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1
Brokbartold, Marcel [Verfasser], Bernd [Gutachter] Marschner, Marianne [Gutachter] Grupe, and Hermann [Gutachter] Gies. "Characteristics and environmental relevance of Pb derived from red lead anti-corrosion paint in soils and soil-plant systems / Marcel Brokbartold ; Gutachter: Bernd Marschner, Marianne Grupe, Hermann Gies ; Fakultät für Geowissenschaften." Bochum : Ruhr-Universität Bochum, 2012. http://d-nb.info/1202605249/34.
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Li, Kwan (Kwan Hon). "Microbially influenced corrosion in sour environments." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/88382.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-123).
Microbially influenced corrosion (MIC) is a costly and poorly understood source of corrosion that plagues many modern industrial processes such as oil extraction and transportation. Throughout the years, many possible mechanisms for MIC have been proposed. One specific proposed mechanism was tested in this thesis: that the metal-binding characteristic of bacterial biofilms enhanced corrosion when it appears in conjunction with an iron sulfide film. Two model biogels were used: calcium alginate, which has this metal-binding property, and agarose, which does not. In pursuit of this hypothesis, iron sulfide films were grown on mild steel coupons. Two distinct forms of iron sulfides were grown: a loose black product at low sulfide concentrations, and an adherent gold product at high sulfide concentrations. Many materials characterization techniques were attempted, and the black corrosion product was found to be a mixture of greigite and marcasite. However, this composition was observed to change irreversibly with the application of a laser that caused the material to either heat and/or dry. The resulting golden-colored corrosion product was found to consist mainly of monosulfides, implying the presence of mackinawite or pyrrhotite. By using electrochemical polarization experiments, it was found that calcium alginate enhanced the rate of corrosion; agarose reduced the rate of corrosion. This is in contrast to previously published literature. Contrary to the initial hypothesis, adding an underlying iron sulfide film did not appreciably alter the measured rate of corrosion. Additionally, it was found that biofilms generated by sulfate-reducing bacteria (SRB) enhanced corrosion in a manner similar to the calcium alginate gel, and lysing the cells within the biofilm did nothing to alter this effect. This implies that the biofilm itself, even in the absence of active bacterial metabolic activity, can enhance corrosion rates observed in MIC.
by Kwan Li.
S.M.
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Been, Jantje. "Titanium corrosion in alkaline hydrogen peroxide environments." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/NQ34511.pdf.
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Neseyif, S. "Predicting corrosion rates within coal gasification environments." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309623.
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Tunnicliffe, Matthew. "Corrosion of lead anodes in metallic electrowinning environments." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/37789.
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The corrosion of anodes in electrowinning is costly because of their relatively short lifespan, material cost, and their impact on cathodic deposit quality. The objective of this thesis was to understand the corrosion behavior of Pb anodes in electrolyte simulating Zn and Ni electrowinning conditions. Pb-based alloys have been used because they are cheap, conductive and stable at high potential and low pH. Experiments in this thesis included open circuit potential (OCP), potentiodynamic, and potentiostatic polarizations. The parameters studied include; icorr, Ecorr, slope of the oxygen evolution region and O₂ potential.
For Zn electrowinning, variables changes included modifying H₂SO₄, Mn²⁺, Cl⁻, Zn²⁺ concentrations and increasing temperature. The best corrosion resistance in Zn electrowinning was achieved by increasing H₂SO₄ concentration, using 15 g/L Mn²⁺, 0 g/L Cl⁻, and increasing both Zn²⁺ temperature. Corrosion products were studied using SEM and EDX and the relationship between surface morphology of the working electrode and operating potential. Deaerating the cell reduced the dissolved oxygen in the cell and generally increased icorr, oxygen evolution region slope and OER overpotential. For Ni electrowinning applications, three materials were used as cast PbAg, rolled PbAg, and as cast PbCaSn. The effects of H₂SO₄ and Cl- on corrosion behavior were studied using both potentiodynamic and galvanostatic polarizations. Corrosion rates were determined by measuring the length of the discharge peak after 24 hours galvanostatic polarization and SEM and XRD were used to determine the surface morphology and phase composition of the anodes.
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Glanvill, Sarah Jane Marie. "Atmospheric corrosion of AA2024 in ocean water environments." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8554/.
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Observations of atmospheric corrosion on aluminium alloy AA2024-T3 were made within droplets of NaCl solution and simulated ASTM ocean water. High speed in-situ synchrotron X-ray tomography has been used to observe the initiation and propagation of corrosion sites. Tomographic scans had a temporal resolution of 300s per full tomographic scan, providing a non-destructive visualisation of corrosion. Sites initiate at numerous surface morphologies, including at intermetallic inclusions, under surface deposits and salt crystals, and also at sites with no obvious micron-scale microstructural features. It was observed that corrosion sites grow discontinuously and inhomogeneously when conditions are constant, consistent with bursts of dissolution followed by some repassivation. The nature of corrosion products was investigated with Raman spectroscopy and EDX. The dominant corrosion product was Dawsonite for both droplet solutions, however the distribution of corrosion products differed between the two types of droplet. NaCl droplets spread more, resulting in fewer, larger corrosion sites. ASTM ocean water droplets showed multiple small corrosion sites within the droplet owing to the presence of Hydrotalcite around the droplet perimeter. Corrosion development under wet-dry cycling conditions was different for NaCl and ASTM ocean water droplets. Under NaCl droplets, no growth or initiation was observed during “dry” phases. However, ASTM ocean water remains partially wet in “dry” periods as some of the salt constituents in ASTM ocean water remain hydrated. As a consequence, corrosion site growth is able to continue.
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Gao, Xin. "Localized Corrosion Initiation of Steel in CO2 Environments." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1596657895973621.
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Harty, Brian Dudley. "Corrosion fatigue of engineering alloys in aqueous environments." Doctoral thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/18215.
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A comparative study of the fatigue crack growth rate (FCGR) behaviour of five alloys in air and in aqueous environments has been performed. The alloys tested include: mild steel as a reference material, a corrosion resistant dual phase steel, 3CR12, a proprietary martensitic stainless steel, AISI 431, a newly developed 8% Cr martensitic steel, Alloy 825, and a newly developed corrosion-abrasion resistant metastable austenitic alloy, 1210. Tests were conducted in laboratory air, distilled water at rest potential, 500 ppm chloride solution at rest potential, 1000 ppm chloride solution at rest potential, and 1000 ppm chloride solution at -1200 m V see; solution temperatures were maintained at 25⁰ C. Crack growth rate tests were performed using sinusoidal loading at a load ratio R = 0.1, a frequency of 3Hz in the laboratory air, and a frequency of 1 Hz in the aqueous environments. At the completion of testing, fracture surfaces were studied using a scanning electron microscope. In air, the mild steel and 3CR12 display comparable rates of cracking and exhibit a greater resistance to fatigue crack propagation than the martensitic AISI 431 and Alloy 825; Alloy 825 shows the least resistance to fatigue crack propagation. The deformation induced transformation in 1210 gives this alloy the greatest resistance to fatigue crack propagation in air. Fatigue crack growth rates were all enhanced in the aqueous environments. The greatest overall rate of environmentally assisted cracking was shown by alloy 825 while the lowest was shown by the mild steel. Although the rate of cracking of 1210 in the aqueous environments was less than that of Alloy 825, 1210 was influenced the most by the aqueous environments. An environmentally assisted cracking index shows that the rate of fatigue crack propagation in 1210 is increased by 32 times in the 500 ppm chloride solution at low stress intensities. The fatigue crack growth rates of mild steel and AISI 431 were significantly influenced by the cathodically polarised conditions in the 1000 ppm chloride solution, compared to the rest potential conditions. In these cases hydrogen was seen to be evolved from the specimen surfaces. Changes in the fatigue crack growth rate behaviour were accompanied by changes in the fracture surface morphologies. The observed changes varied for each alloy and for each environment, and were manifest by the degree of intergranular cracking, cleavage, quasi cleavage, and increased coarseness of the transgranular cracking. The fracture surface morphologies are reported and discussed in detail. In general, the fracture surface morphologies could be directly related to the relative degrees of environmental influence on the rate of cracking; results are explained in terms of existing hypotheses. It is suggested that the environmentally assisted cracking of mild steel and AISI 431 at cathodic potentials in the 1000 ppm chloride solution could only be attributed to hydrogen assisted cracking. Similarly, it is suggested that the large crack growth rate acceleration of 1210 in the aqueous environments could also be attributed to hydrogen. The similar fracture surface morphologies observed on the other specimens after tests in the aqueous environments suggests-that hydrogen could be responsible for the environmentally assisted cracking of all the steels in aqueous environments.
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Morales, Gil Perla. "Exploring corrosion inhibition in acidic and oilfield environments." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/exploring-corrosion-inhibition-in-acidic-and-oilfield-environments(a08cd84c-fa3a-4378-88dc-f467ac4f8f56).html.
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The goal of this thesis is to probe the functionality of 2-mercaptobenzimidazole (MBI) as corrosion inhibitor of carbon-steel in both strong and weak aqueous acidic solutions (HCl and H2CO3). To achieve this target electrochemical techniques have been employed, in combination with substrate analysis. Concerning aqueous HCl media, results demonstrate that MBI is an effective corrosion inhibitor, functioning essentially equally well in 1 M, 0.1 M, and 0.01 M HCl concentrations. X-ray photoelectron spectra suggest that MBI is typically bound to the surface in two tautomeric forms (thione and thiol). Furthermore, these data indicate that substrate termination varies as a function of both HCl and MBI concentration, with the interface consisting of MBI bound to film-free carbon-steel on highly inhibited substrates. In further work, the impact of dissolved oxygen, solution temperature, and immersion time on MBI performance in HCl solutions has been assessed. The latter two parameters have considerable influence on MBI inhibition efficiency. More specifically, it was found that MBI decreases dramatically its inhibition efficiency between 60°C and 70°C in 1 M HCl, and also apparently work less well as substrate immersion time increases. As regards MBI performance in deaerated CO2-saturated NaCl (0.62 M) solution, results demonstrate that MBI effectively inhibits corrosion within the parameter space explored i.e. solution temperatures of 30°C and 55°C and total applied pressures (p(H2O) + p(CO2)) of 1 bar and 20 bar. The performance of MBI does not vary greatly for different combinations of these temperatures and pressures. Post immersion substrate characterisation with XRD and SEM indicate that no significant surface scaling occurs under these conditions.
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Sutton, Jeremy. "Microbially influenced corrosion (MIC) of steels in mono- and hyper-baric environments." Thesis, Robert Gordon University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241029.
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Horspool, Dean. "Development of corrosion fatigue testing in sour oilfield environments." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5047/.
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The development of flexible pipelines and risers has been a key driver in allowing the oil and gas industry to develop fields in deeper and deeper waters, utilising floating production technologies. During service, the annulus environment located between the two polymer layers of the pipe may become corrosive. Permeation of corrosive species from the produced fluids along with permeation and subsequent condensation of water in the annulus of the pipe may result in the development of an acidic aqueous environment. If this situation occurs in service the integrity of the carbon steel tensile armour wires located in the annulus may be at risk. As such, it is the aim of the current research project to investigate the effect of simulated corrosive oilfield environments on the fatigue life of the tensile armour wire component of the pipe.
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Tzagkaroulakis, Ioannis. "Real time nanogravimetric monitoring of corrosion in radioactive environments." Thesis, Lancaster University, 2017. http://eprints.lancs.ac.uk/125116/.
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Monitoring and understanding the mechanism of metal corrosion throughout the nuclear fuel cycle play a key role in the safe asset management of facilities. They also provide information essential for making an informed choice regarding the selection of decontamination methods for steel plant and equipment scheduled for decommissioning. Recent advances in Quartz Crystal Nanobalance (QCN) technology offer the means of monitoring corrosion in-situ, in radiologically harsh environments, in real time and with high sensitivity. Oxalic acid has been widely used in nuclear plants and installations as a corrosion inhibitor for carbon steels and as a decontamination cleaning agent due to its ability to remove rust from the surface of ferritic metals and alloys. As an exemplar system for decontamination, the corrosion behaviour of mild carbon steel and pure iron samples in 1 wt% to 8wt% oxalic acid solutions have been measured and compared in real time and in situ using QCN. Corrosion rates measured using QCN are found to agree with those obtained using corrosion current (iCORR) measurements, with the added advantages of: (i) real time measurements of higher sensitivity with the potential for making them in situ; (ii) reduced uncertainty in the conversion of the QCN measured frequency change to a mass change-based corrosion rate compared to the conversion of the iCORR measured by LSV with Tafel extrapolation to mass change; (iii) the provision of mechanistic insights into the action of oxalic acid on Fe-rich steels. QCN has been used as a corrosion monitoring technique to study the impact of radiolytically generated peroxide on the corrosion protection afforded by oxalate to Fe surfaces. Results reveal that QCN can be the ideal means of measuring corrosion rates in situ, in real time, when two chemical reactions are taking place such as the ferrous oxalate layer production and the breakdown of the layer due to Fenton reactions. QCN has been studied as a corrosion monitoring technique for other decontamination solutions such as basic and acid permanganate and oxalic acid / nitric acid mixtures. Results reveal that QCN is a very promising tool for studying the efficacy of these new decontamination agent formulations with the sensor providing useful mechanistic information of the mode-of-action of the decontaminating agent from the mass change (gain or loss) in real time.
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Vaca-Cortés, Enrique. "Corrosion performance of epoxy-coated reinforcement in aggressive environments /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Banos, Antonios Konstantinos. "Investigation of uranium corrosion in mixed water-hydrogen environments." Thesis, University of Bristol, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.738234.
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Aribo, Sunday. "Corrosion and erosion-corrosion behaviour of lean duplex stainless steels in marine and oilfield environments." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7170/.
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Lean duplex stainless steels are becoming attractive for applications in oilfield and marine environments due to their economic advantages, very good mechanical properties and relatively good corrosion resistance. One such application is in the production of the carcass of flexible pipes. However, materials selection for such oilfield applications becomes more complex as a result of the interactions between corrosion and erosion. Much effort has been directed towards the study of erosion-corrosion behaviour of carbon steels and other passive alloys. However, the subject of erosion-corrosion of lean duplex stainless steels is still rarely reported. Moreover, data available in the literature on the localized corrosion resistance of the lean duplex stainless steels are limited to alkaline environments. Efforts have been made in this thesis to add to the existing data and to the understanding of the subject of localized corrosion and erosion-corrosion resistance of lean duplex stainless steels UNS S32101, UNS S32304 and UNS S82441 in oilfield environments. The lean duplex alloy UNS S32101 has been studied in detail because of its combination of high strength and good corrosion resistance. This research also compared the corrosion and erosion-corrosion resistance of lean duplex stainless steels with standard austenitic stainless steels UNS S30403 and UNS S31603 as well as duplex stainless steel alloy UNS S32205. Aerated 3.5% NaCl and synthesized CO2-saturated oilfield brines were considered as the corrosion media. Extreme erosion-corrosion conditions were simulated to design for severe environments often encountered in sand-containing oilfield pipeline systems. Breakdown potentials, under static conditions, were found to be more positive in the aerated 3.5% NaCl than the CO2-saturated oilfield brine solution. Also, lean duplex stainless steels and standard austenitic stainless steels exhibited similar resistance in both environments. X-ray Photoelectron Spectroscopy (XPS) analysis of the passive film indicated higher chloride incorporation in the CO2-saturated oilfield brine. This, in addition to lower pH of the CO2-saturated oilfield brine appeared to be the reason why the breakdown potential was more negative in this environment. Erosion-corrosion results showed that lean duplex stainless steels, UNS S32101 and UNS S32304, have higher resistance to pure-erosion damage than UNS S30403 and UNS S32205; better erosion-corrosion resistance than UNS S30403 austenitic stainless steel; and equivalent erosion-corrosion resistance to UNS S32205 standard duplex stainless steel. There was also a correlation between the erosion-corrosion resistance of the alloys and the sub-surface crystallography, microstructure and phase transformation. This, together with repassivation kinetics of the passive film, may be used to explain the erosion-corrosion behaviour of UNS S32101 and UNS S30403 in the oilfield slurry.
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Van, der Helm Mark Johan 1972. "Power plant degradation : a modular secondary plant and integral flow accelerated corrosion model." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8867.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, February 2001.Includes bibliographical references (leaves 198-204).
Flow Accelerated Corrosion (FAC) is the most prevalent material degradation mechanism for low carbon steel in steam-water flow systems. The band of uncertainty in predictions of wear rate due to FAC spans one to two orders of magnitude. Such a wide range of uncertainty inhibits the ability to devise safe and economical repair and replacement schedules. The goal of this thesis is to reduce uncertainty of predictions of wear caused by FAC. Reduction in the uncertainty in FAC wear rate predictions is achieved through the development of a new predictive FAC model, the incorporation of this model in a flow system analysis environment, and the use of this environment to identify improved methodologies for predicting FAC wear rate. The new FAC model is based on a published empirical model, published data, and physical mechanisms identified to be significant in the wear process. The new FAC model is shown to have less uncertainty for single phase lab data and single and two phase plant data. The flow system analysis environment is an interactive program that calculates parameters relevant to the FAC phenomenon based on plant description. Functionality of this environment is validated for each of the four calculations it performs: thermodynamic, thermal hydraulic, chemistry, and degradation rate. Additionally, this environment can be used to analyze contributions to uncertainty that are not yet identified. This environment was used to analyze the contribution to uncertainty from the current method of incorporating chemistry parameters in predictions of FAC wear. Based on this analysis, suggestions are made to improve these methods, thereby reducing prediction uncertainty and improving the knowledge necessary for safer and more economical plant operation.
by Mark Johan van der Helm.
Ph.D.
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Sundaram, S. K. "Corrosion and electrochemical protection of molybdenum and molybdenum disilicide in molten silicate glass environments." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/18906.
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Doja, Somi. "Corrosion behaviour of AZ31 magnesium alloy in highly alkaline environments." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61481.
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Magnesium (Mg) and its alloys are known for their high chemical reactivity. This property often poses issues related to undesirable corrosion, or degradation of exposed surfaces. The chemical reactivity of Mg can be also exploited, and as a result Mg alloys often find use as anode materials for fuel cells. However, due to a long term immersion of the anodes in highly alkaline environments, the problem of corrosion remains and needs to be evaluated. Therefore, in this research, the corrosion behavior of a commercially available magnesium alloy AZ31 in 45 wt% potassium hydroxide (KOH), a common electrolyte for alkaline fuel cells, was studied.
Immersion tests were performed for a total duration of 20 days to study the growth of corrosion products on the alloy’s surface. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) were carried out to characterize the structure and chemistry of the corrosion products. Also, electrochemical studies were carried out to study the kinetics of corrosion of the AZ31 alloy. Finally, the effect of adding 2 wt% sodium silicate (Na₂SiO₃) to the KOH electrolyte in order to manipulate the corrosion rate was also examined.
Tafel analysis confirmed that the corrosion potential of the AZ31 sample immersed in the Na₂SiO₃ + KOH solution reduced by 16% with respect to that of sample immersed in pure KOH. Although the AZ31 alloy contains only a trace amount of nickel, SEM-EDS characterization of the corrosion products revealed that they contained high levels of nickel, with XRD analysis confirming the presence of a nickel hydroxide layer. In the case of the sample immersed in Na₂SiO₃ + KOH electrolyte, an additional layer rich in silicates developed, and likely acted as a barrier for diffusion of ions from surface of the AZ31 sample to the electrolyte. EIS results of modeling the surface corrosion phenomena revealed that a modified Randle’s circuit represented the electrochemical processes occurring on the surface of the alloy. Warburg impedance for the sample immersed in Na₂SiO₃ + KOH was relatively high, suggesting a dissolution of ions from the surface into the highly alkaline KOH electrolyte.Graduate Studies, College of (Okanagan)
Graduate
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Sandberg, Jan. "Corrosion-induced release of zinc and copper in marine environments." Licentiate thesis, Stockholm : Division of corrosion science, Department of materials science end engineering, School of industrial engineering and management, Royal institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4051.
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Stone, Erica. "EFFECTS OF ORTHOPHOSPHATE CORROSION INHIBITOR IN BLENDED WATER QUALITY ENVIRONMENTS." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2961.
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This study evaluated the effects of orthophosphate (OP) inhibitor addition on iron, copper, and lead corrosion on coupons exposed to different blends of groundwater, surface water, and desalinated seawater. The effectiveness of OP inhibitor addition on iron, copper, and lead release was analyzed by statistical comparison between OP treated and untreated pilot distribution systems (PDS). Four different doses of OP inhibitor, ranging from zero (control) to 2 mg/L as P, were investigated and non-linear empirical models were developed to predict iron, copper, and lead release from the water quality and OP doses. Surface characterization evaluations were conducted using X-ray Photoelectron Spectroscopy (XPS) analyses for each iron, galvanized steel, copper, and lead/tin coupon tested. Also, a theoretical thermodynamic model was developed and used to validate the controlling solid phases determined by XPS. A comparison of the effects of phosphate-based corrosion inhibitor addition on iron, copper, and lead release from the PDSs exposed to the different blends was also conducted. Three phosphate-based corrosion inhibitors were employed; blended orthophosphate (BOP), orthophosphate (OP), and zinc orthophosphate (ZOP). Non-linear empirical models were developed to predict iron, copper, and lead release from each PDS treated with different doses of inhibitor ranging from zero (control) to 2 mg/L as P. The predictive models were developed using water quality parameters as well as the inhibitor dose. Using these empirical models, simulation of the water quality of different blends with varying alkalinity and pH were used to compare the inhibitors performance for remaining in compliance for iron, copper and lead release. OP inhibitor addition was found to offer limited improvement of iron release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increased total phosphorus, pH, and alkalinity reduced iron release while increased silica, chloride, sulfate, and temperature contributed to iron release. Thermodynamic modeling suggested that FePO4 is the controlling solid that forms on iron and galvanized steel surfaces, regardless of blend, when OP inhibitor is added for corrosion control. While FePO4 does not offer much control of the iron release from the cast iron surfaces, it does offer protection of the galvanized steel surfaces reducing zinc release. OP inhibitor addition was found to reduce copper release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increases in total phosphorus, silica, and pH reduced copper release while increased alkalinity and chloride contributed to copper release. Thermodynamic modeling suggested that Cu3(PO4)2•2H2O is the controlling solid that forms on copper surfaces, regardless of blend, when OP inhibitor is added for corrosion control. OP inhibitor addition was found to reduce lead release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increased total phosphorus and pH reduced lead release while increased alkalinity, chloride, and temperature contributed to lead release. Thermodynamic modeling suggested that hydroxypyromorphite is the controlling solid that forms on lead surfaces, regardless of blend, when OP inhibitor is added for corrosion control. The comparison of phosphate-based inhibitors found increasing pH to reduce iron, copper, and lead metal release, while increasing alkalinity was shown to reduce iron release but increase copper and lead release. The ZOP inhibitor was not predicted by the empirical models to perform as well as BOP and OP at the low dose of 0.5 mg/L as P for iron control, and the OP inhibitor was not predicted to perform as well as BOP and ZOP at the low dose of 0.5 mg/L as P for lead control. The three inhibitors evaluated performed similarly for copper control. Therefore, BOP inhibitor showed the lowest metal release at the low dose of 0.5 mg/L as P for control of iron, copper, and lead corrosion.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering PhD
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Carruth, Martin. "Corrosion of silicon based ceramics in simulated gas turbine environments." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248736.
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Sun, Dan. "Abrasion-corrosion of cast CoCrMo in simulated hip joint environments." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/67337/.
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Metal-on-metal (MoM) hip joint replacements have been increasingly used for younger and more active patients in recent years due to their improved wear performance compared to conventional metal-on-polymer bearings. MoM bearings operate at body temperature within a corrosive joint environment and therefore are inevitably being subjected to wear and corrosion as well as the combined action of tribo-corrosion. Issues such as metal sensitivity/metallosis associated with high levels of metal ion release triggered by the wear and corrosion products remain critical concerns. During the past few decades, significant research has been conducted into understanding the wear/lubrication mechanisms within the MoM hip joints in order to improve their performance and thereby prolonging their life. However, not much attention has been given to the combined effect of wear and corrosion of such devices in the hip joint environment, in addition, the role of third body particles and the effects of proteins have not been well understood. In this work, a systemic approach is presented for the first time for the mapping of abrasion and tribo-corrosion performance of a cast CoCrMo (F75) in simulated hip joint environments. The effects of third body particles have been studied in the MoM context using 4 μm SiC, 1 μm and 300 nm Al2O3, as well as sub-micron BaSO4. Modified tribo-testers (micro-abrasion, nanoindenter/scratching) incorporating a novel electrochemical cell have been used to monitor the abrasion-corrosion behaviour of the alloy in situ. The effects of solution chemistry, abrasives size / concentration and presence of proteins on the wear / corrosion level, wear-corrosion mechanisms, and the depassivation/repassivation kinetics of the CoCrMo have been explored. A variety of surface and sub-surface characterization techniques have been employed to identify the microstructual wear mechanism interactions. Results show that the change of protein concentration (0, 25% and 50% bovine serum) and pH (pH 7.4 and pH 4.0) of the test solutions can significantly influence the protein adsorption behaviour, which subsequently influence the wear rates (synergy), wear mechanisms as well as the wear-induced corrosion currents of the CoCrMo. For abrasion-corrosion tests, reducing abrasive size from 4 μm to 300 nm and/or abrasive volume concentration from 0.238 vol% to 0.006 vol% results in different abrasion-corrosion wear mechanisms (rolling or grooving abrasion) and the average wear-induced corrosion currents show a linear correlation with wear rates for 4 μm and 1 μm abrasives. For low volume concentration (< 0.03 vol%) slurries containing bovine serum, organo-metallic conglomerates have been found within the wear scars. These conglomerates help separate the surfaces, impose less damage to the surface passive film and polish the wear scars through a chemical mechanical polishing mechanism. In addition, tribo-corrosion tests at micro-/nano- scales reveal the effects of single abrasive particle on the surface/sub-surface microstructual change. This investigation has revealed the nanoscale wear mechanisms that generate nanoscale wear debris, the mechanical mixing of the surface nanostructure with adsorbed denatured protein and also the slip/dislocation systems that are present near and on abraded surfaces that are likely to disrupt the surface passive films. The findings give a better understanding of the evolution of the sub-surface nanocrystalline structures and tribo-layers formation seen for the retrieved implants. This near surface nanostructure layer and phase transformation might offer better wear resistance through these inherent self-protecting mechanisms (i.e. increased hardness); conversely, it may become the precursors to debris ejection and enhanced ion-release into the CoCrMo joints. This work established an experimental technique that gives greater understanding of the tribocorrosion behaviour of cast CoCrMo in simulated hip joint environments. In particular, the roles of third body abrasive particles and proteins have been addressed, which are relevant to clinical applications. The material multi-scale wear mechanisms as well as the evolution of the surface / subsurface microstructures and tribo-layers have been elucidated, which provide new insights into the in vivo wear mechanisms of CoCrMo. The findings of this study may provide some important indications for improved MoM joint materials, design, manufacture and evaluation.
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Fang, Haitao. "Investigation of Localized Corrosion of Carbon Steel in H2S Environments." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1323981659.
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Goodman, Lindsey R. "Stress corrosion cracking of X65 pipeline steel in fuel grade ethanol environments." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45790.
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In recent years, the demand for alternatives to fossil fuels has risen dramatically, and ethanol fuel has become an important liquid fuel alternative globally. The most efficient mode of transportation of petroleum-based fuel is via pipelines, and due to the 300% increase in ethanol use in the U.S. in the past decade, a similar method of conveyance must be adopted for ethanol. Low-carbon, low-alloy pipeline steels like X52, X60, and X65 comprise the existing fuel transmission pipeline infrastructure. However, similar carbon steels, used in the ethanol processing and production industry, were found to exhibit stress corrosion cracking (SCC) in ethanol service. Prior work has shown that contaminants absorbed by the ethanol during distillation, processing or transport could be the possible determinants of SCC susceptibility; 200 proof ethanol alone was shown not to cause SCC in laboratory studies. To ensure the safety and integrity of the pipeline system, it was necessary to perform a mechanistic study of SCC of pipeline steel in fuel grade ethanol (FGE).
The objective of this work was to determine the environmental factors relating to SCC of X65 steel in fuel grade ethanol (FGE) environments. To accomplish this, a systematic study was done to test effects of FGE feedstock and common contaminants and constituents such as water, chloride, dissolved oxygen, and organic acids on SCC behavior of an X65 pipeline steel. Slow strain rate tests (SSRT) were employed to evaluate and compare specific constituents' effects on crack density, morphology, and severity of SCC of X65 in FGE. SCC did not occur in commercial FGE environments, regardless of the ethanol feedstock. In both FGE and simulated fuel grade ethanol (SFGE), SCC of carbon steel was found to occur at low water contents (below 5 vol%) when chloride was present above a specific threshold quantity. Cl- threshold for SCC varied from 10ppm in FGE to approximately 1 ppm in SFGE. SCC of carbon steel was inhibited when oxygen was removed from solution via N2 purge or pHe was increased by addition of NaOH. During SSRT, in-situ¬ electrochemical measurements showed a significant role of film rupture in the SCC mechanism. Analysis of repassivation kinetics in mechanical scratch tests revealed a large initial anodic dissolution current spike in SCC-causing environments, followed by repassivation indicated by current transient decay. In the deaerated environments, repassivation did not occur, while in alkaline SFGE repassivation was significantly more rapid than in SCC-inducing SFGE. Composition and morphology of the passive film on X65 during static exposure tests was studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results showed stability of an air-formed native oxide under static immersion in neutral (pHe = 5.4) SFGE, and dissolution of the film when pHe was decreased to 4.3. XPS spectra indicated changes in film composition at high pHe (near 13) and in environments lacking sufficient water. In light of all results, a film-rupture anodic-dissolution mechanism is proposed in which local plastic strains facilitates local breakdown of the air-formed oxide film, causing iron to dissolve anodically. During crack propagation anodic dissolution occurs at the crack tip while crack walls repassivate preserving crack geometry and local stress concentration at the tip. It is also proposed that SCC can be mitigated by use of alkaline inhibitors that speed repassivation and promotes formation of a more protective Fe(OH)3 film.
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Almebäck, Julia Linnea Hildur, Amanda Edberg, and Rafa Shah. "Corrosion in Pulp Mills : Material Selection for an Evaporation Plant." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277877.
Full textAbstract:
Corrosion is a global problem which leads to both economicalct on the environment as well as other negative social and ethical aspects. Sodra Cell Monsteras, one of the largest producer of pulp in the world, suffers from corrosion problems in their evaporation plant. Problems with corrosion can be handled with an effective material selection process, where suitable materials for specific conditions is discovered. The purpose with this report is to investigate the evaporation plant at Sodra Cell and its specific conditions, including environment and temperature. Also to investigate different types of corrosions common in pulp mills and how these can be prevented, as well as how materials behave under corrosive circumstances. The information is later to be used in a detailed material selection process, which is handled in this report but also should work as a foundation for Sodra Cell Monsteras for future material selections. The material selection process in this report is performed according to Ashby's method, with CES Edupack as a supporting tool. The duplex steels, especially EN 1.4485 and EN 1.4362, showed to be the best suitable materials. However, to do a fair judgment and to choose one material, one should do a complete cost efficiency analysis, as well as decide a specific required pitting resistance equivalent number (PREN).Korrosion ar ett globalt problem som leder till både ekonomiska förluster, negativ miljöpåverkan samt andra negativa sociala och etiska aspekter. Södra Cell Mönsterås, en av världens största producenter av pappersmassa, har problem med korrosion i sin indunstningsanläggning. Korrosionsproblem kan lösas genom att ha en effektiv materialvalsprocess där rätt material för specifika förhållanden och ändamål används. Syftet med den här rapporten är att undersöka vilka specifika förhållanden som råder i Södra Cells indunstningsanläggning, däribland miljö och temperatur. Men även att undersöka vilka olika korrosionstyper som vanligen förekommer i massaindustrin, hur dessa kan förhindras samt hur olika material beter sig under korrosiva förhållanden. Informationen ska kunna användas som underlag i en utförlig materialvalsprocess, som även hanteras i denna rapport men kan även fungera som en grund för Södra Cell Mönsterås framtida materialval. Materialvalsprocessen i denna rapport är utförd enligt Ashbys metod, med CES Edupack som ett hjälpmedel. Det visar sig att Duplexa stål, speciellt EN 1.4485 samt EN 1.4362 är material som lämpar sig bäst för användning i den korrosiva miljön i indunstningsanläggningen. För att kunna göra en rättvis bedömning och välja ut ett av dessa material, bör en fullständig kostnadsanalys utföras, samt att det bör klargöras vilket specifikt värde för "pitting resistance equivalence number" (PREN) som krävs.
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Li, Guangfu. "The performance of transition joints in high temperature water environments." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362413.
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Salinas-Bravo, Victor Manuel. "Pitting and stress corrosion cracking of duplex stainless steels." Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493165.
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Jönsson, Martin. "The atmospheric corrosion of magnesium alloys : influence of microstructure and environments /." Stockholm : Kemi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4545.
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Benyahya, Matlub Mohammed. "Corrosion behaviour of austenitic steels in basic thiosulfate gold leaching environments." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44373.
Full textAbstract:
Thiosulfate leaching of gold is being proposed as an environmentally friendly alternative to
the dominant cyanide-leaching technology. Thiosulfate leaching is, to a large extent, dependent
on the availability of materials of construction. There are indications that materials of
construction could be a major issue if not addressed; particularly their corrosion resistance.
Therefore, understanding the corrosion behaviour of materials of construction, such as stainless
steels, in this medium is critical to the future development and acceleration of industrial
implementation of this new technology.
The debate surrounding the use of cyanide in the mining industry has fuelled considerable
investigation into the development of some more environmentally benign alternatives. The
thiosulfate process has been widely accepted by researchers around the world as a potential
alternative lixiviant for the leaching and recovery of gold. Moreover, sodium thiosulfate is
relatively nontoxic and, consequently, from an environmental standpoint, has a definite
advantage over cyanide. Comparing reagent unit costs, sodium thiosulfate is far cheaper than
sodium cyanide. Thus, with similar or even slightly higher lixiviant consumption, the application
of thiosulfate for gold recovery can be economical and compete directly with cyanidation.
‘Rust never sleeps!’, so says a popular song. In a broad sense, corrosion appears to be the
reverse process of extraction. In this process, most metals tend to presume a chemicallycombined
state rather than a pure metallic form achieving, in the process, the most energy stable
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form possible. Thus, freshly-extracted metals, as well as finished metallic products, tend to deteriorate when exposed to certain environments. Thiosulfate has been identified as such an environment in mining and other industries, where thiosulfate-dominated processes, such as thiosulfate gold leaching, are strongly believed to highly promote localized corrosion.
In this work, the pitting corrosion behaviour of 304- and 316-type stainless steels were studied using cyclic polarization techniques and electrochemical impedance spectroscopy (EIS) run on a thiosulfate system at several pH and temperature levels in the presence and absence of chloride ions. The stainless steels studied were found to show similar general corrosion behaviour with varying degrees of corrosion resistance to pitting as control variables were regularly perturbed. The results indicate that SS316 has a relatively lower corrosion rate and is more resistant to localized corrosion than SS304 under the conditions considered.
The presence of thiosulfate seems to activate both anodic and cathodic current densities of steel in chloride solutions. The higher the thiosulfate concentration is, the greater the current densities. In addition, for both alloys, the corrosion rate generally increases as the magnitude of the variables is increased; except when the content of chloride ions is altered. Thiosulfate seems to promote passivation in the presence of chloride ions and deter interaction of those ions with the surface of the metal alloys by the formation of an adsorption layer of sulfur that seems to protect the metal surface.
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Khan, Maqsood Ahmad. "Titanium alloys : in-vitro corrosion and wear within varying biological environments." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266093.
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Jönsson, Martin. "The Atmospheric Corrosion of Magnesium Alloys : Influence of Microstructure and Environments." Doctoral thesis, KTH, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4545.
Full textAbstract:
The low density and high specific strength of magnesium alloys have created a great deal of interest in the use of these alloys in the automotive and aerospace industries and in portable electronics. All of these industries deal with applications in which weight is extremely important. However, an obstacle to overcome when using magnesium alloys in engineering applications are their unsatisfactory corrosion properties. This thesis is devoted to the atmospheric corrosion of the two magnesium alloys AZ91D and AM50, in particular the ways the microstructure and exposure parameters of these alloys influence their corrosion behaviour. The work includes both laboratory and field studies. The results obtained show that the microstructure is of vital importance for the corrosion behaviour under atmospheric conditions. The microstructure of magnesium-aluminium alloys contains different intermetallic phases, e.g. Al8Mn5 and β-Mg17Al12. The local nobility of these intermetallic phases was measured on a submicron level in an atmospheric environment. It was shown that particles of the Al-Mn type exhibit the highest Volta potential among the microstructure constituents of the AZ91D magnesium alloy. Further, it was shown that the Volta potential was highly dependent on the aluminium content of the magnesiumaluminium phases in the surface layer. When thin electrolyte layers are present, CO2 diffuses readily to the surface forming magnesium carbonate, hydromagnesite. The CO2 lowers the pH in areas on the surface that are alkaline due to the cathodic reaction. This stabilises the aluminium-containing surface film, the result being increased corrosion protection of phases rich in aluminium. Both in the laboratory and under field conditions the corrosion attack was initiated in large α-phase grains, which is explained by the lower aluminium content in these grains. The thin electrolyte film, which is formed under atmospheric conditions, decreases the possibility of galvanic coupling of alloy constituents located at larger distances from each other. Thus the cathodic process is in most cases located in the eutectic α-/β phase close to the α-phases, instead of in intermetallic Al-Mn particles, even though the driving force for the initiation of the corrosion attack in Al-Mn particles should be high, due to their high nobility.QC 20100802
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Sandana, Daniel. "Stress corrosion cracking of pipeline steels in contaminated aqueous CO₂ environments." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3396.
Full textAbstract:
This work addresses the risk of Stress Corrosion Cracking (SCC) in CO₂transport pipelines. The susceptibility of X80 pipeline steels in aqueous CO₂environments in the presence of nitrates and sulphites is investigated using electrochemical potentiodynamic tests and Slow Strain Rate Tests (SSRT) at 23 and 75°C. The electrochemical measurements showed that in CO2-free and CO₂-saturated systems, the material presents an active-passive transition in bicarbonate/carbonate solutions with nitrate and sulphite. This indicated that SCC is possible in all the test environments. SCC occurred in bicarbonate/carbonate solutions with nitrates and sulphites at 75°C, both under CO₂-free and CO₂-saturated conditions. SCC severity declined as the potential moved towards the free corrosion potential. Cracking was still observed at +50 mV from Ecorr. The cracking mode in the active domain was transgranular for all the systems. In CO2-free systems, the severity and cracking mode in the HCO₃--CO₃² --H₂O and NaNO₃-HCO₃--CO₃² --H₂O systems was similar in the active-passive transition domain at 75°C. Crack growth was controlled by anodic dissolution and the crack mode was intergranular for both systems. At high pH ( > 9), the overall cracking mechanism remains dominated by the HCO₃--CO₃² --H₂O system even in the presence of nitrates. The addition of sulphites to bicarbonate/carbonate solutions however decreased the severity of cracking and shifted the cracking mode to transgranular. In CO₂-saturated systems, the SCC susceptibility in all test environments decreased with lower pH. Yet the highest susceptibility to cracking in the active-passive domain was identified in the nitrate-containing systems. With the drop in pH, nitrate SCC becomes the dominant mechanism when nitrates are present in the HCO₃--CO₃² --H₂O system. The addition of CO2 shifted the mode of cracking to transgranular in the active-passive domain in the pure bicarbonate/carbonate solution.
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Huynh, Ngoc Huu. "The Inhibition Of Copper Corrosion In Aqueous Environments With Heterocyclic Compounds." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15951/1/Ngoc_Huu_Huynh_Thesis.pdf.
Full textAbstract:
Benzotriazole (BTAH) has been used as a corrosion inhibitor for copper and copper-, based alloys for more than 40 years. It has been successfully employed for the, prevention of both atmospheric corrosion and particularly for the protection of, copper under immersed conditions. Whilst BTAH is an excellent inhibitor in alkaline, solution its efficiency drops off markedly as the pH decreases. It was hypothesized, that a possible way to increase surface adsorption and subsequent better inhibition, over a wide pH range might be through the preparation of derivatives, particularly, carboxybenzotriazoles and alkyl esters of these compounds.
In this work the following techniques: weight loss measurements, potentiodynamic, polarisation, SERS spectroscopy, electrochemical impedance spectroscopy and, coulometry were employed to investigate the inhibition efficiency of 4- and 5-, carboxybenzotriazole and their alkyl ester for copper corrosion. Molecular modelling, was also investigated as a tool for inhibitor design.
Studies on 4- and 5- carboxybenzotriazole (CBT) showed that the inhibition, efficiency for copper corrosion in aerated acidic sulphate solution of each isomer was, pH, concentration and time dependant. At lower pH the 5-isomer is the better, inhibitor and this behaviour continues at higher pH. The anti-tarnishing test showed, that whilst both isomers exhibited these properties, 5-CBT was once again the, superior inhibitor.
It was found that a commercial mixture of the octyl esters of 4- and 5-, carboxybenzotriazole inhibits copper corrosion in sulphate environments open to air., The inhibition efficiency of the ester mixture at the lx10-4 M level (pH - 0) is 98%, which compares very favourably with that for BTAH (- 50%). With respect to other, alkyl esters of 4- and 5-carboxybezotriazole, hexyl, butyl and methyl, it was found, that all of these inlibited copper corrosion in sulphate environments open to air. In, each case the inhibition efficiency is concentration, pH and time dependent. Both, coupon tests and EIS measurements indicate that inhibition efficiency depends on the, length of the alkyl chain. At pH - 0 the inhibition efficiency decreased in the order, octyl >hexyl >butyl >methyl. At higher pH (- 8) the order is reversed. At the 1x104, M level (pH - 0) the inhibition efficiency of each of the alkyl esters is equal to or, better than that for BTAH. At higher pH (- 8) the inhibition efficiency in each case is, reduced in comparison to BTAH. but is still good enough for practical use ( 2 75%)., The inhibitive behaviour of the alkyl esters at low pH can be attributed to, chemisorption through an azole nitrogen of the protonated alkyl esters. The, hydrocarbon chain is also physically adsorbed and the increase in physical adsorption, as the chain is lengthened accounts for the improved inhibition efficiency.
Dry films formed by immersing copper in solutions of alkyl esters of, carboxybenzotriazole also inhibit copper corrosion in both strongly acidic (pH - 0), and near neutral (pH - S) sulphate corrodents. The inhibition efficiency depends on, the solvents used to dissolve the esters, solution temperature and immersion time., Aqueous coating solutions furnish the most protective films. Films formed by, CBTAH-BU, CBTAH-HE and CBTAH-OE are more protective than that formed by, BTAH. The inhibition efficiency of the alkyl ester film increases as the alkyl chain is, made longer.
Molecular modeling showed that the optimum crude binding energy (Eblnd), between each protonated ester molecule and the surface varied linearly with the alkyl, chain length. The resulting linear correlation between IE% and E bind for compounds, that are structurally similar suggested that the crude binding energy of a single, molecule with copper may be used to predict the inhibition performance of other, compounds constituting a series.
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Huynh, Ngoc Huu. "The Inhibition Of Copper Corrosion In Aqueous Environments With Heterocyclic Compounds." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15951/.
Full textAbstract:
Benzotriazole (BTAH) has been used as a corrosion inhibitor for copper and copper-, based alloys for more than 40 years. It has been successfully employed for the, prevention of both atmospheric corrosion and particularly for the protection of, copper under immersed conditions. Whilst BTAH is an excellent inhibitor in alkaline, solution its efficiency drops off markedly as the pH decreases. It was hypothesized, that a possible way to increase surface adsorption and subsequent better inhibition, over a wide pH range might be through the preparation of derivatives, particularly, carboxybenzotriazoles and alkyl esters of these compounds. In this work the following techniques: weight loss measurements, potentiodynamic, polarisation, SERS spectroscopy, electrochemical impedance spectroscopy and, coulometry were employed to investigate the inhibition efficiency of 4- and 5-, carboxybenzotriazole and their alkyl ester for copper corrosion. Molecular modelling, was also investigated as a tool for inhibitor design. Studies on 4- and 5- carboxybenzotriazole (CBT) showed that the inhibition, efficiency for copper corrosion in aerated acidic sulphate solution of each isomer was, pH, concentration and time dependant. At lower pH the 5-isomer is the better, inhibitor and this behaviour continues at higher pH. The anti-tarnishing test showed, that whilst both isomers exhibited these properties, 5-CBT was once again the, superior inhibitor. It was found that a commercial mixture of the octyl esters of 4- and 5-, carboxybenzotriazole inhibits copper corrosion in sulphate environments open to air., The inhibition efficiency of the ester mixture at the lx10-4 M level (pH - 0) is 98%, which compares very favourably with that for BTAH (- 50%). With respect to other, alkyl esters of 4- and 5-carboxybezotriazole, hexyl, butyl and methyl, it was found, that all of these inlibited copper corrosion in sulphate environments open to air. In, each case the inhibition efficiency is concentration, pH and time dependent. Both, coupon tests and EIS measurements indicate that inhibition efficiency depends on the, length of the alkyl chain. At pH - 0 the inhibition efficiency decreased in the order, octyl >hexyl >butyl >methyl. At higher pH (- 8) the order is reversed. At the 1x104, M level (pH - 0) the inhibition efficiency of each of the alkyl esters is equal to or, better than that for BTAH. At higher pH (- 8) the inhibition efficiency in each case is, reduced in comparison to BTAH. but is still good enough for practical use ( 2 75%)., The inhibitive behaviour of the alkyl esters at low pH can be attributed to, chemisorption through an azole nitrogen of the protonated alkyl esters. The, hydrocarbon chain is also physically adsorbed and the increase in physical adsorption, as the chain is lengthened accounts for the improved inhibition efficiency. Dry films formed by immersing copper in solutions of alkyl esters of, carboxybenzotriazole also inhibit copper corrosion in both strongly acidic (pH - 0), and near neutral (pH - S) sulphate corrodents. The inhibition efficiency depends on, the solvents used to dissolve the esters, solution temperature and immersion time., Aqueous coating solutions furnish the most protective films. Films formed by, CBTAH-BU, CBTAH-HE and CBTAH-OE are more protective than that formed by, BTAH. The inhibition efficiency of the alkyl ester film increases as the alkyl chain is, made longer. Molecular modeling showed that the optimum crude binding energy (Eblnd), between each protonated ester molecule and the surface varied linearly with the alkyl, chain length. The resulting linear correlation between IE% and E bind for compounds, that are structurally similar suggested that the crude binding energy of a single, molecule with copper may be used to predict the inhibition performance of other, compounds constituting a series.
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Cheong, Kim Hong. "Influence of surface roughness on the pitting corrosion behaviors of stainless steels in different environments." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691159.
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Rizvi, Toor-E.-Aiman. "Fireside corrosion in oxy-fuel environments and the influence of fuel and ash characteristics on corrosion and deposition." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7654/.
Full textAbstract:
The development of advanced techniques (such as carbon capture and storage) for future power plants and the implementation of retrofit technologies to existing ones (like biomass co-firing) in order to reduce pollutant emission, has raised several concerns for the power industry. One such problem, which also forms the basis of this thesis, is the effect of these measures on corrosion and deposition of the boiler heat transfer surfaces. This research work can be divided into two parts. The first part involved studying the corrosion behaviour of a typical waterwall and a superheater material under simulated oxy-fuel environments with and without the influence of an ash deposit. A custom-built, laboratory scale, corrosion rig with the ability to simulate a range of flue gas compositions and temperatures, in addition to generating a heat flux through the specimen, was set up for this purpose. The second part of this work deals with evaluating the properties of a UK power station coal and four biomass samples with the help of laboratory techniques and thermodynamic modelling in order to predict their fusion and deposit forming tendencies in combustion systems. A series of experiments were performed on the corrosion rig to assess the influence of individual variables on the rate of corrosion. The results indicated that the increased concentration of SO2 in oxy fuel combustion due to recycling of the flue gas, can lead to an increase in corrosion rates especially in the presence of reactive alkali containing deposits. Under the conditions studied, the presence of a biomass ash deposit aggravated the corrosive propensity of the environment while coal ash lessened it. With regard to predicting the fusion behaviour of different ashes, the standard ash fusion tests proved inadequate for explaining the relationship between high alkali constituents in biomass ash and the expected higher slagging and fouling tendencies. Simultaneous thermal analysis was more useful in assessing the physical & chemical changes taking place in the ash. Prediction of the fuel behaviour using FactSage thermodynamic analysis showed that ash melting commences at much lower temperatures than those predicted from laboratory techniques. This would help to explain the increased risk of deposition and corrosion linked with burning high alkali containing fuels.
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Houghton, Jennie. "Variation in growth rates across plant families and environments." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/5533/.
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Zemajtis, Jerzy. "Modeling the Time to Corrosion Initiation for Concretes with Mineral Admixtures and/or Corrosion Inhibitors in Chloride-Laden Environments." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30721.
Full textAbstract:
The application of a mineral admixture, or a corrosion inhibitor, or a combination of both are methods used for the corrosion protection for reinforced concrete bridges. The results of a study on evaluation of corrosion inhibitors from three different manufacturers and of concretes with fly ash, slag cement, and silica fume and a concrete with silica fume and a corrosion inhibitor are presented. The specimens were built to simulate four exposure conditions typical for concrete bridges located in the coastal region or inland where deicing salts are used. The exposure conditions were horizontal, vertical, tidal, and immersed zones. The specimens were kept inside the laboratory and were exposed to weekly ponding cycles of 6% (w/w) sodium chloride solution. In addition, cover depth measurements from 21 bridge decks and chloride data from 3 bridge decks were used, together with laboratory data, in modeling the service lives of the investigated corrosion protection methods.
The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates (3LP). Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces.
Modeling the time as a function of probability of the end of functional service life (EFSL) is presented. It has been shown that the distributions of surface chloride concentration, C0, and diffusion coefficient, Dc, are key elements in the model. Model predictions show that the concretes with mineral admixtures provide much better level of protection against moisture and chlorides than the ordinary portland cement concrete alone. Application of a corrosion inhibitor causes an elevation of the chloride threshold resulting in an additional increase in time to EFSL.
More field studies are needed to better estimate distributions of surface chloride concentration and diffusion coefficient of Virginia bridge decks, and to confirm predicted times to EFSL for low permeable (LP) concretes.Ph. D.
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Reyes-Sanchez, Jose 1958. "Biophysical modeling of Agave pacifica under controlled environments." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282475.
Full textAbstract:
Biophysical models were developed for biomass accumulation, transpiration and carbon dioxide (CO₂) assimilation of Agave pacifica as functions of air CO₂ concentration, photosynthetic photon flux (PPF) and irrigation interval. Parameter estimation and validation were performed for the Gompertz's equation for biomass accumulation and for the Penman-Monteith equation for transpiration. A new biophysical model for CO₂ assimilation is proposed consisting of four components: stomatal opening and CO₂ fixation; malic acid accumulation; malic acid depletion; and photosynthetic carbon assimilation. The main and interactive effects of air CO₂ concentration, PPF and irrigation interval on biomass accumulation, transpiration and CO₂ assimilation of Agave pacifica were also determined.
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Pun, Lok Bahadur 1952. "SEDIMENT EXCLUSION FROM POWER PLANT INTAKES." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276848.
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Behrani, Vikas. "Surface Modifications of Steels to Improve Corrosion Resistance in Sulfidizing-Oxidizing Environments." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19708.
Full textAbstract:
Industrial and power generation processes employ units like boilers and gasifiers to burn sulfur containing fuels to produce steam and syn gas (H2 and CO), which can generate electricity using turbines and fuel cells. These units often operate under environments containing gases such as H2S, SO2, O2 etc, which can attack the metallic structure and impose serious problems of corrosion. Corrosion control in high temperature sulfur bearing environments is a challenging problem requiring information on local gaseous species at the surface of alloy and mechanisms of degradation in these environments. Coatings have proved to be a better alternative for improving corrosion resistance without compromising the bulk mechanical properties. Changes in process conditions may result in thermal and/or environment cycling between oxidizing and sulfidizing environments at the alloy surface, which can damage the protective scale formed on the alloy surface, leading to increase in corrosion rates. Objective of this study was to understand the effect of fluctuating environments on corrosion kinetics of carbon steels and develop diffusion based coatings to mitigate the high temperatures corrosion under these conditions. More specifically, the focus was : (1) to characterize the local gaseous environments at the surface of alloys in boilers; (2) optimizing diffusion coatings parameters for carbon steel; (3)understand the underlying failure mechanisms in cyclic environments; (4) to improve aluminide coating behavior by co-deposition of reactive elements such as Yttrium and Hafnium; (5) to formulate a plausible mechanism of coating growth and effects of alloying elements on corrosion; and (6) to understand the spallation behavior of scale by measuring stresses in the scales. The understanding of coating mechanism and effects of fluctuating gaseous environments provides information for designing materials with more reliable performance. The study also investigates the mechanism behind the effect of REs on scale adhesion and sulfidation behavior. Thus, the present work will have a broad impact on the field of materials and coatings selection for high temperature industrial environments such as boilers and gasifiers, and provides information on RE-modified aluminized coatings on carbon steel as an alternative for the use of bulk superalloys under high temperature sulfur bearing environments.
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Harker, N. J. "The corrosion of uranium in sealed environments containing oxygen and water vapour." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627949.
Full textAbstract:
The corrosion of uranium is not simply a topic for fundamental academic dispute, but is is a real problem with serious implications if allowed to occur unchecked. A significant quantity of this material already exists as 'legacy waste' from its use in civilian and military applications. If a renaissance in nuclear power is experienced then more material will be produced that will require effective stewardship [ ]. It is therefore imperative we fully understand how this waste will behave in confined storage environments in order to predict the associated risks it may pose over extended periods of time. The kinetics of uranium corrosion in environments containing water vapour and oxygen have been well investigated and reviewed, however the mechanism by which it occurs remains still unresolved [ , - , ]. For this study, a specially made corrosion rig was constructed that allowed the reaction to be followed by mass spectrometry of the corrosive gas phase along side continuous temperature and pressure measurements of the reaction volume. This allowed the change in environmental conditions surrounding the corroding metal to be observed over time, thereby providing an accurate simulation of the sealed storage conditions uranium may experience. The corrosion product was also analysed using Secondary Ion Mass Spectrometry (SIMS) to determine the primary corroding species for the reaction. This comprehensive analysis has allowed a mechanism to be proposed that accounts for the observed changes and that can be corroborated with results already published in the literature. Discrepancies also exist in the described reaction kinetics and pressure dependence in the reaction between uranium and water vapour [ , " ]. Here this problem is addressed at a microscale, by examining the influence of impurities in the form of carbide inclusions on the reaction [ ]. Samples of uranium contained 600 ppm carbon were imaged during and after exposure to water vapour. The results of this study indicate that carbide particles on the surface of uranium readily react with water ,vapour to form voluminous U03, H20 growths at rates significantly faster than that of the metal. This observation may have implications for previous experimental studies of uranium-water interactions, where the presence of differing levels of undetected carbide may partly account for the discrepancies observed between datasets. Upon completion of the U + H20 reaction within a sealed volume, the metal is left in a H2 environment, where following reaction may then occur: 2 U + 3 H2 ---+ 2 UH3 This reaction can convert the total bulk metal into a pyrophoric powder, providing the supply of H2 is sufficient [ " ]. The inhibition of this reaction is therefore highly desirable. Surface features that could provide preferential initiation sites for the instigation of this destructive reaction were analysed both before and after limited U + H2 reaction. The samples used containing 600ppm carbon; one set prepared by mechanically polishing to a fine grade and the other received a subsequent electropolishing. 81M8 analysis showed that the additional electropolishing resulted in oxide development along the inclusion-metal interface that was not present after only mechanical polishing. Both sets of samples then underwent hydrogen exposure for a limited period under conditions expected to result in UH3 formation. For uranium prepared by only mechanical polishing, the hydride growths were observed to occur in significant numbers and almost exclusively around exposed inclusions. Conversely, preparation involving electropolishing resulted in extremely limited numbers of hydride growth sites not obviously associated with inclusions. These differences in UH3 formation behaviour are attributed to the presence of oxide formed along the inclusion-metal interface resulting from electropolishing, and highlighted how the observed hydride-forming behaviours exhibited by uranium can be significantly altered by the method of surface preparation. In summary, the current PhD has examined in detail the mechanisms and principle parameters controlling the rate of uranium corrosion in scenarios applicable to dry storage. This has been achieved using bespoke analysis systems combined with cutting edge analytical techniques allowing a variety of aspects of this complex reaction to be tested and observed simultaneously.
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Tyreman, C. J. "The high temperature corrosion of metals and alloys in HF-containing environments." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358527.
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Mathew, Mathew T. "Mapping micro-abrasion-corrosion interactions of materials in aqueous and lubricated environments." Thesis, University of Strathclyde, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424356.
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Abdurrahim, Ali A. "Corrosion behaviour of welded joints within chloride and chloride/CO[2] environments." Thesis, Sheffield Hallam University, 2004. http://shura.shu.ac.uk/19190/.
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Electrochemical measurements and metallographic studies were performed on welded carbon steel pipeline materials. Corrosion tests were performed within naturally chloride solution with and without CO[2] additions at ambient temperature. The pH within different environments, chloride solution alone and buffered chloride solution with CO[2] additions was measured at 6.3 +/- 0.3 and 6.2 +/-0.1 respectively. The objective of this study was to evaluate the corrosion behaviour (rates) of carbon steel welds using both traditional and novel electrochemical scanning techniques within two different chloride environments. Corrosion tests were conducted using DC steady state and scanning electrochemical techniques. These tests consisted of linear polarisation resistance (LPR), corrosion potential (Ecorr)} zero resistance ammetry (ZRA), cathodic polarisation (CP) and the scanning vibrating electrode technique (SVET), which were used to semi-quantitatively assess the corrosion activity of the different microstructures, i.e., weld metal (WM), heat-affected zone (HAZ) and parent plate (PP) respectively. Samples were freshly ground before exposure to the different aqueous chloride solutions. SVET was used during these investigations to evaluate preferential corrosion susceptibilities of weldments. SVET results were compared with results from (long term-immersion) DC-based electrochemical corrosion tests. SVET was found to be a sensitive technique with good resolution allowing differences in corrosion response to be determined within hours as compared to other corrosion tests that require several hours to days.
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Han, Jiabin. "Galvanic Mechanism of Localized Corrosion for Mild Steel in Carbon Dioxide Environments." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1258393107.
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Marberg, Mikael. "Climate, grazing and plant interactions : Does climate and grazing shape plant interactions in alpine environments?" Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-75722.
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Increased knowledge of plant interactions is important for our understanding of how ecosystems will respond to climate changes. Using four common low-herb and three tall- herb species as phytometers I measured the net outcome of plant interactions in an alpine environment by a neighbour removal experiment. Grazing and climate were tested as explanatory factors for differences in the outcome of plant interactions, with two altitudes representing different climates. The most important finding in this experiment is that competition is the dominating interaction among plants in this habitat, regardless of plant size, climate and grazing. Climatic exposure and grazing only influenced tall-herb species while low-herbs were mainly limited by competition, presumably for light. These results are important since facilitative interactions and net facilitation in plant communities are often reported to become more common in severe climates.
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Zakharova, Liubov [Verfasser]. "Modelling plant trait variability in changing arid environments / Liubov Zakharova." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1220909432/34.
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Frank, Brian James. "Corn grain yield and plant characteristics in two water environments." Thesis, Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/3280.
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Asher, Stefanie Lynn. "Investigating the mechanism of transgranular stress corrosion cracking in near-neutral ph environments on buried fuel transmission pipelines." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26499.
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Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Committee Chair: Preet M. Singh; Committee Member: Arun M. Gokhale; Committee Member: Miroslav Marek; Committee Member: Naresh N. Thadhani; Committee Member: Richard Neu; Committee Member: Thomas H. Sanders, Jr.. Part of the SMARTech Electronic Thesis and Dissertation Collection.