Rozprawy doktorskie: „Seawater corrosion”

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Speyer, Andrew James. "Wear/corrosion sensing in flowing seawater". Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269992.

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Singh, Harshmeet. "The corrosion behaviour of aluminium alloy B206 in seawater". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/56551.

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Aluminium alloy B206 is one of the strongest and toughest alloys in the cast aluminium family. Although it is light and has excellent low cycle fatigue strength, AA B206 has been known to perform adversely due to its poor corrosion resistance. Thus corrosion has been identified as one of the major issues that jeopardizes the long-term use and performance of B206. The corrosion behaviour of B206 in seawater is studied through immersion testing and electrochemical techniques such as Potentiodynmaic Polarization, Potentiostatic Polarization, Cyclic Potentiodynmic Polarization and Linear Sweep Thermmametry in two different solutions, namely natural seawater and simulated seawater, at various temperatures. Techniques like Optical Microscopy, Energy Dispersive X-ray Spectroscopy and Scanning Electron Microscopy have been used to investigate the microstructure and surface morphology before and after the electrochemical tests. Heat treatment has been performed on the as-received samples using RRA and T7 heat treatment techniques to compare the corrosion behaviour of the former with the latter using electrochemical techniques and image analysis. Lastly, hardness tests have been performed on various heat treated and as-cast samples to establish a comparison in mechanical properties. This study shows that the extent of B206 corrosion depends on the oxidizing nature of the seawater environment i.e. low or high redox potential rather than on the temperature of the seawater. Natural seawater is more aggressive than simulated seawater. Also, heat treatment improved the corrosion resistance as compared to as-cast B206 which was determined by the values of corrosion current density and surface analysis. Furthermore, heat treatment has led to better mechanical properties as determined by hardness tests.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

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Thistlethwaite, Christopher. "Behaviour of massive reinforced concrete sections in seawater". Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/4819cd1e-a5ce-48c2-a982-874196b3e8d9.

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This study combined research available through literature with extensive experimental studies and substantial physical modelling to estimate the remaining ultimate life of large offshore reinforced concrete structures. Although much research has focussed on concrete degradation due to chloride ingress, corrosion of permanently submerged concrete is regarded as negligible due to the long-assumed apparent worst case of tidal or splash zone exposure. Around 350 specimens were tested with a further 200 exposed for further testing by future research groups. Specimens ranged in size from standard cubes to various beam lengths up to 1.5 metres, allowing for material and structural properties to be assessed. My original contribution to knowledge in the sector enhances the fundamental understanding of corrosion in subsea concrete, challenging the generally held belief of negligible corrosion. Results and modelling provides an improved ability to ultimately estimate the longevity of fully submerged offshore reinforced concrete. Throughout this thesis, the results from experimental works, carried out as a direct result of the lack of data or information in literature, are reported, assessed and then utilised to provide updated ultimate life estimations. With the current offshore concrete structures currently coming to the end of their service life, and the likelihood of further offshore development using concrete for the renewables sector, understanding the long-term degradation is vital in determining the most effective decommissioning and derogation options. The research carried out directly provides detailed information of the likely time-to-failure, allowing for an informed decision to be made on operational and decommissioning plans. Experimental work was carried out over four main phases; corrosion initiation due to bulk diffusion of chlorides (Phase I), corrosion propagation in low oxygen environments (Phase II), corrosion in statically and dynamically cracked sections (Phase III) and structural response of heavily corroded individual and lapped bar sections (Phase IV). Phase I work shows a marked difference between submerged exposures to seawater as opposed to NaCl solution, the unsuitability for accelerated testing with seawater and the likelihood of rapid initiation in offshore structures. Further experimental works through Phases II and III found that although exposed to low oxygen concentrations, reinforcement corrosion continued at significant rates. A variation between anode sizes on the reinforcement is noted, but critically the cross sectional area of the steel was still reduced, albeit in fewer locations. Corrosive products were visibly different, with fewer expansive products, if any, present. Additionally, this study further highlights the importance of cracking on corrosion, currently ignored by recent model codes, such as the fib Model Code 2010, up to 0.2mm crack width. A linear relationship was found between crack width and corrosion rates, with cracking above 0.1mm considered significant. The loss of cross sectional area due to propagation was determined for the given environment, and consequently further studies were initiated in an attempt to determine the relationship between this corrosion propagation and the reduced serviceability or ultimate life of concrete beams. Serviceability, defined by beam stiffness, was reduced due to bond loss along reinforcement. Most importantly, however, results prove that the loss of cross sectional area to be the critical influence on loss of ultimate life. Initial estimates on the remaining ultimate life of the large offshore structures support early rough work that the structures would last centuries. This thesis, however, has shown this is due to the ability of concrete structures with such large volumes of steel to continue to ultimately withstand loading at high corrosion percentages and not due to negligible corrosion, or long initiation periods, commonly suggested in submerged, low oxygen environments.

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Masters, G. L. "Crevice corrosion of austenitic and duplex stainless steels in seawater". Thesis, Cranfield University, 1994. http://dspace.lib.cranfield.ac.uk/handle/1826/11288.

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Duplex stainless steels are finding increasing use in seawater applications, but are prone to attack by crevice corrosion. A mechanism of deaeration and acidification is thought to produce locally aggressive conditions within the crevice. A variety of experimental techniques were therefore used to investigate the crevice corrosion resistance of some commercial duplex stainless steels in seawater and other, more aggressive Cr-containing environments. The established marine grade 316L austenitic stainless steel was used for reference purposes. The investigations provided both quantitative data regarding alloy performance, and qualitative observations regarding the attack mechanism. The crevice corrosion resistance of the duplex stainless steels was shown to be superior to that of 316L, and to increase with (Cr + N) content. Electrochemical polarisation scans demonstrated the importance of dissolved 02 in the seawater in maintaining a protective passive film on these alloys. Active peak current density, a measure of the severity of attack, was shown to increase with decreasing pH. In a simulated crevice solution, the duplex alloys were shown to exhibit both a narrower active range and lower peak current density than 316L. Potentiostatic tests showed weight loss to be an order of magnitude lower for the duplex alloys. Measured weight losses were in agreement with those predicted from polarisation data. The technique suggested that cathodic protection potentials as noble as -600 mV (SCE) may be sufficient to protect duplex stainless steels in seawater. Metallographic observation and electron beam analysis showed that the attack mode is potential dependent, with ferrite and austenite preferentially attacked at more active and noble potentials respectively. Real time tests showed that the internal crevice pH of austenitic stainless steel could fall to as low as 1.3. The rise in corrosion current was found to be a reliable indicator of attack, and was consistent with measured weight loss. Potential shifts were found to be relatively insensitive indicators of breakdown.

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Puget, Yannick. "Failure mechanism of polyurethane coated steel subjected to erosion-corrosion". Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287320.

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Baker, Devon Scott. "Understanding the Corrosion of Low-Voltage Al-Ga Anodes". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/53835.

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Aluminum is an attractive metal for use as an anode in the cathodic protection of steels in seawater due to its low cost and high current capacity. Zinc is often used for its ability to readily corrode, but it has a low current capacity and it operates at very negative voltages, leading to hydrogen generation at the steel cathode, which may cause hydrogen embrittlement. Aluminum can operate at less-negative voltages, therefore reducing hydrogen generation, but it forms a passive oxide film, preventing the anode from corroding. Ga is added to aluminum in small amounts (0.1 wt%) to destabilize this oxide film and allow for active corrosion. The mechanism of how Ga activates Al is still not well-known, though there are prevailing proposals. A previous study noted a difference in behavior between Al-Ga master heats and the alloys that were later produced by re-melting them. This study is focused on characterizing the corrosion behavior of Al-0.1 wt% Ga in synthetic seawater, with samples from a master heat and two subsequent remelts. Galvanostatic, potentiostatic, and open-circuit tests were run, as well as galvanic coupling with 1123 steel. It was found that the remelted anodes behaved more consistently and maintained stable corrosion behavior for longer times than the master heat. X-ray Photoelectron Spectroscopy analysis showed elevated concentrations of Ga inside the oxide layer. The findings support the mechanism in the literature of discrete particles of Ga forming under the oxide film but do not support the mechanism of an amalgam layer formation. This project was funded by NACE International, Virginia Tech project number 457789.
Master of Science

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7

Takeuchi, M. "Fretting and fatigue of a roping steel in seawater". Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384690.

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8

Coimbatore, Dhandayuth Venkatesh. "Cerium chloride inhibition for high strength low alloy steel exposed to sulphide polluted seawater". University of Western Australia. School of Mechanical Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0134.

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[Truncated abstract] Corrosion of steel structures caused by sulphide is a common engineering problem encountered by many industries, such as the petroleum, chemical processing, mining and mineral processing industries. The control of sulphide corrosion is still a controversial topic among corrosion engineers. There is an absence of guideline for a reliable acceptable limit of sulphide level in service and each processing industry has its own empirical values. Selection of inhibitors in the sulphide environment depends on laboratory testing before its actual application in pipelines and reaction vessels. Many investigators have postulated the corrosion mechanisms due to sulphide based on operating envelopes such as pH, chloride, manganese, hydrogen sulphide, sulphate reducing bacteria levels and inhibitor concentration. It is recommended in the literature that the batch dosing of inhibitor and biocide needs to be evaluated in regards to sulphide reducing bacteria (SRB) level, which may produce sulphide concentrations up to 2000 ppm. Although sulphide scale formation may protect the base metal by providing a physical barrier, the detrimental effects of sulphide are often inevitable, such as stress corrosion cracking, hydrogen embrittlement, etc. Currently, there are many chemicals that are used as inhibitors to prevent corrosion by scavenging the sulphide from the environment. Cerium, a rare-earth element, is not used as inhibitor in the sulphide environment. Also, there are no previous research findings on the effects of compounds of rare-earth metals, such as cerium chloride (CeCl3), in sulphide environment. This research examines the corrosion behaviour of 0.4Mo-0.8Cr steel, a High Strength Low Alloy (HSLA) steel, in sulphide-polluted artificial seawater with the addition of CeCl3 and glutaraldehyde. ... It is postulated that the moderate inhibiting effect of CeCl3 is due to the scavenging effect thereby forming Ce2S3 complex. Further reaction of sulphide with steel resulted in ferrous sulphide, leading to an increased corrosion rate. It is also concluded that the CeCl3 interferes with both anodic and cathodic reactions in deaerated conditions. Addition of glutaraldehyde in the sulphide-polluted seawater was found to decrease the corrosion rate. According to the electrochemical measurements conducted, the concurrent addition of glutaraldehyde and CeCl3 appeared to have an added effect on reducing the corrosion of the steel, as evidenced by the increase of the open circuit potential during the short-term testing. From the weight loss measurements after 60 days, sulphide pollution in deaerated seawater was found to increase corrosion rate. This is attributed to the increase of sulphide activity whereby continual dissolution of steel was encountered. From the weight loss tests, it was found that the addition of CeCl3 and glutaraldehyde reduced the corrosion rate of the steel in the solutions containing 0-10 ppm sulphide. There is no noticeable corrosion rate decrease for the solution containing 100 ppm sulphide. The added effect of CeCl3 and glutaraldehyde to the SRB medium has resulted in lower corrosion rates. Further detailed experimentation is required to elucidate the corrosion reduction mechanism in glutaraldehyde-containing environments.

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Sneddon, A. D. "Macrofouling and corrosion of steels and copper-nickel alloys in seawater". Thesis, Robert Gordon University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378071.

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Smallwood, Russell. "Fretting fatigue of steel roping wire in seawater". Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328387.

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Gujarathi, Kedar Kanayalal. "Corrosion of aluminum alloy 2024 belonging to the 1930s in seawater environment". [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3002.

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Carvalho, Maria Leonor. "Corrosion of copper alloys in natural seawater : effects of hydrodynamics and pH". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066304/document.

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Cette thèse, réalisée en étroite collaboration avec le partenaire industriel RSE S.p.A (Italie), s’inscrit dans le cadre du projet européen BIOCOR ITN. Les alliages de cuivre habituellement utilisés dans les circuits de refroidissement de centrales électriques peuvent être affectés par la biocorrosion induite par la formation d’un biofilm. L’objectif de ce travail était d’étudier the comportement à la corrosion de l’alliage 70Cu-30Ni et d’un laiton contenant 2% d’aluminium en milieu marin, dans des conditions industrielles réelles (expériences sur le terrain) et en laboratoire. L’influence de différents paramètres, tels que la solution (eau de mer naturelle filtrée (FNSW) vs eau de mer artificielle (ASW)), la concentration en biomolécules (biomolécules naturellement présentes dans l’eau de mer vs une protéine modèle, l’albumine de sérum bovin (BSA)), l’hydrodynamique (conditions statiques, sous circulation et agitation, électrode à anneau tournant) et le pH (8,0 ; 6,0 et 3,7), a été évaluée. Sur le terrain, le comportement global à la corrosion et les traitements antifouling ont été suivis en utilisant des techniques électrochimiques (potentiel de corrosion Ecorr vs temps, LPR), gravimétriques (pertes de masse) et génétiques. En laboratoire, des mesures électrochimiques (Ecorr vs temps, courbes de polarisation, spectroscopie d’impédance électrochimique), réalisées pendant les toutes premières étapes de formation des couches d’oxydes (1 h d’immersion), ont été combinées à des analyses de surface par XPS et ToF-SIMS. A partir des expériences sur le terrain, l’analyse microbiologique et moléculaire des biofilms formés sur les deux alliages de cuivre dans l’eau de mer naturelle montre la présence des espèces bactériennes Marinobacter, Alteromonas et Pseudomonas. In the case of Al brass, the single experimental loop illustrates both anodic charge transfer and anodic mass transport. A partir des expériences en laboratoire, des modèles sont proposés pour analyser les données d’impédance obtenues à Ecorr. Dans le cas de 70Cu-30Ni, la boucle HF illustre principalement le transfert de charge anodique (diamètre égal à Rta) ; alors que la boucle BF est liée au transport de matière anodique et au blocage partiel de la surface par CuCl. Dans le cas du laiton, la seule boucle expérimentale illustre à la fois le transfert de charge anodique et le transport de matière anodique. Le comportement électrochimique et la composition chimique de surface de l’alliage 70Cu-30Ni sont similaires dans ASW et dans FNSW statiques, du fait de la faible concentration en biomolécules dans FNSW. En comparaison de l’alliage 70Cu-30Ni dans ASW statique sans biomolécules, pour lequel une couche duplex épaisse (couche externe de Cu2O redéposé et couche interne de nickel oxydé) est montrée, la présence de BSA conduit à une couche mixte d’oxydes de Cu et de Ni d’épaisseur plus faible ; les résultats montrent aussi un ralentissement de la réaction anodique et un faible effet d’inhibition de la corrosion en présence de BSA. Sous circulation et agitation, une couche mixte d’oxydes de Cu et de Ni, de très faible épaisseur, est obtenue. Pour les deux alliages dans FNSW, le courant de corrosion icorr estimé à partir de Rta est indépendant de la vitesse de rotation de l’électrode tournante, du fait de la compensation des effets du potentiel et du transport de matière. Pour 70Cu-30Ni dans FNSW statique, la réaction anodique est ralentie à pH acide (effet cinétique). Pour le laiton, un effet d’inhibition de la corrosion est montré à pH acide, et plus le pH est acide, plus la réaction anodique est lente. Pour 70Cu-30Ni, l’épaisseur de la couche d'oxyde augmente avec la diminution du pH, dans le cas du laiton il est indépendante du pH. La composition chimique de la couche d'oxyde semble avoir un effet sur la quantité de protéines adsorbées et l'épaisseur équivalente calculée de la couche organique est très faible (quelques Å pour 70Cu-30Ni et 1 Å pour laiton)
This thesis was carried out in the frame of the BIOCOR ITN European project, in close collaboration with the industrial partner RSE S.p.A. (Italy). Copper alloys commonly used in cooling systems of power plants may be affected by biocorrosion induced by biofilm formation. The main objective of this work was to study the corrosion behavior of 70Cu-30Ni alloy and aluminum brass in seawater environments, under real industrial conditions (field experiments) and in laboratory. The influence of different parameters, such as the solution (filtered natural seawater (FNSW) vs artificial seawater (ASW)), the concentration of biomolecules (biomolecules naturally present in seawater vs a model protein, the bovine serum albumin (BSA)), hydrodynamics (static conditions, under flow and stirring, rotating ring electrode (RRE)) and pH (8.0, 6.0 and 3.7), was evaluated. In field, the overall corrosion behavior and antifouling treatments were monitored using electrochemical (corrosion potential Ecorr vs time, LPR), gravimetric (weight losses) and genetic techniques. In lab, electrochemical measurements (Ecorr vs time, polarization curves, EIS), performed during the very first steps of oxide layers formation (1 h immersion time), were combined to surface analysis by XPS and ToF-SIMS. From field experiments, microbiological and molecular analysis of biofilms formed on both copper alloys in natural seawater indicates the presence of Marinobacter, Alteromonas and Pseudomonas bacterial species. From lab experiments, models are proposed to analyze impedance data obtained at Ecorr. In the case of 70Cu-30Ni, the HF loop illustrates mainly the anodic charge transfer (diameter equal to Rta); whereas the LF loop is related to the anodic mass transport and partial blocking effect by CuCl. In the case of Al brass, the single experimental loop illustrates both anodic charge transfer and anodic mass transport. Similar electrochemical behavior and surface chemical composition of 70Cu-30Ni alloy are obtained in static ASW and FNSW, due to the low biomolecule concentration in FNSW. Compared to 70Cu-30Ni in static ASW without biomolecules, for which a thick duplex oxide layer (outer redeposited Cu2O layer and inner oxidized nickel layer) is shown, the presence of BSA leads to a mixed Cu and Ni oxide layer with a lower thickness; the results also show a slow-down of the anodic reaction and a small corrosion inhibition effect in the presence of BSA. Under flow and stirring, a very thin mixed Cu and Ni oxide layer is obtained. For both alloys in FNSW, the corrosion current icorr estimated from Rta is independent of the rotation speed of the RRE, due to compensated potential and mass transport effects. For 70Cu-30Ni in static FNSW, the anodic reaction is slown down at acidic pH (kinetic effect). For Al brass, there is a corrosion inhibition effect at acidic pH, and the more acidic the pH, the slower the anodic reaction. In the case of 70Cu-30Ni alloy, the oxide layer thickness increases with decreasing pH, whereas for Al brass it is independent of the pH. The chemical composition of the oxide layer seems to have an effect on the amount of adsorbed proteins and the calculated organic layer equivalent thickness is very low (few Å for 70Cu-30Ni and 1 Å for Al brass)

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Ismail, Azzura. "Seawater as a hydraulic fluid : corrosion mechanisms and rates of engineering materials". Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7320/.

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With the increasing demand for environmentally friendly hydraulic fluids in the oil and gas sector, recent advances in hydraulic technology have sparked renewed interest in the application of water instead of oil. For industry, using seawater as a hydraulic fluid would bring many benefits as it can be discharged to the sea. The main corrosion challenges associated with the use of seawater are addressed in this study, particularly on how to extend the material life when corrosion attack is likely to be very severe. On the other hand, the material’s degradation which is common in subsea applications is studied in detail which includes how corrosion mechanisms occur. The materials chosen in this research are those which are used extensively in subsea applications especially in Directional Control Valves (DCV) and piping operating with hydraulic fluids namely: (1) carbon steel, (2) stainless steel, and (3) cermet alloys (WC-Ni and WC-Co). As an active material, carbon steelcorrodes in a general way whereas passive materials such as stainless steel are more prone to localised corrosion which is often more catastrophic and difficult to predict and detect. However, cermets alloys (WC-Ni and WC-Co) which consist of metals and ceramics may exhibit both active and passive trends. Electrochemistry methods which are used in this study provide quantitative data which demonstrates different major corrosion parameters. Generally, temperature, oxygen, anions and pH are the main parameters that affect corrosion attack. In this research the effects of temperature, sulphate to chloride ratio and oxygen were studied on corrosion performance of DCV materials and compared the performance in seawater with a typical commercial hydraulic fluidHW443. From the analysis, it shows that temperature has a severe impact on corrosion rate, but alteration of sulphate to chloride ratio could decrease the corrosion rate close to HW443. Therefore, it is clear that by changing the sulphate/chloride ratio in seawater and adding green corrosion inhibitor similar performance to that compared to the use of commercial hydraulicfluids yet reduce the environmental harm on discharge could be attained. The thesis also presents information ofgeneric interest in corrosion of carbon steel and other materials of interest in subsea environments. Corrosion trends of carbon steel, stainless steel and WC-cermets and their prevalent corrosion mechanisms (from electrochemical analysis) are discussed.

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Tan, KengSoong. "Electrochemical analysis of the erosion corrosion of HVOF aluminium bronze coatings". Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274707.

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徐立沖 i Lichong Xu. "Anaerobic corrosion of mild steel in seawater induced by sulfate-reducing bacteria (SRB)". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242546.

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Todoroff, Peter Kent. "Effect of Turbulence on the Passive Film Growth and Associated Durability of Aluminum Alloys in Simulated Seawater". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83770.

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Turbulent fluid flow at high Reynolds numbers presents significant degradation risks to active-passive metals due to enhanced localized degradation phenomena. A multidisciplinary experiment was proposed to study the relationship between hydrodynamics in fully-developed pipe flow and both the growth and performance characteristics of passive films. Preliminary work was performed to set up (i) an environmental chamber for the experiment, (ii) design a custom wall shear stress sensor and constant temperature anemometer traverse system to monitor hydrodynamic conditions in-situ, (iii) monitor in-situ degradation through an array of ultrasonic thickness transducers, and (iv) acquire data and control the environment via a LabVIEW routine. A validation experiment was conducted on a 1220 mm long experimental section of 45.7 mm inner diameter AA2024-T3 tubing in simulated seawater. Extensive degradation was observed in-situ and confirmed with ex-situ techniques after sequential exposure to fully-developed turbulent flow at an expected wall shear stress of 10 Pa for 180ks (Reynolds number of 122,000) and then at 40 Pa for 630ks (Reynolds number of 262,000). No typical erosion-corrosion hydrological features were observed, however significant pitting and intergranular corrosion were observed with corrosion product caps covering 47% of the total ultrasonic transducers' measurement area. Passive film and pit growth were recorded via ultrasonic thickness measurements with an observed simultaneous decrease in dissolved oxygen content. The validation experiment successfully demonstrated the capability of the designed and constructed sensors for the proposed experiment. Numerous areas of suggested development and research were identified to ensure accuracy and improve interpretation of future experiments.
Master of Science

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Taylor, Ryan Chandler. "Effect of a Simulated Butterfly Valve on the Erosion-Corrosion Rate of Nickel Aluminum Bronze Alloys in Highly Turbulent Seawater". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83818.

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Nickel aluminum bronze (NAB) alloys are used in naval and maritime applications for their excellent corrosion resistance under the influence of seawater. One application involves the use of a NAB butterfly valve within a NAB fluid line to control fluid flow of seawater. Due to the chaotic environment, the corrosion rate of the NAB tubing downstream from the valve increases significantly. The disc angle at which the valve alters fluid flow causes an increase in the fluid velocity and an increase in the turbulence produced on the downstream side of the valve. These fluid conditions contribute to the increase in the corrosion rate of the NAB piping downstream from the valve. This thesis aims to characterize how the change in the disc angle of the butterfly valve causes a change in the erosion-corrosion rate of NAB downstream from the valve. A butterfly valve is simulated using orifice plates of varying diameters to mimic flow conditions at different disc angles. An orifice plate is a simple device with a hole in its center that is designed to restrict fluid flow across a fluid line. Under the same hydrodynamic conditions, the orifice produces nearly the exact same flow coefficients as the valve. At a volumetric flowrate of 0.00757 m^3/s a total of eight locations found along the liquid/metal interface produced pitting sites. The average passivation layer thickness is also measured.
Master of Science

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Xu, Lichong. "Anaerobic corrosion of mild steel in seawater induced by sulfate-reducing bacteria (SRB)". Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B2327315x.

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Wu, Siu-kin. "Corrosion and fouling in heat exchangers cooled by sea water from Hong Kong harbour /". Hong Kong : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12335472.

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胡少堅 i Siu-kin Wu. "Corrosion and fouling in heat exchangers cooled by sea water from HongKong harbour". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31208010.

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Dupuis, Jennifer. "Investigation d’alliages à base de titane de types béta-métastables pour applications marines : cas particulier d’un winch innovant". Thesis, Rennes, INSA, 2014. http://www.theses.fr/2014ISAR0028/document.

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Les alliages de titane sont utilisés dans de nombreux domaines tels que l’aéronautique et l’aérospatial, l’industrie automobile, les plateformes offshore et d’autres applications telles que le biomédical et l’environnement marin. Le choix d’utiliser des alliages de titane repose sur le fait que ces alliages disposent d’un excellent ratio entre la résistance mécanique et la densité ainsi qu’une excellente résistance à la corrosion. Afin d’être employés pour une application marine telle que celle d’un winch innovant, nous avons choisi de travailler sur trois nuances d’alliages de titane β-métastables que sont les alliages Ti-6.8Mo-4.5Fe- 1.5Al, Ti-15Mo-2.7Nb-3Al-0.2Si et Ti-5Al-5Mo-5V-3Cr. Le milieu marin est une atmosphère qui expose les matériaux à des conditions telles qu’elles peuvent générer leur destruction. Divers moyens de dégradation existent. Il était donc intéressant d’évaluer la résistance à la corrosion de ces alliages et de chercher à les protéger contre la corrosion. Le coeur de cette étude repose sur la sélection des alliages de titane susceptibles de répondre au cahier des charges du winch innovant. Des traitements thermomécaniques ont d’abord été définis, puis les alliages ont été caractérisés métallurgiquement et mécaniquement. Ces caractérisations ont permis de connaître les propriétés mécaniques des alliages et de sélectionner les alliages potentiellement employables au sein du winch. Puis des essais de corrosion galvaniques ont été menés via la mesure de différences de potentiel entre les alliages de titane traités et d’autres matériaux susceptibles d’être employé au sein du winch tels que des aciers inoxydables, des alliages d’aluminium et des laitons au plomb. Puis, afin d’évaluer le comportement en corrosion marine du film passif des alliages de titane, des essais de corrosion électrochimiques ont été faits à l’aide d’un dispositif à trois électrodes dans des électrolytes de type chlorure de sodium et eau de mer naturelle. Ainsi des mesures de potentiel libre et de voltammétrie cyclique ont été menées. Le point faible des alliages de titane est le comportement en frottement. Dans ce cas, afin de réduire le coefficient de frottement de ces alliages, il est souvent nécessaire d’effectuer un traitement de surface. Dans cette étude, un traitement thermochimique de nitruration gazeuse a donc été fait sur l’alliage de titane le plus récemment développé parmi les nuances étudiées à savoir le Ti-5Al-5Mo-5V-3Cr. Cet alliage ainsi traité a été caractérisé de façon identique aux alliages traités thermomécaniquement. L’ensemble des essais menés au cours de cette thèse ont permis de déterminer quels alliages de titane parmi ceux étudiés seraient les plus susceptibles d’être employés au sein du winch innovant
Titanium alloys are used in numerous fields as aerospace industry, automotive industry, off-shore industry, and, in several applications such as medical and marine applications. This is due to their good properties like high mechanical strength, low density and excellent corrosion resistance. In order to be used for an innovating winch and so in a marine environment, we have chosen to study three β-metastable titanium alloys which are Ti-6.8Mo-4.5Fe-1.5Al, Ti-15Mo-2.7Nb-3Al-0.2Si and Ti-5Al-5Mo-5V-3Cr. In marine environment, materials are exposed to tough conditions which can generate their destruction. Several modes of degradation exist. It is so interesting to evaluate the corrosion resistance of these alloys and to search their best corrosion protection. So, the heart of the study is to select titanium alloys to meet the specifications of the innovating winch. At first, we defined thermomechanical treatments for those titanium alloys and then these materials were characterized to know their mechanical and metallurgical properties. These tests allowed us to have a well knowledge of mechanical properties of these alloys and to choose which alloys can be employed in a winch. Then, galvanic corrosion tests were made in nitric acid, sodium chloride and sodium hydroxide. We measured potential differences between our treated titanium alloys and other materials which may be used in a winch such as stainless steels, aluminum alloys and leaded brass. Then, in order to evaluate the behavior of the passive film in marine environment of titanium alloys, electrochemical corrosion tests were conducted using a three-electrode method in sodium chloride and natural seawater electrolytes. So, free potential and cyclic voltammetry measurements were conducted. The flaw of titanium alloys is their low friction coefficient. So in order to improve the coefficient of friction of titanium alloys it is useful to do a surface treatment. In this study, a gaseous nitriding thermochemical treatment was done for the most recent developed alloy among the three studied nuances, which is Ti-5Al-5Mo-5V-3Cr. Then this treated alloy was characterized too similarly to the three thermomechanical treated titanium alloys. All of tests we led allowed us to know which titanium alloys with which thermomechanical and surface treatments may be used for the innovating winch

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Howell, William R. N. "An analysis of possible microbiologically influenced crevice corrosion of 316 stainless steel in a seawater environment". Thesis, Monterey, California. Naval Postgraduate School, 1996. http://hdl.handle.net/10945/7939.

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An analysis was conducted of 316 Stainless Steel components which exhibited an unusual degree of crevice corrosion after exposure to seawater for approximately one year. After conducting research into the possible chemical and microbiological mechanisms for the corrosion, a metallurgical and microscopic examination of the components was performed. Results of these examinations indicated that the corrosion observed was probably the result of an interaction between the Gallionella aerobic iron bacteria and the anaerobic sulfate reducing bacteria Desulfovibrio and Desulfomaculum

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Howell, William R. N. (Robert Newton). "An analysis of possible microbiologically influenced crevice corrosion of 316 stainless steel in a seawater environment". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/39622.

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Machuca, Suarez Laura Lizeth. "Microbiologically influenced corrosion of common alloys used for subsea applications". Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/258.

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This project has investigated the susceptibility of offshore construction steels to microbiologically influenced corrosion in seawater, elucidating the effects of temperature, oxygen pressure, exposure time and alloy material composition on biological activity and the corrosion resistance of the selected materials in seawater. Results from this research form the foundations of essential guidelines for design criteria, risk assessment and asset integrity management based on materials selection and preservation treatments in the application to subsea equipment.

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Venkatesan, R. "Studies On Corrosion Of Some Structural Materials In Deep Sea Environment". Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/189.

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Efficient exploitation and conservation of the oceans poses great technological challenges for scientists and engineers who must develop materials, structures and equipment for use in harsh environment of the oceans. For the applications of materials in marine environment, knowledge of the corrosion properties is essential for selection purposes. Presently, effort is being devoted to exploit deep-sea mineral resources. Deterioration of materials in the deep sea is due to the cumulative effect hydrostatic pressure, temperature, pH, dissolved oxygen, salinity and sea current. For the first time, in-situ corrosion measurements on the effect of deep sea environment on some metallic and composite materials were carried out at depths of 500,1200,3500, and 5100 m for 168,174 and 174 days of exposure in the Indian Ocean. Corrosion rate was obtained from weight loss measurements (mm/year) and surface morphology of as-exposed and cleaned specimens of the above materials was studied under scanning electron microscope and ED AX. Galvanic coupling of steel with zinc, magnesium and aluminium were also studied.. Tensile on metal and alloys and tensile, compressive, flexure and ILSS tests on carbon fibre reinforced composite specimen were performed on exposed specimens. XRD studies were conducted on the corrosion product of materials. In order to correlate the performance of materials in deep-sea environment, seawater current and temperature data were also collected at same period Results reveal that the corrosion behaviour of steels is controlled by dissolved oxygen prevailing and corrosion rate corresponds to dissolved oxygen available at these depth levels. This is due to the fact that oxygen acts as a cathodic deploarizer during corrosion reaction of steels in seawater. Corrosion rate of aluminium increases as the depth increases. This is due to the effect of hydrostatic pressure, which reduces the ionic radii of chlorine ions and facilitates easy penetration of these ions into surface layer. Titanium, titanium alloy (Ti-6A1-4V) and stainless steels did not show any deterioration at all depths studied. Morphology of as exposed and corroded coupons reveal different features. EDS analyses on exposed specimens are analyzed in light of seawater parameters. Carbon fibre reinforced composite did not show any change in properties like tensile, compression flexural and ILSS compared to control (unexposed) specimens. The deposition of calcium carbonate on galvanically coupled mild steel with zinc, aluminium and magnesium corresponds to availability of calcium in the deep ocean. EDS analyses on exposed coupons did not reveal calcium element below the calcium carbonate compensation depth (CCD) at 3800 m in Indian Ocean. Potentiodynamic polarization studies on some metals and alloys indicate that the behaviour of materials in deep-sea environment is a cumulative effect of all oceanographic parameters. Tensile test results on stainless steels SS-304 & SS-316L), titanium and titanium alloy (exposed) specimens did not show any significant change in their tensile properties and is again attributed to the passive film formed on its surface and nearly zero corrosion rate observed. Microbiological investigations on the exposed materials indicate that except carbon fibre reinforced composite all other metals and alloys harboured bacterial colonies. Results have been used to recommend structural materials suitable for the deep-sea applications.

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Venkatesan, R. "Studies On Corrosion Of Some Structural Materials In Deep Sea Environment". Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/189.

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Efficient exploitation and conservation of the oceans poses great technological challenges for scientists and engineers who must develop materials, structures and equipment for use in harsh environment of the oceans. For the applications of materials in marine environment, knowledge of the corrosion properties is essential for selection purposes. Presently, effort is being devoted to exploit deep-sea mineral resources. Deterioration of materials in the deep sea is due to the cumulative effect hydrostatic pressure, temperature, pH, dissolved oxygen, salinity and sea current. For the first time, in-situ corrosion measurements on the effect of deep sea environment on some metallic and composite materials were carried out at depths of 500,1200,3500, and 5100 m for 168,174 and 174 days of exposure in the Indian Ocean. Corrosion rate was obtained from weight loss measurements (mm/year) and surface morphology of as-exposed and cleaned specimens of the above materials was studied under scanning electron microscope and ED AX. Galvanic coupling of steel with zinc, magnesium and aluminium were also studied.. Tensile on metal and alloys and tensile, compressive, flexure and ILSS tests on carbon fibre reinforced composite specimen were performed on exposed specimens. XRD studies were conducted on the corrosion product of materials. In order to correlate the performance of materials in deep-sea environment, seawater current and temperature data were also collected at same period Results reveal that the corrosion behaviour of steels is controlled by dissolved oxygen prevailing and corrosion rate corresponds to dissolved oxygen available at these depth levels. This is due to the fact that oxygen acts as a cathodic deploarizer during corrosion reaction of steels in seawater. Corrosion rate of aluminium increases as the depth increases. This is due to the effect of hydrostatic pressure, which reduces the ionic radii of chlorine ions and facilitates easy penetration of these ions into surface layer. Titanium, titanium alloy (Ti-6A1-4V) and stainless steels did not show any deterioration at all depths studied. Morphology of as exposed and corroded coupons reveal different features. EDS analyses on exposed specimens are analyzed in light of seawater parameters. Carbon fibre reinforced composite did not show any change in properties like tensile, compression flexural and ILSS compared to control (unexposed) specimens. The deposition of calcium carbonate on galvanically coupled mild steel with zinc, aluminium and magnesium corresponds to availability of calcium in the deep ocean. EDS analyses on exposed coupons did not reveal calcium element below the calcium carbonate compensation depth (CCD) at 3800 m in Indian Ocean. Potentiodynamic polarization studies on some metals and alloys indicate that the behaviour of materials in deep-sea environment is a cumulative effect of all oceanographic parameters. Tensile test results on stainless steels SS-304 & SS-316L), titanium and titanium alloy (exposed) specimens did not show any significant change in their tensile properties and is again attributed to the passive film formed on its surface and nearly zero corrosion rate observed. Microbiological investigations on the exposed materials indicate that except carbon fibre reinforced composite all other metals and alloys harboured bacterial colonies. Results have been used to recommend structural materials suitable for the deep-sea applications.

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Næss, Monika. "EFFECT OF MICROSTRUCTURE AND SURFACE FINISH ON LOCALIZED CORROSION PERFORMANCE OF SUPER DUPLEX STAINLESS STEEL IN SEAWATER". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produksjons- og kvalitetsteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25741.

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Corrosion resistant alloys (CRAs) used in subsea pressure-retaining components must be compatible with production fluids and resistant to pitting and crevice corrosion in seawater. Whereas materials selection in production environments is governed by well-established international standards such as ISO 15156, much debate still exists as of how to determine the seawater localized corrosion resistance of higher grade CRAs such as duplex super duplex stainless steels (DSS and SDSS, respectively). While most industry specifications rely on the ASTM G48 standard to determine localized corrosion resistance, for duplex and super-duplex stainless steels there is no consensus on surface finish prior testing (e.g. polishing or pickling) and test temperature (e.g. 50 °C in NORSOK 630 versus 40 °C in ASTM A923). Moreover, it is unclear whether existing procedures are sensitive enough to determine the onset of deleterious phases such as σ-phase and chromium nitrides. The objective of this investigation was to quantify the seawater pitting corrosion resistance of a type 25Cr SDSS (UNS S32750) and its correlation with microstructure and surface finish before testing. Cyclic potentiodynamic polarization (CPP) testing was used to determine the effect σ-phase on the corrosion response of the system. CPP results were then compared against industry standard practices based on the ASTM G48 Method A test. In addition, CPP tests were conducted at various temperatures, ranging from 25 to 90°C, to determine the effect of deleterious phases on critical pitting temperature (CPT) and overall localized corrosion resistance.The results from this project indicate that the Critical Pitting temperature for standard solution annealed Super Duplex Stainless Steel is 60-70°C. It is also shown that the corrosion resistance is reduced for material that contains sigma phase showing a Critical Pitting Temperature of 40-50°C. The surface treatments seem to have less effect on the values, but pickled surfaces gave a more repeatable result.

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McKinnon, John Motley. "Corrosion Damage Evolution of a Unidirectional Pit". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1463754286.

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Chicuba, Pedro Claudio Francisco. "Assessment of the corrosion behaviour of alloys 825 and 625 in stagnant seawater-effect of temperature and welding". Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27392.

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Alloy 825 has been extensively used as a cladding alloy in the gas and oil industry for process piping up to and including the manifolds, separators, wellheads, risers and valves. The outstanding corrosion resistance of alloy 825 against general and localised corrosion attack is attributed to its high Ni, Cr and Mo content. However, corrosion failures of alloy 825 equipment have been observed in offshore environments. Alloy 825 has good weldability and for applications that require exceptional resistance to corrosion, Inconel filler metal 625 is used as ''overmatching composition''. Nevertheless, there is always a threat of galvanic corrosion when two dissimilar alloys are electrically connected. In this study, the corrosion behaviour of alloy 825, alloy 625 weld and alloy 825 weldment have been investigated. Potentiodynamic polarization curves for the alloys were recorded in synthetic seawater across a range of temperatures (30 to 60°C). Mixed potential theory was applied to determine corrosion potentials, rates of corrosion and predict the galvanic effect of coupling alloy 825 to alloy 625 filler metal via welding. Three standard methods were considered to determine the critical pitting temperature (CPT) for alloy 825. Lastly, long-term immersion tests in seawater were conducted to determine the relationship between the laboratory accelerated tests results and the performance of the alloys under real service conditions. The results from the experimental tests revealed that alloy 825 and alloy 625 weld exhibit outstanding corrosion resistance to uniform corrosion, despite the effect of temperature on the corrosion rate of both alloys. The galvanic effect of coupling alloy 825 to alloy 625 via welding is insignificant. The corrosion morphology of alloy 825 and its weldment is temperature dependent. At temperatures below 45 °C, grain boundary attack was observed in alloy 825 samples, while pitting corrosion was observed at temperatures higher than 50 °C. Alloy 625 weld exhibited only one mode of corrosion attack, namely the selective dissolution of interdendritic phase throughout the test temperature range. There was no agreement between the CPT results for alloy 825 and its weldment obtained using the three standard methods. No correlation was found between CPT determined by laboratory tests and the temperature above which alloy 825 would suffer pitting corrosion in long term seawater exposure tests.

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McGovern, Scott. "The development of embedded sensors to assess the fatigue response of adhesive joints in marine environments". Access electronically, 2007. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20080911.154008/index.html.

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Stipaničev, Marko. "Improved decision support within biocorrosion management for Oil and Gas water injection systems". Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/10304/1/stipanicev.pdf.

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The objective of this work, achieved in the framework of the BIOCOR European Network, has been to provide the operators of Sea-Water Injection System (SWIS) with improved decision support. The implication of biological component on carbon steel corrosion was explored as well as the possible synergy with other elements (mechanical stress, material properties…). This work showed that biogenic sulphide production, a corrosion threat for steel, can have different origins in seawater. The production rate can determine kinetics and morphology of corrosion attack, which might be governed by the type of microorganisms present. The key parameters are the availability of electron acceptors and the surrounding environment temperature. Sulfate-Reducing Bacteria (SRB) exhibit more vigorous attack compared to sulfidogenic bacteria or genera Clostridium, both found in the studied SWIS. Microbial activity also affects the mineralization process naturally occurring on carbon steel surface leading to architectures composed of mixed iron (II) and (III) minerals such as iron sulfides, magnetite, iron oxyhydroxides, chukanovite and green rust (sulfated or carbonated) as well as calcareous deposits. Inner layers of these structures could possibly provide an anaerobic habitat for SRBs, where they can flourish by using sulfate from GR(SO42-) as a terminal electron acceptor for their dissimilatory respiration. This enables continuous degradation of steel. Finally, significance of material microstructure and impact of mechanical stress on corrosion processes was also recognized. Grain boundaries and inclusions are playing a role during the initial stage of corrosion attack. This impact can diminish during the immersion time. An elevated bacterial activity coupled with mechanical stress leads to an increase of material deterioration. However, the mechanisms are not different from those usually observed for unstressed steel. Moreover, sulfidogenic microbial activity does not seem to lead to a failure mechanism related to Stress Corrosion Cracking (SCC). In conclusion, the outcomes indicate the possible situations, which may (or may not) lead to breach the safe operating window for a given SWIS.

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MÁRQUEZ, Marcy Viviana Chiquillo. "Avaliação da resistência à corrosão do aço carbono ASTM 572 Gr50 exposto a óleo cru, água do mar e misturas de óleo/água do mar em condições estáticas e dinâmicas". Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18603.

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Nas diversas etapas processuais da indústria de petróleo – extração, recuperação, armazenamento, transporte e refino, os materiais metálicos são expostos a fluidos corrosivos e solicitações mecânicas. Na etapa de armazenamento, em tanques de petróleo, é possível evidenciar a presença de duas fases, uma oleosa e outra aquosa, que de forma isolada ou associada podem influenciar no processo corrosivo. No transporte de petróleo, apresenta-se o efeito de corrosão-erosão (C-E) gerado pela presença de sais, gases e partículas sólidas que prejudicam a integridade dos equipamentos. Este trabalho teve como objetivo avaliar o comportamento do aço ASTM 572 Gr50 exposto a óleo cru, água do mar e misturas desses fluidos em diferentes proporções; sob condições estáticas simulando tanques de armazenamento e dinâmicas, visando simular transporte dos fluidos. Foram realizados testes de imersão do aço em diferentes fluidos corrosivos (óleo cru, água do mar, misturas de óleo e água do mar nas proporções de 20 e 50 % em volume de água do mar), ao longo de 60 dias em condições estáticas e dinâmicas. O processo corrosivo do material exposto aos diferentes meios foi analisado através de ensaios de perda de massa, análises eletroquímicas de potencial de circuito aberto (PCA), polarização potenciodinâmica e espectroscopia de impedância eletroquímica (EIE). A morfologia da corrosão foi avaliada através de microscopia eletrônica de microscopia óptica (MO) e varredura (MEV). Testes de microdureza Vickers e análises microestruturais foram realizados para analisar a ocorrência de mudanças nas propriedades mecânicas dos aços. Os resultados evidenciaram a influência do teor de água do mar no processo corrosivo, onde foram observados maiores valores de taxa de corrosão para os sistemas contendo maior proporção de água do mar. O mecanismo de C-E, observado nos sistemas dinâmicos mostrou ser mais agressivo que o processo de corrosão isoladamente (sistemas estáticos) o que foi observado por meio dos maiores valores de taxa de corrosão e também pelas morfologias de processo de deterioração da superfície vista por MO e MEV, onde cavidades de maior longitude e pites internos foram observados para os sistema sujeitos ao processo de C-E. Não foram observadas mudanças significativas na microestrutura do material após exposição às condições de fluido estudadas. Os resultados de MEV mostraram a presença de corrosão localizada em todos os sistemas, inclusive para os sistemas contendo apenas óleo cru, que apresentou baixa taxa de corrosão. Os ensaios eletroquímicos de PCA, polarização e EIE realizados com os eletrólitos advindos dos ensaios de imersão (fase aquosa) mostraram que o contato entre fluidos distintos (óleo e água do mar) sob condições de agitação, promove uma intensa troca composicional entre os meios, aumentando a agressividade e modificando a interação metal/meio. O eletrólito proveniente do sistema dinâmico contendo mistura de óleo e água do mar (50%) foi o que se mostrou mais agressivo, visto que no ensaio de polarização linear apresentou o maior valor de densidade de corrente anódica.
In the various procedural stages of the oil industry - extraction, recovery, storage, transportation and refining, metal materials are exposed to corrosive fluids and mechanical stresses. In oil tanks of the storage step, it is possible to demonstrate the presence of two phases, an oily and other aqueous, which isolated or associated, can influence the corrosion process. In the oil transport the corrosion-erosion (C-E) effect is present and it is generated by the presence of salts, gases and solid particles that can influence the integrity of the equipment. This study aimed to evaluate the behavior of ASTM 572 GR50 steel exposed to crude oil, sea water and mixtures of these fluids in different proportions; under static conditions simulating storage tanks and dynamic conditions, aiming to simulate fluid transport. Immersion tests were performed in different corrosive fluids (crude oil, seawater, oil mixtures and sea water in the proportions of 20 to 50% by seawater volume) for 60 days, under static conditions and dynamics. The corrosive process of material exposed to different media was analyzed by mass loss tests and electrochemical analysis of open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The morphology of corrosion was assessed by microscopy optical (OM) and scanning electron microscopy (SEM). Vickers microhardness testing and microstructure analysis were performed to examine the changes occurring in the mechanical properties of steels. The results showed the influence of the seawater content in the corrosion process, in which were observed higher corrosion rate values for the systems containing higher proportion of seawater. The C-E mechanism, seen in dynamical systems proved to be more aggressive than corrosion process isolated (static systems) which was observed by means of higher corrosion rate values and also by the morphologies of the surface deterioration process seen by OM and SEM, where the greater length and internal cavities pits were observed for the system subject to the C-E process; There were not significant changes in the microstructure of the material after exposure to conditions fluid studied. SEM results showed the presence of localized corrosion on all systems, including systems containing only crude oil, which showed low corrosion rate. Electrochemical test OCP, polarization and EIS conducted with electrolytes arising from immersion tests (aqueous phase), showed that the contact between different fluids (oil and seawater) under agitation conditions, promotes an intense exchange compositional between the fluids, increasing the aggressiveness and modifying the metal/media interaction. The electrolyte from the dynamic system containing a mixture of oil and seawater (50%) was the more aggressive electrolyte, as can be seen in the linear polarization that showed the highest value of anodic current density.

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Costa, Jeremias de Freitas. "Avaliação de aminoácidos como inibidores de corrosão para cobre em meio de água do mar artificial". Universidade do Estado do Rio de Janeiro, 2013. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=8914.

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Inibidores de corrosão são substâncias que quando adicionadas a um meio agressivo, diminuem ou previnem a reação de oxidação de um metal com este meio e/ou as reações de redução de espécies presentes no meio. Para a inibição da corrosão de cobre e suas ligas em meios ácidos ou neutros, o inibidor mais empregado é o benzotriazol (BTAH), o qual forma complexos com os íons Cu (I) e Cu (II) na superfície do metal, diminuindo o processo corrosivo. A preocupação com a preservação ambiental e a toxicidade de inibidores de corrosão vem sendo discutida na literatura. Vários estudos têm-se intensificado usando aminoácidos, como proposta para substituição ao BTAH, considerado tóxico. Entre os aminoácidos estudados, dois apresentavam enxofre em suas moléculas (cisteína e metionina) e um outro sem heteroátomo na cadeira lateral (glicina). As concentrações variaram entre 10-2 a 10-4 mol/L e pH da solução entre 7,2 e 8,4. Foram realizadas medidas gravimétricas (ensaios de imersão total) e técnicas eletroquímicas, tais como polarização potenciodinâmica e espectroscopia de impedância eletroquímica. A caracterização morfológica da superfície do substrato após os ensaios de imersão total (743 horas) foi feita por meio de microscopia eletrônica de varredura (MEV), espectroscopia de raios X por dispersão de energia (EDS ou EDX) e difração de raios X (DRX). Embora os resultados com aminoácidos tenham sido sempre muito inferiores àqueles obtidos na presença de BTAH, comportamentos semelhantes em função da concentração dos aminoácidos puderam ser observados pelos diagramas de Nyquist. Contudo, com exceção dos resultados verificados para o meio contendo cisteína 10-2 mol/L, todas as eficiências de inibição para os meios contendo aminoácidos, obtidas pelos ensaios de imersão total, foram negativas, mostrando que o tempo de exposição também pode ser relevante para o desempenho destes inibidores. Entre todos os aminoácidos testados, os meios contendo glicina apresentaram os piores desempenhos anticorrosivos, inclusive acelerando o processo de dissolução anódica do cobre. Esse resultado pode estar relacionado à faixa de pH das soluções testadas e à solubilidade dos complexos de cobre formados com os aminoácidos, mostrando que uma faixa ótima de pH também deve ser assegurada para aprimorar a ação destes aminoácidos como inibidores de corrosão
Corrosion inhibitors are substances that, when added to an aggressive medium reduce or prevent the oxidation reaction of a metal with such medium and / or the reduction reactions of specimens present in the medium. For inhibiting the corrosion of copper and copper alloys in acidic or neutral media, the most widely used inhibitor is benzotriazole (BTAH), which forms complexes with the Cu (I) and Cu (II) ions on the metal surface, decreasing the corrosive process. The concern for environmental preservation and the toxicity of corrosion inhibitors have been discussed in the literature. Several studies havebeen intensified using amino acids as a proposal to replace the BTAH, which is considered toxic. Among the amino acids studied, two presented sulfur in their molecules (cysteine and methionine) and another without heteroatom in the side chair (glycine). The concentrations ranged from 10-2 to 10-4mol/L and the pH of the solution variedbetween 7,2 and 8,4. Gravimetric measurements (total immersion tests) and electrochemical techniques, such as potentiodynamic polarization and electrochemical impedance spectroscopy, were performed. The morphological characterization of the substrate surface after the immersion tests (743 hours) was made by means of scanning electron microscopy (SEM), X-rays spectroscopy energy dispersive (EDS or EDX) and X-rays diffraction (XRD ).This effect was probably due to the increased concentration of molecules adsorbed on the metal surface. Although the results with amino acids were always lower than those obtained in the presence of BTAH, similar behaviorsas a function of the amino acid concentration could be observed for the Nyquist diagrams. However, except for the results observed for the cysteine medium containing 10-2mol/L, all the inhibition efficiencies of the media containing amino acids, obtained by total immersion tests, were negative, showing that exposure time may also be relevant to the performance of these inhibitors. Among all amino acids tested, the medium containing glycine showed the worst corrosion performance, accelerating the process of anodic dissolution of copper. This result may be related to the pH range of tested solutions and to the solubility of the copper complexes formed with amino acids, showing that an optimal range of pH must also be provided to enhance the action of these amino acids as corrosion inhibitors

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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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Nehybka, Josef. "Příprava historických pojiv s vysokou odolností proto okolním vlivům". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2019. http://www.nusl.cz/ntk/nusl-401936.

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This master’s thesis is focused on preparation of the mortar mixtures inspired by roman cement with a great resistivity against the corrosion environment, especially a seawater. There were prepared samples of a roman cement containing of pure lime and various artificial pozzolans and natural tuff which were used as pozzolan admixtures. The task of this work is to explore possibility of using pure lime and for example pozzolan admixture which can resist against the corrosive environment like a roman cement. There were prepared a lot of various samples which were tested separately on their mechanical characteristics before and after their exposure of the influence of the corrosive environment. There were used X-ray diffraction analysis for the characterization of a phase composition of the raw materials and some selected samples.

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Kweon, Young-Gak. "Influence de divers paramètres sur la fissuration par fatigue d'aciers de construction dans l'eau de mer sous protection cathodique". Châtenay-Malabry, Ecole centrale de Paris, 1986. http://www.theses.fr/1986ECAP0010.

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Etude du comportement en fissuration par fatigue dans l'eau de mer sous protection cathodique des aciers destinés à la construction de structures off-shore (acier E355, acier non allié 0,06%C, acier allié 1%AL1%CR0,06%C, acier allié 0,43%CU0,06%C). Influence des divers paramètres agissant sur la fatigue-corrosion sous polarisation cathodique: paramètres électrochimiques (marnage, potentiel de polarisation cathodique, circulation et ph de la solution), paramètres mécaniques (cyclage, surcharge), paramètres métallurgiques (composition chimique de l'acier, soudage)

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Itoh, Yoshito, Yasuo Kitane, Mikihito Hirohata, Junya Takemi, 義人伊藤, 安雄北根, 幹人廣畑 i 潤也竹見. "海水中環境を模擬した腐食促進実験による鋼溶接部の腐食劣化特性に関する基礎的研究". 土木学会, 2013. http://hdl.handle.net/2237/18850.

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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 temps
A 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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Al, Bacha Serge. "Générateur d’Hydrogène « vert » pour mobilité légère ou de courte distance Hydrogen generation via hydrolysis of ball milled WE43 magnesium waste Hydrogen generation from ball milled Mg alloy waste by hydrolysis reaction Effect of ball milling strategy (milling device for scaling-up) on the hydrolysis performance of Mg alloy waste Effect of ball milling in presence of additives (Graphite, AlCl3, MgCl2 and NaCl) on the hydrolysis performances of Mg17Al12 Corrosion of pure and milled Mg17Al12 in “model” seawater solution Mechanism of hydrogen formation during the corrosion of Mg17Al12 Hydrolysis properties, corrosion behavior and microhardness of AZ91 "model" alloys SECM investigation of galvanic coupling between Mg and Mg17Al12 in AZ alloys Valorization of AZ91 by the hydrolysis reaction for hydrogen production (Electrochemical approach) Clean hydrogen production by the hydrolysis of Magnesium-based material: effect of the hydrolysis solution". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0312.

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L’hydrolyse des déchets d’alliages de magnésium dans l’eau de mer (i.e. solution aqueuse à 3,5% en masse de NaCl) est une nouvelle approche qui permet à la fois la production de l’hydrogène in-situ et la valorisation de déchets a priori non recyclables. L’objectif de ce travail de thèse est d’optimiser la réactivité de ces déchets par broyage mécanique en présence d’additif(s). Nous avons donc investigué les principaux paramètres de broyage (e.g. atmosphère de broyage, vitesse de broyage, ordre d’ajout des additifs) sur la réactivité d’un alliage WE43 et des déchets d’alliages Mg–Al. Un « scale-up » du procédé de traitement des matériaux a été mené pour explorer la possibilité d’industrialisation du procédé. En outre, nous avons montré que le broyage sous argon est plus avantageux que celui sous hydrogène.Les alliages Mg–Al (plus précisément AZ91) sont les plus utilisés. Dans ces alliages, l’aluminium forme avec le magnésium l’intermétallique Mg17Al12. Pour comprendre le mécanisme de production d’hydrogène à partir d’alliages Mg–Al biphasés (i.e. Mg + Mg17Al12), l’évaluation du comportement de chacun de leurs constituants et de leurs interactions est primordiale. A cet égard, les aspects chimique (i.e. hydrolyse) et électrochimique (i.e. corrosion) de la réaction de Mg17Al12 avec une solution similaire à l’eau de mer et l’effet du broyage en présence d’additifs (e.g. graphite, NaCl, MgCl2 et AlCl3) ont été étudiés. L’évolution de la chimie de surface lors des tests de polarisation a prouvé expérimentalement (par spectroscopie Raman), pour la première fois, la formation d’intermédiaires réactionnels et nous a permis de proposer un mécanisme de formation de H2.L’interaction entre Mg et Mg17Al12 a été explorée en comparant les propriétés de matériaux modèles « AZ91 » (Mg + Mg17Al12). Grâce à la microscopie électrochimique à balayage, l’effet du couplage galvanique est étudié à l’interface des deux composants du matériau. La contribution de Mg17Al12 dans la corrosion des alliages AZ91 a ainsi été clarifiée. L’intermétallique est résistant à la corrosion et accélère la corrosion de Mg en raison du couplage galvanique. Les diverses stratégies de broyage adoptées dans ce travail ont été comparées en les appliquant sur un alliage commercial AZ91. Le matériau traité mécaniquement en présence de graphite et d’AlCl3 présente les meilleures performances en hydrolyse.Finalement, nous avons évalué semi-quantitativement la pureté de H2 (la composition du mélange gazeux et son humidité) produit. L’incidence de certaines conditions expérimentales (e.g. composition de la solution, température, rapport de la masse de poudre au volume de la solution) est reportée. Il a ainsi été montré qu’un réacteur d’hydrolyse de Mg opérant à température ambiante avec l’eau de mer produit de l’hydrogène « propre » in-situ et peut être considéré comme un générateur d’hydrogène « vert » à la demande
The hydrolysis of magnesium alloys wastes in seawater (i.e. 3.5 wt.% of NaCl aqueous solution) is a new approach which allows both in-situ hydrogen production and the valorization of a priori non-recyclable wastes. The objective of this research work is to optimize the reactivity of magnesium-based wastes by ball milling with additives. Therefore, we investigated the effects of the main milling parameters (e.g. milling atmosphere, milling rotation speed, order of the addition of additives) on the reactivity of WE43 alloys and Mg – Al alloys wastes. A « scale-up » of the materials treatment process was conducted to explore the possibility of industrializing the process. In addition, we have shown that milling under argon is more advantageous than under hydrogen.Mg – Al alloys (more precisely AZ91) are the most widely used. In these alloys, Al forms with Mg the intermetallic Mg17Al12. To better understand the mechanism of hydrogen production from these binary Mg – Al alloys (Mg + Mg17Al12), evaluating the behavior of each of their constituents and their interactions is essential. In this regard, the chemical (i.e. hydrolysis) and electrochemical (i.e. corrosion) aspects of the reaction of Mg17Al12 with the model seawater solution and the effect of milling in the presence of additives (e.g. graphite, NaCl, MgCl2 and AlCl3) were studied. The evolution of the surface chemistry during polarization tests has proven experimentally (by Raman spectroscopy), for the first time, the formation of reaction intermediate and has allowed us to propose a mechanism of H2 formation.The interaction between Mg and Mg17Al12 was explored by comparing the properties of model materials of « AZ91 » (Mg + Mg17Al12). Using scanning electrochemical microscopy, the effect of galvanic coupling was studied at the interface of the two components of the material. In view of these studies, the contribution of Mg17Al12 in the corrosion of AZ91 alloys was clarified. The intermetallic is corrosion resistant and accelerates the corrosion of Mg due to galvanic coupling. The various milling strategies adopted in this work were compared by applying them to a commercial AZ91 alloy. Mechanical treated materials with graphite and AlCl3 showed the highest hydrolysis performances.Finally, we semi-quantitatively evaluated the purity of H2 (the composition of the gas mixture and its humidity) produced. The impact of few experimental conditions (e.g. composition of the solution, temperature, ratio of the mass of powder to the volume of solution) is reported. Thus, it has been shown that an Mg hydrolysis reactor operating at room temperature with seawater produces « clean » hydrogen in-situ and can be considered as a « green » hydrogen on demand generator

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Auger, Fernand. "Altération des roches sous influence marine, dégradation des pierres en oeuvre, simulation accélérée en laboratoire". Poitiers, 1987. http://www.theses.fr/1987POIT2018.

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Etude des facteurs de degradation des batiments et ouvrages anciens en pierre calcaire sous influence marine le long de la facade littorale atlantique francaise, en examinant deux situations : zone de marnage, et milieu aerien. Datation des ouvrages et localisation de la provenance des materiaux (carrieres a ciel ouvert et souterraines). Essais divers sur echantillons provenant des carrieres et d'une digue ancienne soumise au marnage, ainsi que de divers batiments historiques en refection (carottage, essais physiques et mecaniques, technique particuliere de mesure de la vitesse du son dans les carottes). Developpement d'un appareil pour la simulation acceleree de l'alteration aerienne, reproduisant les phenomenes naturels observe sur les monuments et sur les falaises naturelles

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Tchalla, Tatiana Siwavi. "Durabilité d'assemblages métal/élastomère en milieu marin". Thesis, Brest, 2017. http://www.theses.fr/2017BRES0121/document.

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Dans des contextes industriels spécifiques, coller un revêtement épais élastomère à des canalisations en acier constitue le meilleur moyen de les protéger de la corrosion en milieu marin. Ce travail de thèse a principalement pour objectif de mieux appréhender le comportement à long terme de ces assemblages acier/colle/revêtement en milieu marin. Deux approches complémentaires ont été définies. La première se base sur des outils statistiques pour traiter les données de caractérisations physico-chimiques des matériaux issus des assemblages utilisés en service depuis plus de trente ans. A partir de ces données hétérogènes (les assemblages sont différents en termes de formulations des matériaux, de procédé de collage et de conditions de vieillissement); des groupes homogènes présentant des scénarios de vieillissement identiques ont été identifiés et les mécanismes majeurs de dégradation du revêtement ont été établis. La seconde approche se focalise sur les assemblages actuellement utilisés dans les opérations de rénovation. Une démarche expérimentale a donc été mise en place en laboratoire afin d’accélérer de manière contrôlée le vieillissement des matériaux et assemblages. Les objectifs sont multiples. Pour chaque matériau (revêtement et colle), il s’agissait de comprendre les mécanismes de dégradation et les cinétiques d’absorption d’eau qui expliquent les évolutions de propriétés mécaniques et physico-chimiques observées au cours du vieillissement. De même, les interfaces ont été caractérisées et les paramètres de procédé qui influent sur la tenue de l’interface métallique ont été identifiés. Cette approche découplée a permis de mieux comprendre le comportement en milieu marin de l’assemblage d’étude à partir de celui des matériaux et interfaces présentes
In some industrial applications, bonding rubber coatings to metallic pipelines is a suitable solution to protect them from marine corrosion. This study deals with the long term behavior of such metallic coated pipelines in a marine environment. Two different approaches have been developed. The first focuses on degradation data of pipelines used for around thirty years in normal service conditions. As these bonded assemblies are different in terms of material formulations, manufacturing processes and aging conditions, statistical tools were used to identify homogeneous groups with identical aging mechanisms. Also, based on these results, the main degradation mechanisms of the rubber coating were established. The second approach focused on pipelines used currently in renovation operations. An experimental methodology was developed in the laboratory to accelerate aging processes. The bulk materials, surfaces and interfaces were characterized physically, chemically and mechanically before and after natural sea water ageing. This enabled an understanding of the mechanisms and kinetics governing adhesion and degradation to be developed. It also allowed the influence of sea water aging on the failure strength of the assembly of interest to be investigated

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Wang, Xiang. "Long-term under-deposit corrosion of carbon steel pipes in seawater environment". Thesis, 2017. http://hdl.handle.net/1959.13/1335468.

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Research Doctorate - Doctor of Philosophy (PhD)
Water injection is the most commonly used method to increase the yield from oil and gas reservoirs. Seawater is typically the most convenient water source, and aquifer water and produced water (recovered from crude oil) or some combination is also used. The water injection pipelines (WIP) usually are carbon steel and often are many kilometres long. Because the insides of the pipes usually are not coated, the adverse operational environment means that internal corrosion is an on-going problem for many water injection pipelines. A corrosion problem of much concern in practice is the severe internal corrosion at the lower part of water injection pipelines in near-horizontal positions, in some cases, severe metal loss threatening the integrity of the pipelines. This type of corrosion is known variously as channelling corrosion, 6 o’clock corrosion, and bottom of the line corrosion. The examination of field observations suggests both under-deposit corrosion (UDC) and microbiologically influenced corrosion (MIC) are likely to be associated with the phenomenon. However, the mechanism of this phenomenon is still not fully understood. This thesis reports the observations of long-term corrosion of model steel pipes in a pilot laboratory study aimed at improving the understanding of development of channelling corrosion in offshore water injection pipelines. Half-pipe steel specimens were exposed continuously to stagnant and simulated deoxygenated seawater in the presence of mixed deposits for up to 365 days. The relative contributions of MIC, UDC and nitrate addition to corrosion development were investigated using four different test environments. The steel specimens were recovered after 12, 180 and 365 days of exposure and the changing surface topography was examined by Scanning Electron Microscopy (SEM) and optical microscope. The evolution of corrosion products were analysed by SEM and Energy-dispersive X-ray spectroscopy (EDS). The pit depths were measured by digital Linear Variable Differential Transformer (LVDT). These techniques present detailed graphical, morphological and chemical results of the corrosion process of mild steel in presence of deposits exposed to deoxygenated seawater. The observations show the synergistic effect of MIC and under-deposit corrosion led to severe localized corrosion. Nitrate addition caused most severe localized corrosion. This is linked to the enhanced MIC and the added nitrate plays the role of a source of critical nutrient. The progression of maximum pitting depth with increased exposure period was evaluated and a preliminary extreme value analysis of variability in maximum pit depth is presented. It is found that extreme value distribution examination shows Gumbel function is not appropriate to describe all the pit depth data. Frechet distribution is a better model to deal with the variability of the deepest pits. Finally, it is proposed that the continuous propagation of broad pits with the initiation of newer pits may explain the ultimate formation of channelling corrosion seen in practical water injection pipelines. Suggestions are provided for industrial practice on controlling rust deposition and MIC. The extreme value analysis of the pit depth data is also important for predicting failure probability due to pitting corrosion. In sum, the results in this thesis have implications for the corrosion management of water injection pipelines in the offshore oil industry.

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Chang, Zhen-Tian Civil &amp Environmental Engineering Faculty of Engineering UNSW. "Corrosion rate of steel reinforcement in concrete in seawater and influence of concrete crack width". 2007. http://handle.unsw.edu.au/1959.4/40539.

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This thesis reports a research of the corrosion mechanism and corrosion rate of steel reinforcement in concrete. Experimental results are presented to compare the corrosion behaviours of steel reinforcement in two blended-cement concretes in seawater. The experimental program included a study of the influence of crack width on macrocell corrosion, an investigation of the procedure for the determination of polarisation curves of steel in concrete and, an evaluation of the corrosion rate of steel in concrete and the influence of crack width as determined by a new polarisation curve analysis. A mechanism is proposed to interpret the different influences, in both the short and long term, of concrete crack width on the macrocell corrosion rate. This mechanism is based on the finding that the corrosion-spread phenomenon is caused by polarisation effects. An oxygen-depletion mechanism is also proposed to explain the much lower macrocell corrosion rate in the slag cement concrete than that in the flyash cement concrete. The procedure for polarisation testing of steel in concrete is found to be critical to obtaining correct polarisation curves. A twotest procedure is verified to be an appropriate procedure and used in this investigation. Experimental polarisation curves of steel in concrete are found to be very different to those expressed by the kinetic Butler-Volmer equation and, this is considered to be a result of the influence of the passive film on the steel surface in concrete. An empirical polarisation formula is developed and its interpretation is based on the postulation of two parallel kinetic processes occurring at the steel/passive-film/concrete interface; one is the active corrosion process and the other is the film growth/dissolution process. The formula is used to model experimental polarisation curves of steel in concrete through curvefitting analyses. Good curve-fitting results are obtained between the polarisation test curves and model curves. The results are used for evaluation of the corrosion rate and Tafel behaviours of steel in the two concretes and for assessment of the influence of crack width on the corrosion rate within the crack zone.

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Escue, William David. "Characterization of the corrosion behavior of high damping alloys in seawater". Thesis, 1987. http://hdl.handle.net/10945/22663.

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Liang, Mengxia. "Characterisation of pitting corrosion for aluminium alloys in natural seawater and freshwater immersion environments". Thesis, 2019. http://hdl.handle.net/1959.13/1407935.

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Research Doctorate - Doctor of Philosophy (PhD)
Aluminium alloys are increasingly being used in structural and commercial infrastructure, such as aerospace, transportation, architecture, defence and marine industries, due to their low density, desired strength, excellent corrosion resistance and other combined properties. For this reason, structural safety is paramount as it can be influenced by the long-term exposure of aluminium alloys to various environments. In wet environments or when in contact with water, aluminium alloys are prone to pitting corrosion, which can be very detrimental. Pitting leads to rapid attacks of discrete areas on the metal surface, while the adjacent surface can remain virtually unaffected. It is vicious and insidious and may result in perforation or contribute to stress-induced failure. For safety and economic reasons, it is important to be able to predict future corrosion and estimate the lifetime of aluminium components. This requires a thorough understanding of the progression of pitting and reliable corrosion data, measured in years, which is essential to building an accurate corrosion prediction model. Many decades of research and investigation have provided for a considerable understanding of the onset and early development of pitting. Unfortunately, relatively few investigations have been dedicated to longer-term (especially that expressed in years) pitting behaviour. In addition, recent research on AA6060-T5 aluminium alloys that are continuously immersed in natural seawater for 2(+), 3, 3.5 and 4 years showed that the long-term pitting corrosion of aluminium alloys is a very complex process. Several different types of pitting morphologies were observed on the metal surface. The development of mass loss at the maximum pit depths as a function of time showed a trend similar to the early part of a bi-modal model, as previously proposed based on long-term pitting corrosion data of steels. In order to have a better understanding of how these complex corrosion morphologies develop and whether this bi-modal model trend can also be applied to other series of aluminium alloys, a group of long-term test programs were performed. This thesis reports observations on the complex, long-term pitting corrosion of AA5005-H34 aluminium alloys in six different immersion environments, all in natural seawater or freshwater. Test coupons were recovered periodically after exposure periods of 1 month, 3 months, 6 months, 12 months, 18 months and 2 years. The corrosion properties including pitting morphologies, corrosion products, mass loss and maximum pit depths for each exposure period were carefully investigated. The changing pitting morphologies and their relationship with the development of mass loss and pit depth as a function of time were analysed and discussed. Extreme value theory was used to analyse the uncertainty of the pit depth data. Also, the likely factors influencing pitting corrosion were discussed. The results showed that pitting morphologies varied significantly in different immersion environments. Within the same immersion environment, the dominant pitting morphology also changed after different amounts of exposure. It was found that the mass loss, the average of the 15 deepest pit depths and the maximum pit depths tended to develop in stages as exposure time increased. Overall, the trends of the datasets for the mass loss and pit depths were similar to that of the early part of a bi-modal trend as a function of time. Corrosion products played an important role in the bi-modal development of pitting. Also, for the deeper pits, specifically those ‘dimple’-like pits that developed in a long-term steady phase, Frechet extreme value distribution showed a slightly better distribution than Gumbel distribution.

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Wu, Bee Fong, i 吳碧峰. "Effect of Corrosion Inhibitors on Corrosion Rates of Mild Steel in 3.5% NaCl Solution and Artificial Seawater Cont- -taining Various Concentrations of NaClO". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/57083511168729976705.

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Streszczenie:

碩士
文化大學
應用化學系
83
NaClO is widely used to eliminate macroorganisms and microorganisms on metal surface in marine enviroment,and prevent the acceleration corrosion that is caused by fouling problems. NaClO is a strong oxidizing agent, may remain in aqueous solutions, and result another severe corrosion problem. In this study, two corrosion inhibitors were chosen to evaluate their inhibitor efficiencies for steel used in 3.5% NaCl solution and artificial seawater containing various concentration (0.1-30 mL/L) of NaClO. The corrosion rate of steel increases with increase concentration of NaClO. Sodium chromate is an effective passivating inhibitor for all test solutions. The corrosion potentials of steel move to more noble (positive) value with the addition of chromate, and corrosion rate can be retarded. Lime is a cathodic inhibitor ,also causes the corrosion potential move positive,and slows down corrosion rate. Lime is not suitable to apply in the aqueous solution containing high concentrate NaClO.

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Chang, Po-Hung, i 張伯鴻. "The optimal control for corrosive effluent from the seawater desalination plant". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/30822934360445542257.

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碩士
國立成功大學
環境工程學系碩博士班
92
Shortly after the inauguration of Wu-Kan seawater desalination plant in Peng-Hu, leaching of materials from cement-mortar linings of the ductile-iron pipes and complaints about red-water from the customers were reported. These were thought to be caused by the aggressive effluent from the RO membrane, which removed most ions from seawater. 　　The purpose of this research is to select the appropriate post-treatment processes to reduce the corrosiveness of the effluent from the desalination plant. First, the literature, concerned with the corrosion control for public water supply, especially for those involved with seawater desalination, was searched. Then the effluent from the Wu-Kan desalination plant was collected and the water quality analyzed. Based on the result from water quality analysis, the appropriate chemicals and dosage needed to restore its chemical stability were predicted theoretically. After chemical conditioning, the water quality was reanalyzed, and the values of various corrosion indexes were calculated. 　　Following the method “Laboratory Immersion Corrosion Testings,” of ASTM G31, the corrosion intensity of the post-treated water was measured. The coupons used in these tests were made of ductile iron. Then correlation between the various corrosion indexes, namely LSI (Langelier Saturation Index), RSI (Ryznar Stability Index), and CCPP (Calcium Carbonate Precipitation Potential), and the lab-measured corrosion rate were evaluated. In addition, alkaline media filter with marble as media and coupling with CO2 addition was also evaluated as alternative post-treatment process. 　　Based on the results from this study, the laboratory immersion corrosion testings are effective for evaluating various post-treatment processes for effluent from seawater desalination plant. However, attention should be paid to providing appropriate mixing and dissolved oxygen in the reacting vessel. 　　Comparing the corrosion inhibition efficiency of the three post-treatment processes, namely lime and carbon dioxide, sodium bicarbonate or carbonate, and alkaline media filter, the results show that lime and carbon dioxide process was very efficient. At Ca(OH)2 dosage of about 60 mg/L and adding sufficient amount of CO2 to keep pH value at about 8.0, the treated water, with LSI value at about 0.2, was chemically stable concerning corrosion. 　　Generally speaking, when the corrosion index of the post-treated water meets the following criteria: LSI 0.2, RSI 8, or CCPP 0, the corrosion rate is limited. Adding only sodium bicarbonate or sodium carbonate, even at very high dosages, was not very effective for corrosion control. These two alkaline agents must be coupled with lime and CO2 in order to adjust the value of corrosion index to the desired range. The water quality of the effluent from the alkaline media filter was similar to that from the lime-CO2 process, and therefore also demonstrated similar corrosion rate. However, the granular size of the alkaline media was found to have profound effect on the performance of the filter. Further, under similar value of corrosion index, the post-treated waters with higher calcium content were found to have lower corrosion rate than those with higher alkalinity value. This probably is related to the formation of protective calcium carbonate layer on metal surface.

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