The aim of the research in this thesis was to study how environmentally friendly corrosion inhibitors for cooling water systems might be developed and used. Firstly, reduced toxicity inorganic corrosion inhibitors (i.e. nitrite/molybdate) were considered. Secondly, non-toxic inhibitors based on mono and di-basic salts of carboxylic acids were studied systematically as a function of carbon chain length. For nitrite inhibitor alone, a concentration of 7 mM NaNO2 was effective to inhibit carbon steel in chloride media of 10 mM NaCl, while 10 mM nitrite was needed in sulphate media of 3.66 mM Na2SO4. However, it was found possible to significantly reduce the concentration of nitrite by adding molybdate in synergy. This was attributed to the nitrite passivation combined with ferrous molybdate salt film pore plugging thus promoting a continuous and protective film on the material within these media. Thus, in pH 6-10 an inhibition efficiency of 97% was recorded with a mixture of 3 mM nitrite/2 mM molybdate in both chloride and sulphate media and at 25°C and 60°C. However as the solution pH decreased below pH 4 the inhibition efficiency decreased to about 47%.In the second part of the study, the use of sodium salts of carboxylic acids with different chain lengths has been investigated. In this part a summary of the performances and limitations of both mono- and di-sodium carboxylate inhibitors are presented. For mono-carboxylates, the inhibition efficiency reached a maximum value of 95% in stagnant aerated solutions at a chain length of C=4 with a critical inhibition concentration of 6 mM in 10 mM NaCl solution. However the inhibition efficiency gradually decreased as the number of carbon atoms in the chain length increased to more than 8, or less than 4, and this was in agreement with surface hydrophobicity and contact angle results. For lower chain lengths, the carboxylate anion becomes more acidic and complexing of the metal ion while for longer chain lengths, the carboxylate anion becomes less soluble and tends to micellise wherby the active groups are no longer available for surface adsorption. For di-carboxylates the inhibition efficiency improved in 10 mM NaCl at a given chain length compared with mono-carboxylates, and continued to increase to C=8 (sebacate), which achieved excellent inhibition efficiency. However, sebacate is costly so a blend with ethyl hexanoate was found to be economically favoured.

A eficiência de antocianinas como inibidores de corrosão da liga de alumínio 2024-T3 foi avaliada através de medidas eletroquímicas como a espectroscopia de impedância eletroquímica e polarizações anódica e catódica. Soluções de NaCl 0,025 mol.L-1 contendo diferentes concentrações (800, 1000, 2000, 3000, 5000 e 7200 ppm) de antocianinas extraídas da uva foram preparadas para analisar o efeito da presença destas substâncias quando em contato com a liga de alumínio 2024-T3. Medidas de espectroscopia de impedância eletroquímica apresentaram uma diminuição sobre a dispersão dos pontos nas regiões de baixas frequências com o acréscimo do tempo de contato das antocianinas com a superfície da liga de alumínio 2024-T3 de 1 hora para 3 dias de imersão. Além disso, o comportamento indutivo nestas regiões decresceu após 3 dias de imersão com uma elevação considerável da resistência à polarização e da eficiência de inibição em 1000 ppm de antocianinas. Sob polarizações anódica e catódica, também foi verificado um melhoramento generalizado das propriedades anticorrosivas como potencial de corrosão, corrente de corrosão e eficiência de proteção contra a corrosão, para a concentração de 1000 ppm de antocianinas. Análises de microscopia eletrônica de varredura, microscopia de força atômica e espectroscopia por dispersão de energia, confirmam a adsorção de antocianinas na superfície da liga, assim como medidas de absorbância após 3 dias de imersão. / The efficiency of anthocyanins as corrosion inhibitor of the 2024-T3 aluminum alloy was evaluated by electrochemical measurements such as electrochemical impedance spectroscopy and anodic and cathodic polarizations. NaCl solutions 0.025 mol.L-1 containing different concentrations (800, 1000, 2000, 3000, 5000 and 7200 ppm) of anthocyanins extracted from grape were prepared to examine the effect of the presence of these substances when in contact with the 2024-T3 aluminum alloy. Electrochemical impedance spectroscopy measurements showed a decrease on the dispersion of points in the lower frequency regions with an increase of contact time of anthocyanins with the surface of the 2024-T3 aluminum alloy from 1 hour to 3 days of immersion. In addition, the inductive behavior in these regions decreased after 3 days of immersion with a considerable increase of the polarization resistance and inhibition efficiency of 1000 ppm of anthocyanins. Under cathodic and anodic polarizations, it was noted a general improvement in the anticorrosive properties such as corrosion potential, corrosion current and efficiency of protection against corrosion for the concentration of 1000 ppm of anthocyanins. Analyses of scanning electron microscopy, atomic force microscopy and energy dispersive spectroscopy confirm anthocyanins adsorption on to the surface alloy, as well as absorbance measurements in a spectrophotometer after 3 days of immersion.

A eficiência de antocianinas como inibidores de corrosão da liga de alumínio 2024-T3 foi avaliada através de medidas eletroquímicas como a espectroscopia de impedância eletroquímica e polarizações anódica e catódica. Soluções de NaCl 0,025 mol.L-1 contendo diferentes concentrações (800, 1000, 2000, 3000, 5000 e 7200 ppm) de antocianinas extraídas da uva foram preparadas para analisar o efeito da presença destas substâncias quando em contato com a liga de alumínio 2024-T3. Medidas de espectroscopia de impedância eletroquímica apresentaram uma diminuição sobre a dispersão dos pontos nas regiões de baixas frequências com o acréscimo do tempo de contato das antocianinas com a superfície da liga de alumínio 2024-T3 de 1 hora para 3 dias de imersão. Além disso, o comportamento indutivo nestas regiões decresceu após 3 dias de imersão com uma elevação considerável da resistência à polarização e da eficiência de inibição em 1000 ppm de antocianinas. Sob polarizações anódica e catódica, também foi verificado um melhoramento generalizado das propriedades anticorrosivas como potencial de corrosão, corrente de corrosão e eficiência de proteção contra a corrosão, para a concentração de 1000 ppm de antocianinas. Análises de microscopia eletrônica de varredura, microscopia de força atômica e espectroscopia por dispersão de energia, confirmam a adsorção de antocianinas na superfície da liga, assim como medidas de absorbância após 3 dias de imersão. / The efficiency of anthocyanins as corrosion inhibitor of the 2024-T3 aluminum alloy was evaluated by electrochemical measurements such as electrochemical impedance spectroscopy and anodic and cathodic polarizations. NaCl solutions 0.025 mol.L-1 containing different concentrations (800, 1000, 2000, 3000, 5000 and 7200 ppm) of anthocyanins extracted from grape were prepared to examine the effect of the presence of these substances when in contact with the 2024-T3 aluminum alloy. Electrochemical impedance spectroscopy measurements showed a decrease on the dispersion of points in the lower frequency regions with an increase of contact time of anthocyanins with the surface of the 2024-T3 aluminum alloy from 1 hour to 3 days of immersion. In addition, the inductive behavior in these regions decreased after 3 days of immersion with a considerable increase of the polarization resistance and inhibition efficiency of 1000 ppm of anthocyanins. Under cathodic and anodic polarizations, it was noted a general improvement in the anticorrosive properties such as corrosion potential, corrosion current and efficiency of protection against corrosion for the concentration of 1000 ppm of anthocyanins. Analyses of scanning electron microscopy, atomic force microscopy and energy dispersive spectroscopy confirm anthocyanins adsorption on to the surface alloy, as well as absorbance measurements in a spectrophotometer after 3 days of immersion.

No description available.

No description available.

Superhydrophobic and lubricant-infused porous surfaces are two classes of non-wetting surfaces that are inspired by the adaptation of natural surfaces such as lotus leaves, pond skater legs, butterfly wings, and Nepenthes pitcher plant. This dissertation focuses on fabrication and in depth study of bioinspired functional metallic surfaces for applications such as power plant condensers and marine applications. Toward that, first, facile and scalable methods are developed for the fabrication of superhydrophobic surfaces (SHS) and lubricant-infused surfaces (LIS). Second, the corrosion inhibition mechanism of SHS was systematically studied and modeled via electrochemical methods to elucidate the role of superhydrophobicity and other parameters on corrosion inhibition. The anti-corrosion properties of SHS and LIS were systematically studied over a range of temperatures (23°C–90°C) to simulate an actual condenser environment. Moreover, the environment of application often involves using harsh cleaning chemicals. The fabricated non-wetting surfaces were examined over a wide range of acidity and basicity (pH=1 to pH=14). Third, the durability of SHS and LIS is systematically assessed using a set of testing protocols including water impingement tests, scratch wear tests, and accelerated chemical corrosion tests. Considering that industrial environments of application are often turbulent, in addition to static long term corrosion tests, long term dynamic durability was studied in a simulated turbulent condition. Fourth, the performance of the fabricated nonwetting surfaces was systematically studied against calcium sulfate scaling in turbulent conditions and different temperatures. An analytical relationship based on the Hill-Langmuir model is proposed for the prediction of fouling on nonwetting and conventional surfaces alike in dynamic conditions. Overall 1048 individual samples were studied via over 3000 measurements in this dissertation to establish a comprehensive fundamental knowledge base on fabrication and anti fouling characteristics of metallic nonwetting surfaces, which profoundly helps to design appropriate surfaces and fabrication methods based on the use environment. / Doctor of Philosophy / Metallic surfaces such as copper, brass, and aluminum are everywhere in our daily lives. From tumblers, household pipes to the bank of tubes in power plants condensers. Fouling of these surfaces has significant performance and economic impact. Scaling is a type of crystallization fouling like the familiar limescale everyone is familiar to see around the surface of a house kettle. Corrosion is another type of fouling and is detrimental to metallic surfaces. For example, 50% of water consumption in the U.S. is being used in thermo-electric power plants where fouling of metallic surfaces will impede the flow of working fluid, therefore increasing power needed for pumping, decrease efficiency, and decrease ultimate lifetime. One study in 2019 shows corrosion costs 3% of the gross national products of China and it is already known to be similar for other major economies like the USA, which is a hefty cost. Nature has inspired a lot of solutions for mankind. In this work, inspired by natural surfaces such as lotus leaves, butterfly wings, and pond skater legs, a class of superhydrophobic surfaces (SHS) was fabricated. Moreover, a closer look at how the complex human body puts everything in order exposes one of its most striking and essential characteristics: how wet and lubricated its interfaces are. Our lungs, eyes, joints, intestine, bones; either hairy or porous, all are lined wet surfaces that work as fouling inhibitors and defect free surfaces. This also have been observed elsewhere such as on Nepenthes pitcher plant. Inspired by these, another class of non-wetting surfaces, lubricant-infused surfaces (LIS) was fabricated. This dissertation for the first time investigates a rational methodology in the fabrication of metallic SHS and LIS and their anti-scaling and anti-corrosion properties in different environments of application, including a range of temperature (23°Câ€"90°C), various solutions (pH=1 to pH=14), and long-term static and dynamic (turbulent condition) durability. It is believed that this work would profoundly help to identify appropriate nonwetting metallic surfaces based on the intended use environment.

No description available.

No description available.

It is known that organic monolayers on solid surfaces can enable electronic properties that are absent in the bulk of the solid materials. Often, once the organic film come into the contact with a solid surface, the established electronic interaction at their interface remains undisturbed. However, using a redox-active organic monolayer creates the possibility for modulating the extent and the direction of the interfacial charge transfer, establishing a switch at the interface. The theme of this thesis is investigation of the interfacial interaction of different redox states of a molecular switch, phenyl-capped aniline tetramer (PCAT) with iron oxide and graphite surfaces and their potential application in electronic devices. The nucleation and growth of submonolayer films of different oxidation states of PCAT on iron oxide surface was studied. Using atomic force microscopy and scaling island size distribution method the surface diffusion parameters of these islands were evaluated. Using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy the changes in these organic monolayers before and after interaction with iron oxide were demonstrated. However, these techniques were unable to provide similar data from the solid surface side of the interface. Instead, we were able to demonstrate the changes in the iron oxide film as a result of interfacial charge transfer using electrical conductivity measurement techniques. Based on this information a microfluidic chemical sensor based on the interface of pencil film and PCAT for quantification of free chlorine in drinking water was constructed. Using XPS and UV-vis spectroscopy it was shown that the interaction the organic monolayer with sodium hypochlorite solution leads to the development of positive charges on the backbone of PCAT. This electrostatic charge can affect the charge transport in the pencil film causing the modulation of electrical conductivity of the film. The presented work demonstrates alternative pathways for the design of novel hybrid electronic devices based on thin molecular film and solid surfaces. / Thesis / Doctor of Philosophy (PhD)

With the advancement and accessibility of local probing techniques that can operate at the submicron scale it has become possible to analyse the local corrosion properties of industrially important metallic materials and relate these properties to microstructure characteristics of the same materials. In this doctoral study the focus has been on copper-zinc samples, both as industrial brass alloys and as micro-patterned copper-zinc samples. They have been exposed to dilute chloride solutions and to an atmosphere that mimics indoor conditions that cause corrosion. The main goal has been to investigate micro-galvanic effects caused by surface heterogeneities in the copper-zinc samples, and the corrosion inhibition ability of a self-assembled octadecanethiol (ODT, CH3(CH2)17SH) monolayer when applied to these heterogeneous samples. The local chemistry, local electrochemistry, and local surface chemistry in the presence of the copper-zinc galvanic couplings have been elucidated, and their importance has been investigated for corrosion initiation, propagation, termination, and inhibition. A broad spectrum of local probe techniques has been utilised. They include optical microscopy (ex situ and in situ), electrochemical techniques, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, scanning Kelvin probe force microscopy and confocal Raman spectroscopy. In addition, infrared reflection absorption spectroscopy (in situ) and vibrational sum frequency spectroscopy have been employed to analyse the formation of corrosion products and monitor the corrosion kinetics.    A characteristic selective zinc dissolution process was triggered in non-metallic inclusions when a brass alloy was exposed to 1 mM NaCl. Disc-like corrosion areas spread radially outwards from the inclusions, the shape and termination of which was attributed to accessibility to chloride ions. An ODT-layer deposited on brass retarded access to chloride ions at the brass surface and slowed down the radial corrosion process. Instead a delayed formation of filiform-like corrosion was observed.    Upon exposure of the copper-zinc patterned sample to humidified air containing formic acid, micro-galvanic effects were induced by the copper patches on zinc that accelerated the zinc dissolution in the thin aqueous adlayer with concomitant precipitation of zinc formate. The micro-galvanic effects not only resulted in accelerated corrosion rates for zinc, but also in broadening of shapes and atomic structures for the corrosion products formed. Crystalline zinc oxide and zinc formate were observed on the copper-zinc patterned samples, whereas amorphous zinc oxide and zinc formate were formed on the bare zinc surface. Micro-galvanic effects occurred in the two-phase Cu40Zn (Cu with 40 wt% Zn) brass alloy as well, induced by more zinc-rich beta-phase grains surrounded by an alpha matrix with lower zinc-content.    The application of a self-assembled monolayer of ODT for corrosion inhibition of pure zinc and the patterned copper-zinc samples was also explored. In situ infrared reflection absorption spectroscopy analyses showed that ODT initially reduced the rate of zinc formate formation on pure zinc and on the copper-zinc micro-patterned sample. However, the inhibition efficiency was slightly reduced with exposure time due to local removal of ODT on pure zinc and on the micro-patterned samples. This caused micro-galvanic effects that resulted in increased rates of zinc formate formation on the ODT-covered samples – even higher than on the uncovered samples. When applied to the single-phase Cu20Zn alloy, ODT resulted in a corrosion inhibition that was comparable to that of pure copper, a metal for which ODT has shown very good corrosion inhibition. On double-phase Cu40Zn local galvanic effects resulted in less efficient corrosion inhibition and more abundant corrosion products than on Cu20Zn. Based on vibrational sum frequency spectroscopy, the ODT-layer retained its well-ordered molecular structure throughout the exposure to both Cu20Zn and Cu40Zn.    In all, the inhibiting action of the ODT-layer was attributed to the transport hindrance of corrosion promoters (O2, H2O, and HCOOH) to the brass surface. This result suggests that ODT can function as a temporary corrosion inhibitor for brass exposed to benign indoor environments. / Med utvecklingen av och tillgången till lokala analysmetoder som kan ge information med en lateral upplösning på mindre än en mikrometer har det blivit möjligt att analysera lokala korrosionsegenskaper hos industriellt viktiga metalliska material och relatera dessa egenskaper till mikrostrukturen hos samma material. I doktorsavhandlingen har denna möjlighet utnyttjats för koppar-zinkprover, dels som industriella mässingslegeringar dels som mikro-mönstrade koppar-zinkprover, som exponerats för utspädda kloridlösningar samt för en atmosfär som kan efterlikna den atmosfäriska korrosionen inomhus. Det huvudsakliga målet har varit att undersöka dels mikro-galvaniska korrosionseffekter som orsakas av heterogeniteter på koppar-zinkytorna dels korrosionsförmågan hos självorganiserande monolager av oktadekantiol (ODT, CH3(CH2)17SH) vid adsorption på dessa heterogena ytor. På så vis har den lokala kemin, ytkemin och elektrokemin kunnat klarläggas i närvaro av galvaniska effekter, och dess betydelse har undersökts för korrosionsprocessens initiering, propagering, terminering och inhibering. Ett brett spektrum av lokala analysmetoder har utnyttjats. De innefattar ljusoptisk mikroskopi (ex situ och in situ), elektrokemiska metoder, svepelektronmikroskopi med energidispersiv röntgen-spektroskopi, atomkraftsmikroskopi för mikro-kartering och Voltapotentialmätningar samt konfokal Raman-spektroskopi. Dessutom har infrarödreflektions absorptionsspektroskopi (in situ) och vibrationssummafrekvens spektroskopi (engelska: vibrational sum frequency generation) använts.    När en mässingslegering exponerades för 1 mM NaCl observerades en selektiv utlösning av zink med karakteristiskt utseende som växte radiellt från icke-metalliska inneslutningar för att bilda cirkulärt formade korrosionsområden. Formen och termineringen av denna korrosionsprocess bestäms av tillgången på kloridjoner. När ett monolager av ODT adsorberades på mässingslegeringen hämmades tillgången av kloridjoner på mässingsytan och den radiella korrosionsprocessen stannade upp. Istället iakttogs en fördröjd bildning av s.k. filiform korrosion.    Vid exponering av mikro-mönstrade koppar-zinkprover för befuktad luft med låga tillsatser av myrsyra inducerades mikro-galvaniska effekter i gränsen mellan koppar och zink som accelererade utlösningen av zink i den adsorberade fuktfilmen på provet, under samtidig utfällning av zinkformat. De mikro-galvaniska effekterna resulterade inte bara i förhöjda korrosionshastigheter jämfört med de på ren zink, utan även i andra faser hos bildade korrosionsprodukter. På de mikro-mönstrade koppar-zinkproverna bildades kristallint zinkoxid och zinkformat, under det att amorft zinkoxid och zinkhydroxyformat bildades på ren zink. Mikrogalvaniska effekter observerades även i den tvåfasiga mässingslegeringen Cu40Zn (Cu med 40 vikt-% Zn) orsakade av kontakten mellan den mer zinkrika beta-fasen och den omgivande alfa-fasen med lägre zinkhalt.    Appliceringen av ett självorganiserat monolager av ODT för korrosionsinhibering av ren zink och koppar-zinkprover har också undersöks. In situ infrarödreflektions absorptionsspektroskopi visade att adsorberat ODT initialt hämmade bildningen av zinkformat på ren zink och på de mikro-mönstrade koppar-zinkproverna. Med tiden minskade ODTs korrosionsinhiberings-förmåga på grund av att ODTs vidhäftning lokalt försvann. De mikro-galvaniska effekter som därigenom uppstod resulterade i bildandet av zinkformat som med tiden blev snabbare på de ODT-belagda proverna än på motsvarande prover utan ODT. När ODT applicerades på den enfasiga mässingslegeringen Cu20Zn resulterade detta i en korrosionsinhibering som var jämförbar med den på ren koppar, en metall på vilken ODT tidigare visat mycket bra korrosionsskydd. På den tvåfasiga mässingslegeringen Cu40Zn ledde lokala galvaniska effekter till en mindre effektiv korrosions-inhibering och en rikligare mängd korrosionsprodukter än på Cu20Zn. Baserat på vibrationssummafrekvens spektroskopi behöll ODT-lagret dess välordnade struktur under hela exponeringen på både Cu20Zn och Cu40Zn.    ODTs korrosionsinhibering tillskrivs främst transport-hämningen av korrosionsstimulatorer (O2, H2O och HCOOH) till mässingsytan och antyder att ODT kan fungera som en temporär korrosionsinhibitor för mässing i milda inomhusmiljöer. / <p>QC 20140915</p>