization experiments and impedance spectroscopy of 304 stainless steel without and with films from polyanilines for evaluate the corrosion resistance in NaCl 0,5 mol/L aqueous media. This work showed that electrosynthesis of polyanilines is feasible in neutral aqueous media. In addition, it was verified the following order of corrosion potencial, from lowest to highest: pure 304 stainless steel, 304 stainless steel with PAni and 304 stainless with PAni/MM.
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Sousa, Josà Arimateia Cavalcante de. "Cathodic protection semisubmersÃveis floating metal chambers for water catchment. Case Study: Weir GaviÃo." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11364.
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As part of the water resources policy of the state of CearÃ, in Northeast Brazil,
COGERH, as an operational instrument, has among its tasks the distribution of bulk water for
various uses. Among the water systems that COGERH operates are the pumping stations,
which are responsible for supplying water for cities, industries, irrigation, etc. It is vital that
these structures operate satisfactorily and efficiently. Among the many devices that make up
the pumping stations are the semisubmersible floating metal chambers that are located on the
water surface of the reservoirs, providing support to the pumps and motors such that they can
be set and operated reliably and efficiently. However, these structures are made from steel and
therefore are subject to severe corrosion processes, making it necessary for the painting of the submerged areas to ensure the necessary protection to avoid oxidation of them. As painting alone is not a process that ensures 100% efficiency in terms of coating and has a relatively short lifespan, complementary processes are necessary to ensure safe protection against corrosion. Among these processes is the Cathodic Protection, which ensures that, while a difference in electrochemical potential is being generated between the structure to be protected and a sacrificial anode, the structure will not undergo corrosion processes. For this study, it has been designed and installed an Impressed Current Cathodic Protection System with a potential ON of protection of -2.67 Volts (DC) for the Pumping Station known as "EB GaviÃoâ chosen due to its strategic importance within the state infrastructure of water resources, responsible for supplying water for major cities and industries.
Keywords :Dentro da polÃtica dos recursos hÃdricos do estado do CearÃ, no Nordeste do Brasil, a COGERH, como instrumento operacional, tem entre suas atribuiÃÃes a distribuiÃÃo de Ãgua bruta para usos diversos. Dentre os sistemas que a COGERH operacionaliza estÃo as estaÃÃes de bombeamento, as quais sÃo responsÃveis por abastecer cidades, indÃstrias, irrigantes, etc. à fundamental que tais estruturas operem de forma satisfatÃria e eficiente. Dentre os muitos equipamentos que compÃem as estaÃÃes de bombeamento estÃo Ãs cÃmaras metÃlicas flutuantes emisubmersÃveis que se localizam na superfÃcie de Ãgua dos reservatÃrios, dando sustentaÃÃo para que as bombas e motores possam ser fixados e operados de forma confiÃvel e eficiente. No entanto estas estruturas, por serem de aÃo, estÃo sujeitas a processos de corrosÃo severos, fazendo-se necessÃrio que a pintura das Ãreas submersas assegurem a proteÃÃo necessÃria para que nÃo haja oxidaÃÃo das mesmas. Como a pintura nÃo à um processo que garante uma eficiÃncia de 100% e termos de revestimento e tem uma vida Ãtil relativamente curta, fazem-se necessÃrios processos complementares para uma segura proteÃÃo anti-corrosÃo. Dentre esses processos està a ProteÃÃo CatÃdica que assegura que enquanto estiver sendo gerada uma âdiferenÃa de potencial eletroquÃmicoâ entre a estrutura a ser protegida e um anodo de sacrifÃcio a estrutura nÃo sofrerà severos processos de corrosÃo. Neste estudo foi dimensionado e instalado um Sistema de ProteÃÃo CatÃdica por Corrente Impressa assegurando um potencial ON de proteÃÃo de -2,67 Vcc para a estaÃÃo de bombeamento denominada âEB GaviÃoâ pela importÃncia estratÃgica que ocupa dentro da infraestrutura estadual de recursos hÃdricos, fazendo parte de sistema responsÃvel pelo abastecimento de importantes cidades e indÃstrias.
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Cé, Nataly Araújo. "Measuring the effect of cathodic protection on the performance of thermally sprayed aluminium coatings at elevated temperature." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/173316.
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Alumínio Pulverizado Termicamente (TSA) é amplamente utilizado em instalações offshore como revestimento de ânodo de sacrifício em tubulações de aço carbono. O transporte e a instalação desses componentes podem levar a pequenos danos no revestimento, o que pode expor a superfície do aço à água do mar. Sabe-se que o depósito calcário é formado na superfície do aço polarizado catodicamente. Assim, esta pesquisa avaliou o TSA aplicado por sistema de pulverização de arco duplo (TWAS) no aço ao carbono S355J2 + N quando ocorrem danos (holidays) para estudar a formação de depósitos calcários no aço e adquirir dados sobre o desempenho do TSA sob altas temperaturas. A aplicação de diferentes condições também foi considerada: presença de selantes; liga do revestimento (99,5% de Al e Al-5% de Mg) e condições enterradas/não enterradas. Dois tipos de experimentos foram realizados: i) testes em potencial livre sob temperaturas constantes (30, 60 e 90°C) e diferentes tamanhos de holidays (expondo 5, 10 e 20% da superfície do aço) e ii) testes sob gradient térmico onde óleo a ~125°C foi adicionado em uma torre polimérica e água externa a ~10°C ficou em contato com a superfície das amostras (tanto potencial livre como polarização de -950 mVAg/AgCl foram aplicados). Análises incluíram inspeção visual, microscópio eletrônico de varredura e difração de Raio-X. A partir dos testes em temperaturas constante, o TSA atingiu um bom potencial de proteção (-800 a -900 mVAg/AgCl) e pouca diferença nos resultados devido à diferença na composição doTSA e no tamanho do holiday foi observada. As taxas de corrosão foram mantidas entre 0,02 e 0,01 mm/ano. No ensaio sob gradiente térmico e potencial livre, a perda de revestimento e as taxas de corrosão foram de 0,4 a 0,002 mm/ano. Além disso, o potencial alcançado foi de uma faixa menor do que a obtida anteriormente (-745 a -835 mVAg/AgCl). No entanto, quando o TSA foi combinado com proteção catódica externa e gradiente térmico, a espessura do TSA foi satisfatório e as taxas de corrosão obtidas foram inferiores a 0,076 mm/ano. O depósito calcário formado no holiday protegeu o aço contra a corrosão e seu mecanismo de crescimento baseado nesta pesquisa foi construído.Thermally Sprayed Aluminium (TSA) is widely used in offshore facilities as sacrificial anode coating for carbon-steel risers and pipelines. Transportation and installation of those components can lead to small damages in the coating, which can expose the steel surface to the seawater. It is known that calcareous deposit is formed on the cathodically polarised steel surface. Thus, this research evaluated the TSA applied by twin wire arc spray system (TWAS) on S355J2+N carbon-steel when damage (holidays) is present in order to study the calcareous deposit formation on steel and acquire data regarding the TSA performance at high temperatures. Application of different conditions was also considered: presence of sealing; coating alloy (99.5%Al and Al-5%Mg) and buried/unburied conditions. Generally, two types of experiment were conducted – i) tests at free potential at steady temperatures (30, 60 and 90°C) and different holiday sizes (exposing 5, 10 and 20% of the steel surface) and ii) tests under thermal gradient where oil at ~125°C was added in polymeric tower and external water at ~10°C was in contact with the samples surface (both free potential and polarisation of -950 mVAg/AgCl were applied). Methodology of analyses included visual inspection, scanning electron microscope and X-ray Diffraction. From the tests at steady temperatures, the TSA reached a very good protective potential (-800 to -900 mVAg/AgCl) and little difference in results due to difference in TSA composition and holiday size was observed. Corrosion rates were kept between 0.02 and 0.01 mm/year. From the thermal gradient test under free potential, the coating loss and corrosion rates were 0.4 to 0.002 mm/year. Also, the potential achieved was in a lower range than previously obtained (-745 to -835 mVAg/AgCl). However, when TSA was combined with external cathodic protection and thermal gradient, the thickness of the TSA was satisfactory and corrosion rates obtained were below 0.076 mm/year. The calcareous deposit formed within the holiday protected the steel substrate against corrosion and its growth mechanism based in this research was built.
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Danovič, Jakub. "Eliminace degradačních procesů kovových tenkých vrstev." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-221002.
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This work deals with issues of thin films, their behaviour in different enviroments and protection of theese films against unwanted degradation processes. Metal thin films are made by special physical or chemical methods in the presence of vacuum. Deposition is performed on properly cleaned substrate made of different materials, for example glass, ceramics or another metal. Theese films degrades under the influence of moisture, heat and other. There are several types of films on different bases made to prevent thin films against degradation.
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Yang, Wen-Chih, and 楊文治. "Study on AC Stray Currents Corrosion under Cathodic Protection Function." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/81679669964863275184.
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碩士國立臺灣科技大學
機械工程系
93
Influence of AC induced voltages upon cathodic protected low carbon steel has been studied experimentally. The applied DC cathodic potential is -1.0 V (vs. SCE), while the AC induced voltages range from 1.0 V to 4.0 V. It is found that the trend of AC corrosion increases with increasing AC induced voltages. In other words, corrosion rate increases with increasing AC current densities. Pitting corrosion is apparent when AC current densities are larger than 100 A/m2. Metal shinning occurs on the pit’s surface and the dimensions of pits increase with increasing AC induced voltages. By conducting various laboratory tests, AC currents may pose a threat to low carbon steel and cathodic protection (CP) requirements needed to mitigate the possible adverse AC current effects. However, even though CP criteria (-850 mV vs. Cu/CuSO4) are matched, AC corrosion still takes place as AC currents are larger than 100 A/m2.
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Abooameri, Farid. "Evaluation of cathodic protection in reinforced concrete bridges." Thesis, 1994. http://hdl.handle.net/1957/35182.
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Steel corrosion in reinforced concrete is a major concern to
transportation agencies nationwide because of the expenses incurred for
repair and ultimate shortening of bridge life. Cathodic protection (CP), as a
remedy, has been applied to reinforced bridges in the US since 1974.
However, application of this technique is largely empirical, lacking
fundamental understanding. In order to optimize the performance of a CP
system, it is important to monitor the rebar potential with respect to a reliable
reference electrode. Moreover, because of potential variation in the concrete,
reference cell placement is fundamental to ensure effective protection.
The work plan was divided into two parts: laboratory scale
experimentation and computer simulation. In the experimentation section,
the response of graphite probes was compared to that of an Orion silver-silver
chloride electrode. Graphite probes behaved as well as the standard electrode.
Furthermore, the home-made graphite probes behaved the same as the
commercial ones. This will allow much greater experimental latitude since
the home-made probes are much more economical than the commercial
ones.
A finite difference code was developed to assess the performance of
cathodic protection. The potential distribution in a two dimensional
geometry of a concrete block with a sprayed zinc anode at one boundary and
an iron cathode at the other side was calculated under cathodic protection.
The equations were solved by means of a Gauss-Seidel iterative method with
the help of an overrelaxation factor. An interval halving method was used to
solve for nonlinear boundary condition at the iron.
The effects of concrete pore saturation, concrete cover, and applied potential were studied to determine the degree of protection and proper placement of the reference electrode in concrete. Furthermore, a sensitivity analysis was performed versus input parameters: concrete conductivity, oxygen mass transfer coefficient, and oxygen reduction polarization parameters. The results of the simulation showed that the center of the rebar is less protected than the other locations. Therefore, the reference electrode should be located as close to the center as possible.Graduation date: 1995
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林景崎. "On the corrosion prevention of steel by cathodic protection and inhibitors in marine environment." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/04804585814639603904.
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Don, Tseng Ming, and 曾銘棟. "On the corrosion and cathodic protections of pipelines and tubes in the specific environment." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/74458536991671694371.
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博士國立清華大學
材料科學(工程)研究所
81
The potential decay from the anode bed along the pipeline can be predicted from formula reported elsewhere for conventional shallow groundbed system (surface type remote groundbed), but in the deepwell groundbed system, few data are available. The resistance of the entire cathodic protection current circuit is discussed theoretically and the potential change for the deep well groundbed system of the applied current cathodic protection method along the pipeline for the anode in different soil depths of soil are also derived from the field tests. Equations for the calculation of the resistance of the conventional surface- type ground bed with single anode and multi-anodes have been discussed in many papers. For deep well ground bed system, the resistance of a single vertical anode can be calculated by using the Dwight equation[1]. But this is not applicable to all cases, especially to the old system of deep well groundbed. In this paper data from field test were presented, also a novel equation was introduced and proved to be effective in the calculation of the deep well ground bed resistance. In this study the cause that leads to the damage of the condenser tube made of copper-nickel alloy is analyzed. The corrosion behavior and the possible ways of corrosion prevention of copper-nickel alloy in sulfur- contaminated seawater is discussed.
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Ronge, Emanuel. "In-Situ Environmental TEM Studies of Electro- and Photo-Electrochemical Systems for Water Splitting." Doctoral thesis, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-157D-8.
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