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1
Azizi, Mazen. "Physikochemische Untersuchungen zur Wirkung von Korrosionsschutzbeschichtungen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2001. http://nbn-resolving.de/urn:nbn:de:swb:14-1003485424984-29051.
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Ziel der durchgeführten Arbeiten war, verschiedene Oxide mit elektrochemischen Methoden in eine Zinkschicht einzubauen. Um den Mechanismus der Dispersionsabscheidung aufzuklären wurden die Feststoffpartikeln durch Zetapotentialmessungen, Partikelgrößenanalyse und die Bestimmung der spezifischen Oberfläche charakterisiert. Außerdem wurde die Abhängigkeit der Partikel-Einbaurate in den abgeschiedenen Zinkschichten von der Art des Bades, der Partikelkonzentration im Bad, der Rührgeschwindigkeit, dem pH-Wert, der Mahlung der Partikeln, der Art des elektrischen Stromes und der Elektrodenanordnung untersucht. Der Anteil an Oxiden in den Zinkschichten wurde mit verschiedenen Meßmethoden analysiert. Die optimierten Dispersionsschichten sind durch verschiedene Methoden charakterisiert worden.
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Bukvic, Tomáš. "Svařování žárově pozinkovaných plechů pomocí hybridní technologie Laser-TIG." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443207.
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Thesis is focused on verification of suitability of Laser-TIG technology for penetrating welding of galvanized sheets, made of WSS M1A 365-A14 50G steel and DC01 steel. Electric arc functions here as a preheating for evaporation of zink layer. Electric current was chosen as a variable parameter of magnitudes 0, 20, 30 and 40 A. Test welds were made, which have been subjected to a tensile test and metallographic evaluation. The positive influence for electrolytically galvanized steel WSS M1A 365-A14 50G was registered and determination of optimal welding parameters was successful. The electric arc also had a positive effect on welding of hot-dip galvanized steel DC01, but at the selected test parameters not enough to achieve a reliable connection.
3
ZIPPERIAN, DONALD CHARLES. "PHYSICAL AND CHEMICAL CHARACTERISTICS OF THE ZINCATE IMMERSION PROCESS FOR ALUMINUM AND ALUMINUM ALLOYS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184123.
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A detailed experimental study has been carried out to investigate the zincate immersion deposition process for 99.99%, 6061, and 356-T6 aluminum samples. In particular, the effect of iron and tartrate in the immersion bath, the aluminum surface preparation, and the relationship of the first immersion step to the second immersion step were investigated by chemical, electrochemical (polarization and rest potentials), and surface analytical scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) techniques. Eh-pH diagrams were constructed to determine the most stable zinc, iron, and aluminum species in solution. These diagrams predict that ferrous and ferric ions, as well as aluminum should form stable complexes with tartrate at the typical immersion deposition conditions (Eh -0.9 to -1.0 and pH 14 to 15). Experimentally, tartrate was found to enhance the dissolution rate of aluminum in highly caustic solutions. The addition of ferric chloride to the immersion bath produced coatings that were more crystalline, and also decreased the amount of hydrogen gas evolved in the second immersion step. The deposition of zinc and iron during the second immersion step was considerably less than that during the first immersion step. The second immersion coating became more adherent as the initial surface roughness decreased, and as grain size was increased the second immersion coating became thicker. For increasing grain size the micrographs for the first and second immersion coatings showed that the coatings became more localized. The second immersion coating thickness and morphology were also dependent upon several first immersion variables, such as bath temperature, immersion time and bath composition. Increased dissolution rates of aluminum in the first immersion produced thinner coatings with a finer crystallite growth. Increased bath temperature and increased first immersion time enhanced the dissolution rate of aluminum. The zinc coating slowed the dissolution rate of aluminum. When zinc was absent from the first immersion bath, the aluminum dissolution was much faster and resulted in thinner coatings upon subsequent second immersion. The molar ratio of zinc deposited to aluminum dissolved was a constant value of 1.1 for both first and second immersions; the molar ratio was also constant for the different aluminum substrates examined in this investigation.
4
Chen, Desong. "Modelling and control of zinc coating." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314906.
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Jain, Rahul. "Investigations on Multiscale Fractal-textured Superhydrophobic and Solar Selective Coatings." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78725.
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Functional coatings produced using scalable and cost-effective processes such as electrodeposition and etching lead to the creation of random roughness at multiple length scales on the surface. The first part of thesis work aims at developing a fundamental mathematical understanding of multiscale coatings by presenting a fractal model to describe wettability on such surfaces. These surfaces are described with a fractal asperity model based on the Weierstrass-Mandelbrot function. Using this description, a model is presented to evaluate the apparent contact angle in different wetting regimes. Experimental validation of the model predictions is presented on various hydrophobic and superhydrophobic surfaces generated on several materials under different processing conditions.
Superhydrophobic surfaces have myriad industrial applications, yet their practical utilization has been severely limited by their poor mechanical durability and longevity. Toward addressing this gap, the second and third parts of this thesis work present low cost, facile processes to fabricate superhydrophobic copper and zinc-based coatings via electrodeposition. Additionally, systematic studies are presented on coatings fabricated under different processing conditions to demonstrate excellent durability, mechanical and underwater stability, and corrosion resistance. The presented processes can be scaled to larger, durable coatings with controllable wettability for diverse applications.
Apart from their use as superhydrophobic surfaces, the application of multiscale coatings in photo-thermal conversion systems as solar selective coatings is explored in the final part of this thesis. The effects of scale-independent fractal parameters of the coating surfaces and heat treatment are systematically explored with respect to their optical properties of absorptance, emittance, and figure of merit (FOM).Master of Science
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Wharton, J. A. "Non-chromate conversion coating treatments for zinc-alloy electrodeposits." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/7611.
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In recent years, the suspected carcinogenic and toxic effects of hexavalent chromium have caused great concern, resulting in the imposition of stringent environmental and workplace regulations in the metal finishing industry. This has lead to the search for suitable alternatives to the chromate formulations. In this investigation molybdate, cerium and permanganate-based solutions have been examined as to their suitability as possible replacements for chromate conversion coatings on zinc-alloy electrodeposits. Investigations have primarily concentrated on producing passive surfaces from molybdate-based immersion processes. The novel conversion coatings have been examined using scanning electron microscopy to elucidate the coating morphologies. Analysis of the molybdate-based coatings has been undertaken to characterise and determine the composition using molybdenum K-edge EXAFS (extended X -ray absorption fine structure) studies. The corrosion behaviours of the treated surfaces have been assessed using neutral salt spray (fog) corrosion tests and electrochemical methods utilising the linear polarisation technique. Findings indicate that simple molybdate, cerium and permanganate-basecdo ating treatments only achieve, at best, corrosion protection by means of a barrier effect, as a result hindering the dissolution processes, thus providing modest improvements to the formation of white and red corrosion products compared with the 'as-plated' zinc-alloy deposits. However, certain molybdate-based treatments, utilising a permolybdate species, appeared to possess additional corrosion resistant behaviours, possibly associated with an inhibition or retarding of the cathodic reactions. Consequently, superior corrosion performances were apparent for a number of the permolybdate coatings in comparison with the simple molybdate treatments, achieving performance characteristics more comparable to a chromate coating, although still at a reduced level of protection. Specific permolybdate coatings were deemed to be capable of providing enhanced corrosion performances, other than by acting solely as barriers to corrosion.
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Wakeham, Steve. "Protective, antireflection coatings for multispectral zinc sulphide." Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402630.
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Marti, Patrick. "Zinc-containing hydroxyapatite coatings for orthopaedic applications." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611527.
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Abibsi, Abdelhafid. "Electrodeposition of corrosion resistant zinc alloy coatings." Thesis, Aston University, 1988. http://publications.aston.ac.uk/11885/.
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With the increase use of de-icing salts on roads for safety, the need for improved corrosion resistance of the traditional galvanized automobile bodies has never been greater. In the present work, Zn alloy coatings (Zn-Ni and Zn-Co) were studied as an alternative to pure Zn coatings. The production of these deposits involved formulation of various acidic (pH of about 5.5) chloride based solutions. These showed anomalous deposition, that is, alloys were deposited much more easily than expected from the noble behaviour of Ni and Co metals. Coating compositions ranging from 0 to about 37% Ni and 20% Co were obtained. The chemical composition of the coatings depended very much on the electrolytes nature and operating conditions. The Ni content of deposits increased with increase in Ni bath concentration, temperature, pH and solution agitation but decreased considerably with increase in current density. The throwing power of the Zn-Ni solution deteriorated as Ni metal bath concentration increased. The Co content of deposits also increased with increase in Co bath concentration and temperature, and decreased with increase in current density. However, the addition of commercial organic additives to Zn-Co plating solutions suppressed considerably the amount of Co in the coatings. The Co content of deposits plated from Zincrolyte solution was found to be more sensitive to variation in current density than in the case of deposits plated from the alkaline Canning solution. The chromating procedures were carried out using laboratory formulated solution and commercially available ones. The deposit surface state was of great significance in influencing the formulation of conversion coatings. Bright and smooth deposits acquired an iridescent colour when treated with the laboratory formulated solution. However, the dull deposits acquired a brownish appearance. The correlation between the electrochemical test results and the neutral salt spray in marine environment was good. Non-chromated Zn-Ni coatings containing about 11-14% Ni increased in corrosion resistance compared to pure Zn. Non-chromated Zn-Co deposits of composition 4-8% were required to show a significant improvement in corrosion resistance Corrosion resistance was improved considerably by conversion coating. However, the type of conversion coating was very important. Samples treated in a laboratory solution performed badly compared to those treated in commercial solutions. Zn alloy coatings were superior to pure Zn, the Schloetter sample (13.8% Ni) had the lowest corrosion rate, followed by the Canning sample (1.0% Co) and then Zincrolyte (0.3% Co). Neither the chromium content of the conversion films nor the chromium state was found to have an effect on corrosion performance of the coatings.
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Tuaweri, Johnnie T. "Zinc and zinc alloy composite coatings for corrosion protection and wear resistance." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/10888.
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Zinc and its alloys are among the most widely utilised metallic coatings for the sacrificial protection of steel. Although excellent in this mode of protection, these coatings are often less durable when subjected to environments of combined wear and corrosion due to their intrinsic relative softness and ductility. A possible and fast growing way of improving the durability of these coating is by the codeposition of inert particles into the zinc and zinc-alloy matrix. The main aim of this research was therefore to improve the durability of zinc and zinc-nickel coatings by the incorporation of inert particles via electrolytic codeposition methods. The first five chapters of this thesis comprise literature review on the electrodeposition of zinc, its alloys and composite electrodeposition in general. A major part of which was dedicated to the review of various conventional methods and parameters such as current density, agitation, temperature, solution composition, bath additives and pH usually investigated in electrodeposition. The experimental work was principally based on DC electrodeposition and was aimed at understanding the deposition behaviour of zinc and zinc-nickel electrodeposition baths, conditions which influence them and solution compatibility to the introduction of silica particles. A systematic study on the deposition behaviour of both zinc/silica and zinc-nickel/silica composite baths was carried out with particular interest on the rate of particle incorporation and the influence of particles on zinc-nickel alloy deposition. The complimentary codeposition behaviour of the nickel and silica particles was observed. The influence of bath additives such as N,N Dimethyldodecylamine (NND) and sodium nitrate on the rate of silica incorporation was also studied. Both additives were found to improve the rate of particle incorporation for the zinc/silica. The morphologies and compositions of the coatings were analysed with the use of SEM and FEGSEM. Corrosion performance studies were carried out in a neutral salt spray chamber and linear polarisation resistance methods used to determine barrier corrosion properties of the coatings. Anodic polarisation studies were also carried out. The results show an improvement in the corrosion performance of these coatings with the addition of silica particles Reciprocating wear tests were used to determine the wear behaviour of the coatings in terms of weight loss. Improvement in wear resistance was not observed in the zinc/silica coatings probably due to the high content of silica in the coatings. Lower silica contents may be required for the desired improvements. However, there were obvious improvements in the wear behaviour of the zinc-nickel/silica coatings due to the presence of the silica particles.
11
Xu, Jing. "Kinetics of corrosion and dross build-up in molten Zn-Al systems." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5294.
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Thesis (Ph. D.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains x, 235 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
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Toff, Mohd Radzi Mohd. "A comparison of the corrosion behaviour of zinc and zinc-5% aluminium coatings." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299628.
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Snider, James M. "Zinc pot bearing material wear and corrosion characterization." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=3716.
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Thesis (Ph. D.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains xx, 272 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 207-208).
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Yixiao, Feng. "ZINC ALUMINUM PHOSPHATE PIGMENTED POLYURETHANE/POLYSILOXANE COATINGS FOR ANTICORROSION." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525950059586312.
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Zhou, Ting. "Electrodeposition of Molybdenum-Based Coatings from Aqueous Alkaline Solutions for Enhanced Corrosion Resistance." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157641/.
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Zn-Mo coatings are very promising environment friendly anticorrosive coatings as replacement materials for cadmium and chromium (VI) based conversion layers. Electrodeposition has become a favorable technique in fabricating coatings due to its low cost, ease of use, and overall experimental control of coating quality. Very little research so far has been done for the electrodeposition of Zn-Mo coatings under alkaline conditions. In this work, Zn and Zn-Mo coatings were electrochemically deposited on stainless steel from an aqueous alkaline citrate solution. An organic compound, vanillin, was added to the electrolyte as a leveling agent for improving interlayer adherence and corrosion resistance of Zn-Mo coatings. Ni-Mo alloys have been known to possess high tensile strength and excellent corrosion protection of steels, and MoTe2 layers have a potential for the application in anticorrosive coatings due to their hydrophobic properties. In this study, MoTe2-Ni-Mo coatings were deposited on stainless steel using both sputtering and electrodeposition methods. These coatings with high corrosion resistance and other desirable properties are in demand in the oil and gas industry since they can protect and thus extend the lifetime of the underlying materials when exposed to aggressive environments. The Zn-Mo and MoTe2-Ni-Mo coatings were evaluated for chemical composition and corrosion behavior using different types of instrumental and electrochemical techniques. The addition of vanillin to the electrolyte did not change the crystalline structure or composition of the Zn-Mo coating, however, the corrosion resistance of the coating was significantly improved by the leveling effect of vanillin during the electrodeposition. The corrosion resistance of the Ni-Mo coating was also enhanced by applying the hydrophobic MoTe2 monolayer on the top surface.
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O'Dell, Simon Paul. "Investigation into the iron-zinc coating constitution and crater evolution in galvanneal." Thesis, Swansea University, 2004. https://cronfa.swan.ac.uk/Record/cronfa42851.
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This thesis investigates the formation of microstructural features, known as craters, within the Galvanneal coating. The work was carried out under laboratory-controlled conditions on a Rhesca hot dip simulator. The thesis examines the nucleation and growth of craters within the coating as it changes from the galvanised coating to the galvanneal coating. The effect of production process parameters upon the nucleation and growth of craters was also investigated. In addition the work also analysed the effect that craters have upon the forming properties of the coating.
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Walsh, Angela Barbara. "The performance of zinc silicate primers in 0.5M sodium chloride." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324927.
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Simmons, M. "Zinc based composite coatings as an alternative to electrodeposited cadmium." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/6788.
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Cadmium coatings are currently applied to steel fasteners used in aerospace applications. At present there are growing concerns, based on cadmium's toxicity and carcinogenicity, which may lead to its eventual banning. The aim of this research, therefore, was to find a possible replacement to electrodeposited cadmium for use on aerospace fasteners. Any replacement coating system should have all of the relevant properties that make cadmium so attractive, but without its obvious shortcomings. These beneficial properties include excellent corrosion resistance in chloride containing media (such as seawater), the ability to offer sacrificial protection to steel, excellent galvanic compatibility with most aluminium alloys and an inherent lubricity. Alternatives proposed and produced in this research are electrodeposited composite coatings containing PTFE particles, based on zinc or zinc alloys. Extensive analysis was carried out in order to characterise the coatings. Composition was determined by a number of methods; gravimetric analysis was used to determine the percentage of codeposited PTFE, while X-ray and X-ray wavelength energy dispersive analysis were used to determine the percentage of alloy element present in these coatings. Coating morphology was investigated by scanning electron microscopy. The sacrificial corrosion performance of each coating in relation to steel was studied using neutral salt-spray tests, while linear polarisation resistance tests gave an indication of their barrier corrosion properties. Galvanic compatibility of the coatings with aerospace grade aluminium alloys was investigated using a zero resistance ammeter. Two different tribological tests, an inclined plane test and a reciprocating wear test, were used to determine the coefficient of friction for the coatings. Finally, linear sweep voltammetry was used to compare the kinetics of electrodeposition from dilute solutions and corrosion in aqueous media for each of the coating systems. The composite coatings were found to offer either similar or slightly reduced corrosion performance to conventional zinc and zinc alloy coatings, but were inferior to commercially electrodeposited cadmium. However, the tribological properties of these coatings demonstrated a marked improvement over cadmium.
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Shah, S. Rehan H. "The deformation behaviour of zinc-rich coatings on steel sheet." Thesis, Cardiff Metropolitan University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314778.
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Chen, Yan. "Galvanic cathodic protection of steel reinforcement using metallized zinc coatings." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/6787.
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Corrosion of steel reinforcement in concrete bridges and parking garages due to the intrusion of chloride ions from deicing salt is a serious problem in northern climates. A number of approaches have been used in the past to mitigate steel corrosion. Cathodic protection is considered to be the only technique to slow down corrosion in salt contaminated concrete to a negligible rate. This is accomplished by either an impressed current anode or a sacrificial anode in the system. The impressed current anode system, with metallized zinc as the anode material, has been used with success on a number of bridges. The sacrificial anode system has been used on a limited number of bridges under marine environment. An impressed current system is difficult to apply to parking garages because of the thickness of concrete cover in these structures. Cover in concrete parking garages is typically much thinner than that used in bridges, and may easily cause electrical shorts between the anode and the reinforcing bar. Systems with sacrifical anodes, commonly referred to as galvanic cathodic protection systems, instead, take advantage of the reduced thickness of concrete cover, thus becoming a feasible form of protection for parking structures. The goal of this research project is to develop a sacrificial anode for cathodic protection of steel reinforcement in parking garages and bridges. Although it is too early to draw conclusions, certain trends have been reported on performance of sacrificial anode systems. So far the results indicate that the effectiveness of galvanic cathodic protection increases with decreasing the thickness of concrete cover. Salt contamination and moisture also increase the effectiveness of galvanic cathodic protection of reinforcement.
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Barnard, Nicholas. "Modelling the localized corrosion effects experienced by electroplated zinc and zinc-4.5 wt.% aluminium steel coatings." Thesis, Swansea University, 2006. https://cronfa.swan.ac.uk/Record/cronfa42335.
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A general modelling approach is described for the numerical simulation of localized corrosion phenomena. The model is demonstrated using several simple cases and compared both to analytical solutions and experimental measurements. The model is intended to operate at the microscopic-mesoscopic length scales and involves two- or three-dimensional field calculations performed in a finite difference computational framework. Limitations and possible extensions to the algorithm are discussed. Experimental work has been reported that demonstrates the effects of microstructural variations within Zn-Al Galfan type coatings on the corrosion behaviour of cut-edge material, i.e. those cases where both the underlying steel and the organic coated Galfan layer are simultaneously exposed to a corrosive environment. An attempt to model the localized corrosion effects in electroplated zinc and hot-dip Galfan coatings has been made. The model combines both diffusive and electrochemical phenomena and describes corrosion effects on micro scale coating layers in NaCl electrolyte. The model predicts the 3D form of electrical potential, localized current densities and concentrations and also the time-dependent degradation of the micro scale coating layer. Results of the prototype model are quantitatively compared with measured current densities obtained from Scanning Vibrating Electrode Technique (SVET) studies. Simulations have been performed to predict the microstructural influence on the corrosion of Galfan coatings cooled at different rates. The model is in good agreement with experimental findings with respect to the cut-edge behaviour of these coatings, although contradicts those SVET measurements made in respect of the surface corrosion performance.
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Varadarajan, Ashok. "Dross formation mechanism and development of wear resistant scraper in 55Al-1.5Si-Zn coating bath." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=6022.
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Thesis (Ph. D.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains xi, 106 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 101-106).
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Hoffman, John Mark. "Zinc coatings for the external protection of ductile iron water mains." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279981.
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Wall, N. J. "The structure and deformation characteristics of zinc coatings on steel strip." Thesis, Bucks New University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373600.
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Chapaneri, Roshan. "A study of hexavalent and trivalent chromium conversion coatings on zinc surfaces." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6690.
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Physical, chemical and corrosion properties of a hexavalent chromium conversion coating (CCC) and that of a commercial third generation trivalent chromium system; Tripass LT1500, on zinc electrodeposited steel has been studied. Moreover, the role of additives has been studied to elucidate film formation and corrosion resistance mechanisms. Micro-cracking and self-repair corrosion protection behaviour commonly associated with hexavalent CCCs has also been investigated. Scanning Electron Microscopy (SEM) studies showed that for both hexavalent and trivalent CCCs were in general, flat with a spherical-like structure and in the case of the former microcracked beyond 122 nm conversion coating thickness. In general, the micro-crack pattern observed e.g. a dense crack network, depended upon the underlying zinc substrate morphology. The study has also demonstrated the effect of SEM imaging and prior specimen preparation conditions on hexavalent CCC micro-cracking and blistering. X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Infrared (IR) data has indicated that the hexavalent CCC film formation appears to be a electrochemical/sol-gel mechanism given the lack of zinc content at surface and subsurface regions within the conversion coating, presence of H2O and in particular the contribution of Cr(OH)3 as opposed to Cr2O3. An alternative film formation mechanism may exist for trivalent CCC given a higher proportion of zinc at surface and sub-surface regions, IR data analysis indicating that chromium is possibly deposited from a chromium (III) complex ion such as [CrC2O4(H2O)4] + , moreover as Cr(OH)3 and Cr2O3 compounds as indicated by XPS data analysis. The role of cobalt nitrate during film formation is unclear given that cobalt was not detected within the trivalent CCC from XPS and AES data. Electrochemical LPR measurements, polarisation curves and XPS data has shown in general, self-repair corrosion protection properties for hexavalent CCC to be lacking. Instead, it is proposed that the corrosion protection behaviour for hexavalent and trivalent CCC to be barrier. Polarisation curves and LPR data showed that the corrosion resistance performance for trivalent CCC was higher than hexavalent CCC, in general. LPR data showed that the omission of cobalt nitrate and increased addition of sodium molybdate content within the Tripass LT1500 treatment solution formulation was found to overall decrease corrosion resistance within the trivalent CCC. In addition, silica based topcoat and black trivalent CCCs was also investigated and characterised using AES, SEM and LPR. Zinc whiskers was also observed from zinc electrodeposits following exposure to thermal treatment (150°C for 1 h). Elemental analysis and grain pattern investigations failed to help determine the cause of zinc whisker initiation. Zinc whiskers was seen to protrude out of hexavalent and trivalent CCCs, with the latter requiring a longer thermal exposure time.
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Winarski, David J. "Synthesis and Characterization of Transparent Conductive Zinc Oxide Thin Films by Sol-gel Spin Coating Method." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1434124579.
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Price, M. "Strip position measurement and control for consistency of zinc coating in hot-dip galvanising lines." Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638578.
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The stability of the strip between the gas knives during the wiping stage of hot-dip galvanising is critical for consistent zinc coating mass. Variation in this coating mass can result in a product that does not meet customer requirements. A significant saving can be made on the amount of zinc used and the quality of the product will be enhanced if the tolerances on the coating mass are tightened. A dynamic distributed parameter model is developed for understanding strip vibration and design of a controller for stabilisation, and is implemented in the simulation package SIMULINK. The model can be stimulated at any point by a force input and the displacement and velocity of any point can be measured. A physical model has been developed, for the purposes of validation and for test purposes, and is a scale representation of the critical part of the hot-dipping process. The computer model and physical models can be matched by use of appropriate stimulation signals and the use of genetic algorithms. The matched models show a good correlation and the confidence in the model is high. Currently air cushions and touch rolls are used to stabilise strip and the effect of these systems on the strip can be shown using both the computer and physical models. The computer model is used to develop a control scheme using the techniques of root-locus and Nichols charts. The response of the controlled system is analysed using Bode plots and step responses and shown to be an improvement on the uncontrolled system. The actuator, sensor and electronics for physical realisation of the designed control scheme are also given. The work presented here shows the method of producing a control scheme for improving the stability of strip steel within hot-dip galvanising lines.
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Wu, L. "Investigation of zinc whisker growth from electrodeposits produced using commercial electroplating baths." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/24612.
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Electroplated zinc finishes have been widely used in the packaging of electronic products for many years as a result of their excellent corrosion resistance and relatively low cost. However, the spontaneous formation of whiskers on zinc electroplated components, which are capable of resulting in electrical shorting or other damaging effects, can be highly problematic for the reliability of long life electrical and electronic equipment. To date, most research has focused on tin whiskers and much less attention has been paid to zinc whisker research. A number of mechanisms to explain zinc whisker growth have been proposed, but none of them are widely accepted and some are in conflict with each other. This study has investigated the mechanism for whisker growth from three commercial zinc electroplated coatings on mild steel substrates. Firstly, whisker growth from an alkaline cyanide-free zinc electrodeposit was studied. A reduction in deposition current density (from 50 to 5 mA/cm2) and an increase in deposit thickness (from 2 to 15 μm) both contributed to reduced whisker growth. In terms of the mechanisms of whisker growth, it was observed that the presence of spherical raised surface features (nodules) with cavities beneath, promoted whisker growth by markedly shortening the incubation time from ~ 5 months to ~ 4 weeks. More importantly, the time dependent recrystallisation of the as-deposited columnar structure is closely associated with whisker growth from both nodules and planar regions of the deposit. The formation of Fe-Zn intermetallic compounds (IMCs) was not observed at either the Fe/Zn interface or within the electroplated coatings and does not appear to be associated with Zn whisker growth. Whisker growth from an acid chloride zinc electroplated coating and a Zn-Ni alloy electroplated coating were also investigated. These two coatings were immune to whisker growth after 18 months of storage at room temperature, regardless of deposition current density, deposit thickness and substrate surface modification. Finally, the effect of potential mitigation strategies on whisker growth was evaluated. Exposure to elevated temperatures (50 to 150°C) for 24 hours promoted whisker growth by reducing the incubation time for whiskers to first appear from less than 4 weeks to less than 10 days, whilst whisker growth was significantly retarded when samples were subjected to a short period of thermal treatment (50 to 150°C) for 0.5 hour. More importantly, for a short period of thermal treatment, whisker mitigation became increasingly effective as the treatment temperature was raised. In addition, the formation of a trivalent chromium passive coating on the alkaline cyanide-free zinc electrodeposits immediately after deposition was not an effective mitigation method to retard whisker growth.
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Marsland, Wayne Edmund. "Positive release of hot-dip galvanised automotive material to prevent coating adhesion failure at customer." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678444.
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Giatti, Brandon. "Optical Properties of Nanostructured Dielectric Coatings." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1940.
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Solar cells have extrinsic losses from a variety of sources which can be minimized by optimization of the design and fabrication processes. Reflection from the front surface is one such loss mechanism and has been managed in the past with the usage of planar antireflection coatings. While effective, these coatings are each limited to a single wavelength of light and do not account for varying incident angles of the incoming light source. Three-dimensional nanostructures have shown the ability to inhibit reflection for differing wavelengths and angles of incidence. Nanocones were modeled and show a broadband, multi-angled reflectance decrease due to an effective grading of the index.
Finite element models were created to simulate incident light on a zinc oxide nanocone textured silicon substrate. Zinc oxide is advantageous for its ease of production, benign nature, and refractive index matching to the air source region and silicon substrate. Reflectance plots were computed as functions of incident angle and wavelength of light and compared with planar and quintic refractive index profile models. The quintic profile model exhibits nearly optimum reflection minimization and is thus used as a benchmark. Physical quantities, including height, width, density, and orientation were varied in order to minimize the reflectance. A quasi-random nanocone unit cell was modeled to better mimic laboratory results. The model was comprised of 10 nanocones with differing structure and simulated a larger substrate by usage of periodic boundary conditions. The simulated reflectance shows approximately a 50 percent decrease when compared with a planar model. When a seed layer is added, simulating a layer of non-textured zinc oxide, on which the nanocones are grown, the reflectance shows a fourfold decrease when compared with planar models. At angles of incidence higher than 75 degrees, the nanocone model outperformed the quintic model.
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Tu, Wei-Lun Scharf Thomas W. "Processing, structure, and tribological property interrelationships in sputtered nanocrystalline ZnO coatings." [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/ark:/67531/metadc12207.
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Narovec, David. "Analýza povrchu po řezání laserem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231983.
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This diploma thesis discusses laser cutting and the consecutive surface treatment of cut parts. The theory of laser cutting is described in the first part of this thesis, including laser history and the laser emergence principle. Cut parameters and the influence of the laser cutting on the material are described later on. The next part describes the laser cutting technological possibilities and other laser technology utilization options are outlined. In the last theory part, metal surface treatment used in the experiment is covered. Coating thickness is evaluated in the practical part of this thesis, as well as roughness, microhardness, chemical microanalysis and metalography. The evaluation of the results achieved, and optimal surface treatment execution suggestions are addressed in the last part of this thesis.
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Åslund, Johan. "Release rates and environmental impact of zinc-nickel coatings in the automotive industry." Thesis, KTH, Materials Science and Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3924.
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At present the automotive industry is due to an EU directive, replacing hexavalent chrome on vehicles. This is an extensive job as hexavalent chrome is used all over the vehicle and to large extent on fasteners (screws, nuts, rivets etc.). Chrome (VI) is used as a passivating layer on mainly zinc-iron. When replacing the hexavalent chrome with a chrome (VI) free product, the passivating properties are reduced. One of the alternatives is to replace the zinc-iron coating with a zinc-nickel coating. This coating shows great promise from the corrosion resistance point of view. Zinc-nickel is a cathodically protecting coating, and will in principle dissolve to protect the substrate from corrosion. It is therefore important to understand how, and at what rates nickel is released from zinc-nickel coatings when exposed to a chloride-rich automotive environment. The potential environmental impact of nickel needs to be evaluated before Scania can introduce this alternative as corrosion protection. Tests by Scania have previously shown that contact allergy is not an issue for zinc-nickel coatings with Cr (III) passivation.
Nickel release rates corresponding to 0,12 mg m-2yr-1 for zinc-15 % nickel coatings at a pH of 4,2 were determined from an accelerated corrosion test. Based on these values, less than 1 kg of nickel per year would be released from the Scania rolling stock if Scania were to introduce zinc-nickel coatings preferably on fasteners. This value is low compared to other sources of nickel release. In order to evaluate the toxicity of the released nickel, information about the chemical speciation, i.e. chemical forms, is needed.
Total or dissolved metal are not good predictors of ecotoxicity of metals. Chemical speciation and bioavailability must be incorporated in toxicity testing. Total or dissolved metal may be used as a worst case approximation.
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Akhtar, Anisa Shera. "Surface science studies of conversion coatings on 2024-T3 aluminum alloy." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1713.
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The research in this thesis aims to develop new mechanistic knowledge for coating processes at 2024-Al alloy surfaces, ultimately to aid the design of new protective coatings. Coatings formed by phosphating, chromating, and permanganating were characterized especially by scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy, and scanning electron microscopy . The objective was to learn about growth (nm level) as a function of time for different coating baths, as well as a function of lateral position across the different surface microstructural regions, specifically on the μm-sized Al-Cu-Mg and Al-Cu-Fe-Mn particles which are embedded in the alloy matrix . The research characterizes coating thickness, composition, and morphology.
The thesis emphasizes learning about the effect of different additives in zinc phosphating baths . It was found that the Ni²⁺ additive has two main roles : first, the rate of increase in local solution pH is limited by the slower kinetics of reactions involving Ni²⁺ compared to Zn²⁺, leading to thinner zinc phosphate (ZPO) coatings when Ni²⁺ is present. Second, most Ni²⁺ deposition occurs during the later stages of the coating process in the form of nickel phosphate and a Ni-Al oxide in the coating pores on the alloy surface, increasing the corrosion resistance. Aluminum fluoride precipitates first during the initial stages of the coating process, followed by aluminum phosphate, zinc oxide, and finally ZPO.
When Ni²⁺ is present in the coating solution at 2000 ppm, ZnO predominates in the coating above the A-Cu-Fe-Mn particle while ZPO dominates on the rest of the surface. The Mn²⁺ additive gives a more even coating distribution (compared with Ni²⁺) across the whole surface. The Mn²⁺ -containing ZPO coating is similar to the chromate coating in terms of evenness, while there is more coating deposition at the second-phase particles for permanganate coatings. The oxides on the Al-Cu-Fe-Mn and matrix regions are similar before coating, thereby confirming that a variety of observed differences in ZPO coating characteristics at these regions arise from the different electrochemical characteristics of the underlying metals. Upon exposure to a corrosive solution, the ZPO coating provides more protection to the second-phase particles compared to the matrix.
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Remešová, Michaela. "Výzkum a vývoj technologie přípravy tvrdé anodizace neželezných slitin." Doctoral thesis, Vysoké učení technické v Brně. CEITEC VUT, 2020. http://www.nusl.cz/ntk/nusl-433636.
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Práce je zaměřena na výzkum a vývoj technologie přípravy tvrdých anodických vrstev na třech různých typech neželezných materiálů a to (i) hliníkové slitině (AA1050), (ii) čistém hořčíku (99.9% Mg) a (iii) zinkové slitině (ZnTi2). Vhodnou kombinací anodizačních podmínek (napětí, proudová hustota, teplota a složení elektrolytu atd.) lze vytvářet anodické vrstvy s rozdílnými vlastnostmi. V rámci předložené práce byl prokázán vliv předúpravy a anodizačních podmínek na vzhled, morfologii, tloušťku a tvrdost vytvořených anodických vrstev. Pro zvýšení tribologických vlastností a tvrdosti byly anodické vrstvy přímo dopovány Al2O3 částicemi nebo kombinací Al2O3 a PTFE částic během anodizačního procesu. Teoretická část práce popisuje základní principy anodizace, metody používané v průmyslové praxi a v práci je také popsán technologický proces. Experimentální část je rozdělena na tři základní části. První část se věnuje anodické oxidaci hliníkové slitiny AA1050. Druhá část je zaměřena na anodizaci čistého hořčíku a poslední část je zaměřena na anodizaci zinkové slitiny ZnTi2, která není tak známá jako anodizace hliníku.
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Williams, Joseph James. "Surface reactions of zinc vapour with steel relevant to the Zn-55%Al-1.5%Si hot dip metal coating process." Faculty of Engineering, 2005. http://ro.uow.edu.au/theses/395.
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Zn-55%Al-1.5%Si coated steel strip is manufactured by the continuous hot dipping process. An important difference in the processing of Zn-55%Al-1.5%Si coated steel when compared with galvanised steel is the higher temperature of the molten alloy bath –600ºC for Zn-55%Al-1.5%Si coatings versus 450ºC for galvanised. This increase in temperature leads to an accelerated rate of evaporation of zinc into the pretreatment furnace, leading in turn to various processing difficulties. Zinc vapour in the pre-treatment furnace has long been implicated with defects known within the industry as pinholes and bare patches - uncoated areas where wetting does not occur between the strip and the molten alloy. Despite the association with zinc vapour, the exact mechanisms of pinhole and bare patch formation have not been clearly established. One possible mechanism of pinhole and bare patch formation is the direct reaction of zinc vapour with the strip surface. It has been suggested by industry experts that zinc vapour could condense on the strip, leaving a deposit that prevents wetting by molten Zn-55%Al-1.5%Si alloy. It remains that little is understood of the fundamental nature of the interaction between zinc vapour and a steel substrate. The purpose of this research was to examine the rates and mechanisms of zinc vapour condensation on clean and oxidised steel substrates. Such information is essential for understanding the reactions that occur in the metal coating line furnace. It is intended that this research will strengthen the fundamental knowledge base upon which a solution to the problem can be developed. The experimental work conducted in this study was centred on condensing zinc vapour onto substrates under specific gaseous atmospheres at atmospheric pressure. A major part of the work involved the development of a technique for depositing zinc vapour onto a steel substrate and the design and construction of an experimental apparatus. Preliminary studies were undertaken to define the design criteria for an apparatus in which the rate of condensation of zinc vapour could be measured accurately and the interaction between zinc vapour and clean and oxidised steel substrates could be examined. In this probing exercise, modifications were made to a proven design of an apparatus designed to measure evaporation rates of metals in inert gas atmospheres was used. The preliminary experiments provided a wealth of essential knowledge required to design an experimental facility in which it was possible to accurately measure the rate of condensation of zinc vapour and to study the interaction between zinc vapour and the steel substrate, as well as their potential chemical reactions. This new apparatus was specifically developed for a quantitative assessment of zinc vapour deposition, and allowed the substrate and zinc vapour to be heated in independent, but interconnecting chambers. The exposure of the substrate to the zinc vapour could be controlled with precision, and it was possible to not only measure the zinc vapour condensation rates, but also to assess the effect of using oxidising and reducing gasses during preheating of the substrate. Under conditions of high undercooling, zinc vapour deposited by the island plus continuous thin film mode, while at higher substrate temperatures, close to that expected in the industrial process, the zinc deposited more slowly, and zinc islands did not form on the substrate within the first 60 seconds of exposure. Deposition of zinc vapour on an oxidised substrate occurred at a much higher rate than on a clean steel substrate. This increase in deposition rate has been attributed to a direct reaction occurring between the zinc vapour and the iron oxide without the formation of any liquid condensate. The reaction is: Fe3O4(s) + 4Zn(v) ↔ 4ZnO(s) + 3Fe(s) This reaction will proceed to the right under sufficiently high partial pressures of zinc vapour, and at substrate temperatures both above and below the saturation temperature of the zinc vapour. It was observed that under sufficiently low partial pressures of zinc vapour, the above reaction is driven to the left. Zinc oxide has a determining influence on the wetting of the strip by the molten alloy. Immersion tests, wherein substrates deposited with zinc vapour were dipped into molten Zn-55%Al-1.5%Si alloy, were carried out to examine the effect of various zinc vapour reactions on the quality of the coatings. Deposition of zinc vapour on both clean and oxidised steel surfaces had a detrimental effect on the coating quality. In cases where zinc was deposited onto a clean steel substrate prior to immersion in the coating alloy, pinholes resulted, while zinc vapour deposition on an oxidised surface prior to immersion led to large scale uncoated areas.
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Ahmed, Omer. "Tribological and Mechanical properties of Multilayered Coatings." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501763970144729.
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Conrad, Heidi Ann. "Electrochemically Deposited Metal Alloy-silicate Nanocomposite Corrosion Resistant Materials." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271794/.
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Zinc-nickel ?-phase silicate and copper-nickel silicate corrosion resistant coatings have been prepared via electrochemical methods to improve currently available corrosion resistant materials in the oil and gas industry. A layered silicate, montmorillonite, has been incorporated into the coatings for increased corrosion protection. For the zinc nickel silicate coatings, optimal plating conditions were determined to be a working pH range of 9.3 -9.5 with a borate based electrolyte solution, resulting in more uniform deposits and better corrosion protection of the basis metal as compared to acidic conditions. Quality, strongly adhering deposits were obtained quickly with strong, even overall coverage of the metal substrate. The corrosion current of the zinc-nickel-silicate coating is Icorr = 3.33E-6 for a borate based bath as compared to a zinc-nickel bath without silicate incorporation (Icorr = 3.52E-5). Step potential and direct potential methods were examined, showing a morphological advantage to step potential deposition. The effect of borate addition was examined in relation to zinc, nickel and zinc-nickel alloy deposition. Borate was found to affect the onset of hydrogen evolution and was examined for absorption onto the electrode surface. For copper-nickel silicate coatings, optimal conditions were determined to be a citrate based electrolytic bath, with pH = 6. The solutions were stable over time and strong adhering, compact particle deposits were obtained. The corrosion current of the copper-nickel-silicate coatings is Icorr = 3.86E-6 (copper-nickel coatings without silicate, Icorr = 1.78E-4). The large decrease in the corrosion current as the silicate is incorporated into the coating demonstrates the increase in corrosion resistance of the coatings with the incorporation of silicates.
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Agbonlahor, Samson O. "Influence of pretreatment on corrosion behaviour of duplex zinc/polymer coatings on steel substrates." Thesis, Aston University, 1987. http://publications.aston.ac.uk/14288/.
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An investigation has been undertaken to determine the major factors influencing the corrosion resistance of duplex-zinc coatings on steel substrates.Premature failure of these systems has been attributed to the presence of defects such as craters and pinholes in the polymer film and debonding of the polymer film from the zinc substrate.Defects found on commercially produced samples have been carefully characterised using metallographic and scanning electron microscopy techniques. The influence of zinc substrate surface roughness, polymer film thickness and degassing of conversion coatings films on the incidence of defects has been determined.Pretreatments of the chromate, chromate-phosphate, non chromate, and alkali-oxide types were applied and the conversion coatings produced characterised with respect to their nature and composition. The effect of degassing on the properties of the films was also investigated. Electrochemical investigations were carried out to determine the effect of the presence of the eta or zeta phase as the outermost layer of the galvanized coating.Flow characteristics of polyester on zinc electroplated hot-dip continuous and batch galvanized and zinc sprayed samples were investigated using hot-stage microscopy. The effects of different pretreatments and degassing after conversion coating formation on flow characteristics were determined.Duplex coatings were subjected to the acetic acid salt spray test. The effect on adhesion was determined using an indentation debonding test and the results compared with those obtained using cross-cut/peel and pull-off tests. The locus of failure was determined using scanning electron microscopy and X-ray photoelectron spectroscopy techniques.
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GARCIA, PEDRO H. L. "Caracterizacao de uma tinta com alto teor de zinco quanto a protecao oferecida a substrato de aco carbono durante imersao em meios aquosos." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9278.
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Made available in DSpace on 2014-10-09T12:25:36Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:03:46Z (GMT). No. of bitstreams: 1 06790.pdf: 5752105 bytes, checksum: 9b66a692f462ce07b2dd97fe9220e337 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Valencia, Violeta. "Electrochemical Characterization Of Zinc-Rich Epoxy Primer-Cnt Nanocoating / Steel Interface In Co2 Saturated Under Different Flow Conditions." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1431108599.
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Van, Zandt Nicholas L. "Aqueous Fabrication of Pristine and Oxide Coated ZnSe Nanoparticles." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1623356039586297.
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Coakley, Martha. "Growth and Optical Characterization of Zinc Oxide Nanowires for Anti-reflection Coatings for Solar Cells." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/290.
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The optical properties of solar cells greatly affect their efficiencies. Decreasing the broadband and directional reflectance of solar cells increases the solar irradiance transmitted and absorbed by the cell, thereby increasing the production of electron-hole pairs. Traditional optical enhancements such as light trapping and anti-reflection coatings reduce the reflectance of silicon at an optimized wavelength and angle of incidence. They do not perform as well at high angles of incidence or over the broadband solar spectrum. Theoretical studies suggest that layers with a suitable gradient-index of refraction can create both a broadband and directional anti-reflective coating. Through their variations in height and tapered growth, Zinc oxide (ZnO) nanowires can create a gradient index anti-reflection coating. ZnO is a wide-band gap semiconductor that is non-absorbing over most of the solar spectrum. With low cost, low temperature techniques, ZnO nanowires can be grown with a variety of morphologies. ZnO nanowires were grown by aqueous chemical growth and by electrodeposition on silicon to create a gradient-index anti-reflective coating for solar cell applications. The nanowire arrays were characterized using SEM images, goniometer scattering measurements, and integrating sphere total reflectance measurements. ZnO nanowires grown by aqueous chemical growth on silicon had average diameters between 60 nm and 100 nm and average lengths between 800 nm and 1100 nm. The nanowires had vertical alignment. They exhibited relatively small diffuse reflectivities and relatively large specular reflectivities. ZnO nanowires grown by electrodeposition had greater variances in length and diameter, with average diameters between 85 nm and 180 nm and average lengths between 500 nm and 1200 nm. Electrodeposited ZnO nanowires were randomly arrayed and exhibited relatively large diffuse reflectivities and relatively small specular reflectivities. Total reflectance measurements showed that all nanowire arrays reduced the broadband reflectance of silicon. Smaller nanowire arrays outperformed the larger crystal growths. A five-fold decrease in the broadband reflectance of silicon was obtained from both vertical and randomly oriented nanowire arrays. The reflectances were constant for angles of incident below 35°. Measurements at angles of incidence greater than 35° are required to determine whether ZnO nanowires can perform as directional anti-reflective coatings and whether the morphology of the nanowires affects the directional reflectances.
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Vu, Thanh Nam. "Dissolution sélective à partir des alliages Zn-Al sur l'acier : = Selective dissolution from Zn-Al alloy coatings on steel." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00839479.
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L'objectif principal de ce travail est de comprendre les phénomènes de dissolution sélective et de cartographier la dissolution sélective des alliages Zn-Al et des alliages Zn-Mg-Al dans une moindre mesure en fonction du pH et de potentiel. Cela aidera à construire un modèle prédictif de couplage galvanique qui est une préoccupation majeure de l'industrie automobile. Pour s'approcher de la cible, nous utilisons la spectroélectrochimie d'émission atomique (AESEC) qui est une combinaison de méthodes électrochimiques et analytiques. Cette technique nous permet de quantifier en temps réel et séparément les taux de dissolution de zinc et d'aluminium à partir des alliages Zn-Al au potentiel de circuit ouvert et du potentiel appliqué dans différentes solutions. Dissolution sélective de zinc et d'aluminium à partir des alliages Zn-Al est ensuite tracée dans les gammes du pH et de potentiel. Les explications relatives à la dissolution sélective et les phénomènes d'inhibition survenant au cours d'expériences sont également donnés grâce à des résultats complémentaires de certains autres méthodes de caractérisation de surface (DRX, MEB / EDS, IR et XPS).
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Memarzadeh, Kaveh. "Investigations into the use of nano-based antimicrobial and osteoconductive coatings for bone implants." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/9001.
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Objectives: Orthopaedic and dental implants are prone to frequent infections. This can lead to detrimental and often irreversible outcomes for many patients. The objective of this study was to develop a novel system using zinc oxide nanoparticles (nZnO) as a coating material that inhibits both bacterial adhesion / growth and promotes osteoblast growth. Methods and Results: Initially bacteria (S. aureus, E. coli, S. epidermidis and P. aeruginosa) were exposed to different concentrations of zinc oxide nanoparticulate suspensions (250 μg/mL, 500 μg/mL, 1000 μg/mL and 2500 μg/mL); with the higher concentrations of the suspensions demonstrating significant bactericidal effects. A novel electrohydrodynamic atomization coating technique (EHDA) was used to deposit mixtures of nZnO and nano-hydroxyapatite (nHA) onto the surface of glass samples (1 cm2). Exposure of the coated samples to phosphate buffered saline (PBS) and adult bovine serum (ABS) and measurement of bactericidal activity demonstrated superior antimicrobial activity for 100% and 75% nZnO composite coated samples. Lactate dehydrogenase (LDH) release from osteoblast-like cells (UMR-106 and MG-63) exposed to both nano-TiO2 and nano-ZnO nanoparticulate suspension supernatants indicated minimal toxicity. Nano-ZnO coated samples did not elicit LDH release with an increase in proliferation and viability of cells was observed. Scanning electron microscopy (SEM) and optical microscopy indicated that all cell types used (mesenchymal stem cells and osteoblast-like cells) were able to maintain their normal morphological state when adhered to the surface of the nano-coated material. Further studies as regards to patterned coated samples showed an exclusive adhesion selection by osteoblast-like cells to nZnO patterned regions that needs to be further investigated. Conclusion: ZnO NPs provide an antimicrobial and biocompatible coating material for medical and dental bone implants.
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Jang, Yohan. "THE TRIBOLOGY AND FORMABILITY OF ZINC COATED STEEL SHEETS SUBJECTED TO DIFFERENT STRAIN STATES." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1270093768.
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Thesis (Master of Sciences (Engineering))--Case Western Reserve University, 2010Department of Materials Science and Engineering Title from PDF (viewed on 2010-05-25) Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Rodrigues, Joel da Silva. "Estudo da corrosão de revestimentos de zinco-ligas obtidos por imersão a quente sobre aços baixo-carbono." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/49059.
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O zinco vem sendo utilizado, já há bastante tempo, como revestimento protetor e decorativo para peças metálicas [1]. No entanto, cada vez mais a indústria busca revestimentos protetores que sejam mais resistentes à corrosão, que tenham boas características de soldabilidade, pintabilidade e, principalmente baixo custo. Os métodos mais comuns pelos quais os revestimentos de zinco são aplicados são imersão a quente, eletrodeposição e aspersão térmica. O presente trabalho tem como objetivo caracterizar a morfologia dos revestimentos Galvanized (GI), Galvannealed (GA) e Zn-55Al de zinco obtidos pelo processo de imersão a quente, verificar o comportamento eletroquímico e analisar o comportamento corrosivo dos revestimentos pelas técnicas de Potenciometria e Eletrodo Vibratório (SVET). Os resultados demonstraram que é possível a análise das fases por voltametria em microcélula no revestimento em que as fases foram crescidas, porém, não é possível aplicar a técnica nas diferentes fases formadas nos revestimentos industriais devido à espessura dos revestimentos. Não foi observado influência da luz Ultravioleta-visível na taxa de corrosão dos revestimentos estudados por SVET e esta técnica mostrou-se satisfatória para grandes aumentos e pequenas áreas. As análises por SVET demonstraram a possibilidade de analisar a corrosão localizada em diferentes fases intermetálicas nos revestimentos.Zinc has been used for quite some time, as decorative and protective coating for metal parts. However, the industry increasingly seeks protective coatings that are more resistant to corrosion, have good weldability characteristics, and especially low cost. The most common methods by which zinc coatings are applied are hot dipping, electroplating and thermal spraying. The present work aims to characterize the morphology of the coatings Galvanized (GI), galvannealed (GA) and Zn-55Al of zinc obtained by hot dip process, check the electrochemical behavior and analyze the behavior of coatings for corrosion techniques of pots and Vibrating electrode (SVET). The results showed that it is possible to analyze the phases by microcell voltammetry in the coating in which the phases were grown, however, is not possible to apply the technique in the different phases formed in industrial coatings due to the thickness of coatings. There was no influence of UV-VIS in the corrosion rate of the coatings studied by SVET and this technique was satisfactory for large and small areas increases. The analysis by SVET demonstrated the possibility of analyzing the localized corrosion in different intermetalic phases in coatings.
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Vallien, Ante. "Material characterization of multi-layered Zn-alloy coatings on fasteners : Effects on corrosion resistance, electrical conductivity and friction." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240956.
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Electroplated zinc-alloy coatings have been used on fasteners in the automotive industry for many years. The coating often consists of three layers: a zinc-alloy layer, a passivation layer and a sealer or top-coat. The coating layers affect the functional properties of the fastener (mainly the corrosion resistance, friction coefficient and electrical conductivity), and the aim of this thesis has been to increase the understanding of how these functional properties are affected by the properties of the coating. The corrosion resistance, friction coefficient and electrical conductivity of several different fasteners have been tested. Variations in these properties are connected with morphological and chemical properties of the electro-deposited zinc-alloy coating, passivation layer and sealer/top-coat of the fasteners. Measurement methods include scanning electron microscope and energy dispersive x-ray spectroscopy (SEM-EDX), light optical microscope (LOM), x-ray fluorescence (XRF), glow discharge optical emission spectroscopy (GD-OES), broad ion beam (BIB) and Fourier transform infrared spectroscopy (FTIR). From the results it can be concluded that the surface structure of zinc-nickel layers differs significantly from supplier to supplier. Screws with a thicker and rougher zinc-nickel surface structure displays higher friction values, but lower electrical resistance values. Optimisation of both of these properties is thus challenging. The distribution and surface structure of the outmost top-coat layer also differs between suppliers, but no connection between this and the functional properties of the screw has been found. The corners of the screw heads are often lacking a proper zinc-alloy coating, and this is also where corrosion is initiated. In general, the zinc-nickel alloy coating systems are performing better and display less corrosion spreading effects than the zinc-iron or pure zinc systems in terms of corrosion.Elektropläterade zinklegeringsbeläggningar har använts på fästelement inom bilindustrin under många år. Beläggningen består ofta av tre skikt: ett zinklegeringsskikt, ett passiveringsskikt och en ”top-coat”, eller ”sealer”. Beläggningsskikten påverkar fästelementens funktionella egenskaper (främst korrosionsbeständighet, friktionskoefficient och elektrisk ledningsförmåga) och syftet med denna avhandling har varit att öka förståelsen för hur dessa funktionella egenskaper påverkas av ytbeläggningens egenskaper. Korrosionsmotståndet, friktionskoefficienten och den elektriska ledningsförmågan hos flera olika fästelement har mätts. Variationer i dessa egenskaper kopplas till de morfologiska och kemiska egenskaperna hos den elektropläterade zinklegeringsskiktet, passiveringsskiktet och top-coat-skiktet hos fästelementen. Mätmetoder inkluderar svepelektronmikroskop och röntgenspektroskopi (SEMEDX), ljusoptiskt mikroskop (LOM), röntgenfluorescens (XRF), optisk strålningsspektroskopi (GD-OES), bred jonstråle (BIB) och Fourier-transformerad infraröd spektroskopi (FTIR). Av resultaten kan man dra slutsatsen att ytstrukturen hos zink-nickelskiktet skiljer sig avsevärt från leverantör till leverantör. Skruvar med tjockare och hårdare zink-nickelytstruktur visar högre friktionsvärden, men lägre elektriska resistansvärden. Optimering av båda dessa egenskaper är således utmanande. Distributionen och ytstrukturen hos det yttersta top-coat-skiktet skiljer sig också mellan leverantörer, men ingen samband mellan detta och skruvens funktionella egenskaper har hittats. Skruvhuvudets hörn saknar ofta en lämplig zinklegeringsbeläggning, och det är också där korrosion initieras. I allmänhet fungerar zink-nickellegeringsbeläggningssystemen bättre och visar mindre spridningseffekter i termer av korrosion än zinkjärn eller rena zinksystem.
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Claudel, Florian. "Development of anticorrosive Zn-based alloy coatings for cold formed steel body parts." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0264.
Full textAbstract:
De nombreux revêtements sont utilisés par les constructeurs automobiles pour la protection contre la corrosion de pièces de carrosserie embouties à froid. D’après la littérature, diverses solutions et approches ont été suggérées au cours des dernières décennies. Cependant, seulement quelques systèmes ont pu aboutir à une production en série. L’objectif de la thèse de doctorat présentée ici est de développer et caractériser de nouveaux revêtements anticorrosifs à base d’alliages de zinc pour la protection contre la corrosion de composants en acier mis en forme à froid. Sur la base d’une revue de la littérature détaillée, deux approches d’intérêt ont été considérées, consistant en l’électrodéposition impulsionnelle de dépôts de ZnMn et de ZnMn-Al2O3. Les revêtements ont été caractérisés en termes de composition chimique, microstructure et cristallographie. L’aptitude des revêtements à une application dans l’industrie a été évaluée sur la base du comportement en corrosion, de la formabilité à froid et l’aptitude aux opérations de peintures. L’utilisation de l’électrodéposition impulsionnelle a permis d’obtenir des revêtements de ZnMn monophasés, absent de porosités et compacts, présentant une teneur en Mn avoisinant les 15 m.% avec un fort rendement. L’électrodéposition sur des substrats variés a révélé un procédé de déposition stable et reproductible. Des mesures électrochimiques et des tests de corrosion accélérés ont révélé une performance anticorrosive des alliages de ZnMn intéressante. Une amélioration du temps d’apparition de la rouille rouge et qu’une diminution de la vitesse de corrosion ont été observées en comparaison avec les revêtements traditionnels. Des analyses de la mise en forme à froid ont montré un comportement prometteur des dépôts de ZnMn. Des premiers tests de phosphatation et peinture ont démontré la bonne aptitude des revêtements pour ces procédés. Cependant, certaines limitations ont été identifiées avec notamment des propriétés insatisfaisantes des revêtements lors d’une immersion en milieu chloré. De plus, des porosités ont pu être observées à proximité de l’interface entre le dépôt et le substrat. Dans le but de résoudre ces problèmes, l’électrodéposition de revêtements composites ZnMn-Al2O3 a été considérée. L’impact des particules et des paramètres électriques sur la distribution des particules dans la matrice métallique a été étudié. Avec des paramètres optimisés, des dépôts composites homogènes, compacts et monophasiques contenant jusqu’à 15 m.% de Mn ont pu être obtenus avec de forts rendements. Des analyses poussées ont aussi révélé la présence de particules sur la surface ainsi qu’à l’interface substrat - film. Des premiers essais mécaniques ont montré une augmentation de la dureté des dépôts composites. Des mesures électrochimiques ont également donné un aperçu très prometteur sur le comportement anticorrosif des revêtements ZnMn-Al2O3Numerous coating systems are used by the automotive manufacturers for the corrosion protection of cold formed steel body parts. According to the literature, various approaches and solutions were suggested over the past decades. However, only a few systems were able to go into serial production. The objective of the present doctorate thesis is to develop and characterize alternative anticorrosive coatings based on Zn-alloys for the corrosion protection of cold formed steel components used for automotive body parts. Based on a thorough literature review, two interesting approaches were considered, consisting in the pulse electrodeposition of Zn-Mn and ZnMn-Al2O3 coatings. The deposits were characterized in order to determine their composition, microstructure as well as their crystallographic properties. The suitability of these new deposits was then assessed based on their anticorrosive behaviour, cold formability and paintability. Using pulse electrodeposition permitted to deposit monophasic, pore-free and compact Zn-Mn alloys containing about 15 wt.% Mn at high current efficiencies. Electrodeposition on various substrates exposed a stable and reproducible deposition process. Electrochemical experiments and accelerated corrosion tests revealed a promising anticorrosive performance of the Zn-Mn alloys. A substantial improvement in the time before red rust appearance and a significant decrease of the corrosion rate were observed in comparison to the traditional Zn deposits. While a slight increase of the hardness was observed in comparison to the Zn coatings, a lower crack density was observed on the Zn-Mn deposits after tensile experiments. Preliminary phosphating and painting tests revealed the good suitability of the Zn-Mn alloys for those processes with the formation of a dense and homogeneous phosphate crystals network and the successful deposition of a homogeneous and pore-free electrophoretic paint layer. However, some challenges were identified with Zn-Mn deposits presenting some unsatisfactory properties when immersed in chloride-containing environments. With the aim to solve these issues, the deposition of ZnMn-Al2O3 composite coatings was considered. The impact of the particles and electric parameters were investigated with a particular attention given to the distribution of the particles in the metallic matrix. Using optimized deposition parameters, homogeneous, compact and monophasic composite coatings containing about 15 wt.% Mn were obtained at high efficiencies. Further analyses revealed the presence of particles on the surface as well as at the substrate – deposit interface. First mechanical tests revealed interesting properties of the composite coatings with a substantial increase of the coating hardness. Electrochemical experiments also revealed some promising insights on the corrosion behaviour of the ZnMn-Al2O3 deposits
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Vimalanandan, Ashokanand [Verfasser], Michael [Akademischer Betreuer] Rohwerder, and Martin [Akademischer Betreuer] Muhler. "Investigation of redox-responsive coatings for zinc corrosion protection / Ashokanand Vimalanandan. Gutachter: Michael Rohwerder ; Martin Muhler." Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1095884336/34.
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