Master of Science (MS), Ohio University, 2005, Chemical Engineering (Engineering)

The present study has been conducted to find the corrosion mechanisms and rates of an AISI 1018 steel in the presence of CO 2 and trace amounts of H 2 S using classical electrochemical techniques. The results obtained from experiments using electrochemical impedance spectroscopy measurements were theoretically analyzed by a semi-mechanistic model to reveal the conditions on the surface of the specimen used in the experiment. The experiments were designed to see the effect of different saturation values of iron carbonate and iron sulfide in the bulk solution on the corrosion rate of the sample. The experiments were conducted in a large scale (1000 lit) hastelloy flow loop at a fixed temperature of 60°C and total pressure of 7.9 bar. All experimental conditions were monitored regularly for the duration of the experiment. It was observed that the presence of trace amounts of H 2 S in the system decreased the corrosion rate significantly over time under the specific experimental conditions studied. This was due to the formation of an iron carbonate scale or iron sulfide scale, or both, which acted as a barrier to the diffusion of the corrosive species to the surface of the metal, thus decreasing corrosion rate.

Committee: Srdjan Nesic (Advisor) Subjects:

Doctor of Philosophy (Ph.D.), University of Dayton, 2023, Engineering

Given a set of video imagery from unknown device provenance, video-based source camera identification (V-SCI) refers to a task of identifying which device collected the imagery. V-SCI techniques predominantly leverage photo response non-uniformity (PRNU) patterns extracted from digital video for device identification decisions. PRNU patterns function as device fingerprints and SCI methods using PRNU from digital still imagery (I-SCI) are relatively mature; however, advancements in video processing, namely electronic image stabilization (EIS) algorithms, degrade video extracted PRNU distinctiveness yielding a significant obstacle toward extending I-SCI performance to EIS processed video datasets. We provide a new, more relevant PRNU dataset, UDAYTON23VSCI, for V-SCI benchmarking in contrast to current publicly available datasets. To address the EIS V-SCI challenge, we present a data-driven approach to exploit PRNU signals derived from EIS video via ``device-specific'' neural networks implemented with a novel PRNU image training and transfer learning strategy. Results implementing our device-specific network approach on UDAYTON23VSCI and a leading publicly available dataset confirm the advantages of our approach over state of the art SCI methods. We provide a new PRNU computation approach via Log-noise PRNU estimation which overcomes multiplicative noise constraints inherent to PRNU patterns in imagery. We show our Log-noise PRNU estimation approach outperforms the current widely accepted PRNU estimation approach based on maximum likelihood estimation (MLE) in V-SCI task thus eliminating the need for MLE in computing PRNU. Lastly, by removing MLE PRNU computation requirement, we show our Log-noise PRNU estimation approach is a key contribution toward realizing a fully data driven end-to-end (E2E) network design for tackling EIS V-SCI.

Committee: Keigo Hirakawa (Advisor); Barath Narayanan (Committee Member); Partha Banerjee (Committee Member); Vijayan Asari (Committee Member) Subjects: Artificial Intelligence; Electrical Engineering

Master of Science, Miami University, 2022, Chemical, Paper and Biomedical Engineering

Polyurethane coatings are widely used to prevent corrosion. TiO2/Polyurethane composite coatings with 1 – 5 wt% TiO2 compositions were produced, and the barrier properties were assessed. Techniques including the accelerated cyclic electrochemical technique (ACET), water contact angle measurements, scanning electron microscopy (SEM), and pull-off adhesion testing were employed to characterize the coating barrier properties. The results showed that the addition of TiO2 to polyurethane coatings in the amount of 1 – 3 wt% improved barrier properties - corrosion resistance, water contact angle, and pull-off adhesion - compared to polyurethane alone. Of these composites, the 3 wt% was the optimal TiO2 composite to achieve the best barrier properties. Conversely, the 4 wt% and 5 wt% composites were found to provide minimal improvement in water contact angle and pull-off adhesion as well as reduced performance in corrosion resistance compared to polyurethane alone. The reduced performance of the 4 wt% and 5 wt% composite coatings was attributed to coating cracking and particle agglomeration caused by the overabundance of TiO2 within the coating.

Committee: Lei Kerr (Advisor); Shashi Lalvani (Advisor); Giancarlo Corti (Committee Member) Subjects: Chemical Engineering; Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 2021, Materials Science and Engineering

Alloying additions are employed in magnesium (Mg) to increase its corrosion performance, formability, and strength. Widely used commercial alloys such as the AZ series use Aluminum (Al) and Zinc (Zn) as the main alloying elements. The alloys used in this research contained 3, 6, or 9 wt. % Al with around 1 wt. % Zn in each alloy. This alloy system has been characterized as showing second phases forming at grain boundaries and interdendritic regions. Heterogeneities in the microstructure can vary the electrochemical potentials of the material, making them instrumental in understanding the corrosion behavior of this alloy system. From microstructural investigation, an increase in Al content increased the volume fraction and segregation of secondary phase, β. This change in microstructure showed a clear difference in corrosion morphology among alloys. Mg and its alloys form Mg oxide films in ambient conditions and Mg hydroxide in aqueous conditions. Studies have shown an inhibiting effect when Mg is in the presence of atmospheric carbon dioxide (CO2). An increase in Al content has shown to have a positive effect on corrosion performance of Mg alloys. In laboratory conditions, most tests are done in bulk solution which can limit the access of CO2 at the surface of the alloy. A simple immersion experiment was conducted to demonstrate the effect that experimental set up can have on corrosion behavior. The amount of CO2 available at the surface of the alloy is changed by varying solution height. It was shown that the interfacial pH attained a high value due to the overwhelming effect of hydrogen evolution, while the bulk solution remained buffered by the CO2. The effect of CO2 on Mg alloys was studied by testing various AZ series alloys in the presence and absence of CO2. This study aimed to identify a possible interaction between Al content and CO2 that affects the corrosion rate. Electrochemical testing was done using electrochemical impedance spectroscopy (EIS) to und (open full item for complete abstract)

Committee: Rudolph Buchheit (Advisor); Gerald Frankel (Advisor); Christopher Taylor (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2019, Materials Science and Engineering

Metal-rich primers have been used for corrosion protection on metals for over 40 years. Recently, researchers started to investigate the use of metal-rich primers on aluminum alloys as an alternative to hexavalent-chromate systems because of their good corrosion-protective properties. The active aluminum-rich primer (AlRP) was invented and developed at NAVAIR (Patuxent River, MD) to protect aluminum alloys and steels. The Al alloy (Al-Zn-In) pigments in AlRP were fabricated from a sacrificial anode alloy, which has a lower open circuit potential (OCP) than common aluminum alloys. However, initial results indicated that the pigment particles in AlRP tended to undergo severe self-corrosion. Therefore, the Al pigments are pretreated in a trivalent chromium passivation (TCP) bath to reduce the self-corrosion rate. The objectives of this study are to understand the corrosion protection properties of AlRP on aluminum alloy 2024-T3 substrate and to evaluate the effect of TCP treatment on the Al pigment particles. The polarization curves of AA2024-T3 and the active aluminum alloy (Al-Zn-In) show that TCP-treated active aluminum alloy has a lower corrosion potential than AA2024-T3 and thus would cathodically protect it. AlRP-coated samples were exposed in accelerated exposure tests, GMW14872 and B117. Exposed samples were then examined using scanning electron microscopy and energy dispersive X-ray spectroscopy to understand the coating degradation process. In addition, samples were immersed in 0.1M NaCl solution for an extended time and were monitored using electrochemical impedance spectroscopy. The AlRP with TCP-treated pigments out performs the coating with untreated pigments. The TCP treatment on the Al-Zn-In pigments was evaluated. The chemistry and morphology of Al pigment particles treated in a TCP bath for three different immersion times were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and ener (open full item for complete abstract)

Committee: Gerald Frankel (Advisor); Jenifer Locke (Committee Member); Narasi Sridhar (Committee Member) Subjects: Materials Science

Master of Science in Renewable and Clean Energy Engineering (MSRCE), Wright State University, 2018, Mechanical Engineering

With the rise of electric vehicles and increasing dependence on mobile electronics, the demands for lithium-ion batteries have followed in tandem for their high energy and power densities. However, traditional lithium-ion batteries consisting of liquid electrolytes have limited operating temperatures and are susceptible to ignition and subsequent fires. Recently, battery research has diverged into solid state chemistry to address the aforementioned issues. In this research, we systematically investigate a series of ceramic/polymer lithium-ion conducting composite electrolytes, i.e. Li1.4Al0.4Ge1.6(PO4)3 /lithiated polyethylene oxide (LAGP/PEO). Lithiated PEO was prepared with two different lithium salts, LiBF4 and LITFSI. The impacts of the LAGP on the electrical, thermal, and mechanical properties of the two lithiated PEO systems are assessed. When LAGP is homogenously distributed in PEO-LiTFSI films, ionic conductivities and thermal properties remain relatively uninhibited; the elastic modulus and ultimate strength increased up to 450% and 200%, respectively. When LAGP was added to PEO-LiBF4 films, it increased the elastic strength nearly 200% without compromising the ultimate strength and thermal properties, but at the sacrifice of ionic conductivity. The ceramic/polymeric electrolytes have potential applications to flexible all solid state lithium-ion batteries.

Committee: Hong Huang Ph.D. (Committee Chair); James Menart Ph.D. (Committee Member); Thomas Howell Ph.D. (Committee Member); Michael Rottmayer Ph.D. (Committee Member) Subjects: Alternative Energy; Energy; Engineering; Materials Science; Solid State Physics; Technology

Master of Environmental Science, Miami University, 2017, Environmental Sciences

The internship was completed from December 16, 2013, till July 31, 2016, at the Armenian Water and Sewerage Closed Joint Stock Company (AWSC), Investment Programs Coordination Directorate, Head office, Yerevan, Republic of Armenia. The main project of the internship was “Water Supply and Sanitation Sector Project - Additional Financing” funded by the Asian Development Bank (ADB). I was involved in the project as an Environmental and Social Impact Specialist. This report describes the tasks and assignments for which I was responsible.

Committee: Amélie Davis PhD (Advisor); Vincent Hand PhD (Committee Member); Jonathan Levy PhD (Committee Member) Subjects: Environmental Management

Master of Sciences, Case Western Reserve University, 2017, Materials Science and Engineering

The performance of solid oxide fuel cells (SOFCs) with three different lanthanum strontium manganite (LSM) based cathode compositions were evaluated. All cells were yttria-stabilized zirconia (Zr0.92Y0.08O2-d, 8YSZ) electrolyte-supported button cells, consisting of a nickel oxide – yttria-stabilized zirconia (NiO-8YSZ) anode and a cathode of 8YSZ and LSM. The three LSM compositions differed in the amount of excess Mn: Composition A was (La0.85Sr0.15)0.90MnO3±d (10% excess Mn); Composition B was (La0.80Sr0.20)0.95MnO3±d (5% excess Mn); and Composition C was (La0.80Sr0.20)0.98MnO3±d (2% excess Mn). The cells were tested under conventional and accelerated conditions, where the accelerated conditions were meant to simulate the results of months of long-term testing in just 500 hours (approximately three weeks) of testing by using high operating temperature and current density. Accelerated tests showed lower degradation rates, lower continuous area specific resistance (ASR), and higher power output than conventional tests for all cathode compositions. Continuous measurements of the cells' output voltage versus time, together with periodic electrochemical impedance spectroscopy (EIS) measurements, were used to evaluate the performance of the cells in terms of ASR degradation rates (% ASR rise per kh) and power outputs. The EIS measurements also permitted a partial deconvolution of the cathode ASR from the anode ASR. Cathodes with 10% excess Mn tested under accelerated conditions had the lowest degradation rates, but the highest continuous ASR and lowest power outputs. Cathodes with 2% excess Mn tested under accelerated conditions had the lowest continuous ASR and highest power outputs; thus it was concluded that cells with the lowest amount of excess Mn cathodes performed the best.

Committee: Mark De Guire (Advisor); Arthur Heuer (Committee Member); Roger French (Committee Member) Subjects: Energy; Materials Science

Doctor of Philosophy, University of Akron, 2016, Chemical Engineering

Zinc rich primers (ZRPs) have been widely applied in metallic structures especially for iron, due to its sacrificial cathodic protection and barrier protection. The main factor that influences its anticorrosion performance is the electrical connection between zinc particles, considered as percolation. The objective of this work is to improve the anticorrosion performance of a commercial ZRP by using an intrinsically conductive polymer (ICP). Of the commonly available ICPs, polyaniline (PAni) was chosen due to its high stability and simple synthesis using its monomer aniline. Different states of PAni including nonconductive emeraldine base (EB) and conductive emeraldine salt (ES) were added to ZRP, to study the effects of the different oxidation states on anticorrosive performance. Considering conductive state ES, the effects of different dopants have been investigated on corrosion prevention behavior of PAni containing ZRPs using multi-tool techniques, including camphor-10-sulfonic acid (CSA), phenylphosphonic acid (H2PP), hydrochloride acid (HCl) and phosphoric acid (H3PO4). In addition, to improve the protective performances of ZRP combined with PAni doped with CSA, higher contents of conductive pigment and multiwall carbon nanotube (MWCNT) were considered. Also, the zinc oxide nanoparticles were added into ZRP with PAni doped by H2PP acid, to check the combination effect of PAni and ZnO nano powder in coating performance. The corresponding corrosion mechanisms were proposed, based on the coating properties and results of an immersion test and open circuit potential, electrochemical, and localized electrochemical tests. The addition of a small amount of conductive PAni to ZRP slowed the activation process of zinc particles and further improved the cathodic protection effect. It also provided better barrier performance compared with the commercial ZRP. The nonconductive PAni EB accelerated the activation of zinc particles, and the formed zinc oxide products wer (open full item for complete abstract)

Committee: Homero Castaneda Lopez (Advisor); Hongbo Cong (Committee Chair); Qixin Zhou (Committee Member); Xiaosheng Gao (Committee Member); Kevin Kreider (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Akron, 2016, Chemical Engineering

Corrosion inhibitors as effective anti-corrosion applications were widely studied and drawn much attention in both academe and industrial area. In this work, a systematic work, including inhibitors selection, anti-corrosion property and characterization, influence on scale formation, testing system design and so on, were reported. The corrosion inhibition performance of four imidazolium ionic liquids in carbon dioxide saturated NaCl solution was investigated by using electrochemical and surface analysis technologies. The four compounds are 1-ethyl-3-methylimidazolium chloride (a), 1-butyl-3-methylimidazolium chloride (b), 1-hexyl-3-methylimidazolium chloride (c), 1-decyl-3-methylimidazolium chloride (d). Under the testing conditions, compound d showed the highest inhibition efficiency and selected as the main object of further study. As a selected representative formula, 1-decyl-3-methylimidazolium chloride was studied in detail about its corrosion inhibition performance on mild steel in carbon dioxide saturated NaCl brine at pH 3.8 and 6.8. Electrochemical and surface analysis techniques were used to characterize the specimen corrosion process during the immersion in the blank and inhibiting solutions. The precorrosion of specimen surface showed significant and different influences on the anti-corrosion property of DMICL at pH 3.8 and 6.8. The corrosion inhibition efficiency (IE) was calculated based on parameters obtained from electrochemical techniques; the achieved IE was higher than 98% at the 25th hour for the steel with a well-polished surface at pH 3.8. The fitting parameters obtained from electrochemical data helped to account for the interfacial changes. As proved in previous research, 1-decyl-3-methylimidazolium chloride could be used as good corrosion inhibitors under certain conditions. However, under other conditions, such chemicals, as well as other species in oil transporting system, could be a factor influencing the evolution of protective (open full item for complete abstract)

Committee: Homero Castaneda (Advisor); Hongbo Cong (Committee Chair); Qixin Zhou (Committee Member); Xiaosheng Gao (Committee Member); Yi Pang (Committee Member) Subjects: Chemical Engineering; Materials Science

Master of Science in Engineering, University of Akron, 2015, Chemical Engineering

This work describes the testing performed for corrosion control actions for X-52 carbon steel in ethanol media by using inhibitors, the following compounds were included: linalyl formate, linalyl acetate, linalyl butyrate, citronellyl acetate and 1-pentylallyl acetate. The experiments were performed in an electrochemical 3 electrode system with an X-52 steel rotating cylinder electrode (RCE) with rotational speed adjusted to 130 RPM. The system was deaerated by bubbling nitrogen gas into the ethanol solution. The Electrochemical Impedance Spectroscopy (EIS) technique was used to characterize the metal/electrolyte interface. Experimental testing was performed in anhydrous ethanol solution with 5 mM or 10 mM of one inhibitor. Surface analyses for the corroded surfaces were obtained by scanning electron microscopy (SEM) and White light interferometry (WLI). The results suggest that linalyl formate promotes the highest corrosion inhibition efficiency at 10 mM, followed by citronellyl acetate and linalyl butyrate. At this concentration, 1-pentylallyl acetate and linalyl acetate have not promoted corrosion inhibition. At a concentration of 5 mM, linalyl formate, linalyl acetate and linalyl butyrate promoted high inhibition efficiencies during the first hours but none was able to promote a longer protection than one day, possibly due to chemical degradation, chemical reactions and/or reduced surface coverage. The linalyl formate is considered the best chemical for inhibition purposes, especially at the concentration of 10 mM.

Committee: Homero Castaneda-Lopez Dr. (Advisor); Hongbo Cong Dr. (Committee Member); Qixin Zhou Dr. (Committee Member) Subjects: Chemical Engineering; Materials Science

Doctor of Philosophy, University of Akron, 2015, Mechanical Engineering

A global study performed in 1966 revealed that nearly 30% of the energy produced is spent to overcome friction and associated losses. A new interdisciplinary domain "Tribology" was defined in the "Jost Report"' as the branch of science that essentially deals with friction, wear and lubrication. Increasing demand to improve efficiency of mechanical systems has stimulated the research in tribology over the last few decades. Surface engineering methods are state of art techniques that are being adapted by industries including bearing manufacturers to address friction and wear issues. Many new and novel coatings have been developed for specific applications, but few if any, have improved the tribological performance of the most widely used components: ball bearings. Thus, there is a need for new tribological research designed to understand the influence of the coatings deposited onto spherical rolling elements in tribological contacts, and minimize losses due to friction and wear. In this work, thin films were deposited onto spherical rolling elements and the performance of the coated balls was evaluated under different conditions. The study revealed that ball coatings improves the performance of bearings, but coatings need to be selected based on application requirements to avail the benefits of coated balls.

Committee: Gary Doll (Advisor) Subjects: Mechanical Engineering

Doctor of Philosophy, University of Akron, 2015, Chemical Engineering

The Al - Li 2060 aluminum lithium alloy was first launched in 2011. This alloy is a potential candidate for the use at wing/fuselage forgings, lower wing, and fuselage/pressure cabin. However, since its first launching, the corrosion properties of this alloy has not been extensively explored. There are three common laboratory tests for assessing the exfoliation corrosion (EFC) susceptibility of aluminum alloy 2XXX, namely EFC test in EXCO, modified EXCO and MASTMAASIS media. The objectives of this work is to study the susceptibility and mecahnism of corrosion of this alloy in EXCO, modified EXCO and MATSMAASIS media. These three media are acid. In the EXCO solution, this alloy suffers EFC after a 96-hour EFC test. The pH dramatically increases in the first 11 hours from 0.25 to 0.30. The pH then slightly increases and tends to remain constant at pH of 3.45 after 96 hours. The cyclic potentiodynamic polarization (CPP) test results show the presence of negative hysteresis and one breakdwon potential. This negative hysteresis suggests the absence of pitting corrosion due to the breakdown of passive film. The potentiostatic tests at potentials below and above the breakdown potential show an abrupt increase in potential in the first minutes and the presence of current transients. The scanning electron microscopy (SEM)-energy dispersive x-ray spectroscopy (EDS) examination confirms that the Al20Cu2Mn3 particles preferentially dissolve, leaving the pitting after a potentiostatic test below the breakdown potential. From the potentiostatic test at a potential above the breakdown potential and an SEM examination after this potentiostatic test, intergranular corrosion (IGC) was observed. The electrochemical impedance spectroscopy (EIS) test and mathematical modeling indicates that the adsorption of intermediates in reduction of hydrogen ions is dominant in the first hours of immersion. The two time constants are observed when EFC occurs. The video capture microscopy obviou (open full item for complete abstract)

Committee: Homero Castaneda Dr (Advisor); Scott Lillard Dr (Committee Member); Zhenmeng Peng Dr (Committee Member); Xiaosheng Gao Dr (Committee Member); John Senko Dr (Committee Member) Subjects: Chemical Engineering; Materials Science

Master of Science in Engineering, University of Akron, 2015, Chemical Engineering

The internal susceptibility and corrosion of pipelines has widely been minimized by the use of inhibitors which mitigate and control degradation effects due to flow conditions and to aggressive environments created inside the pipeline. However, environmental hazard might constitute a problem due to the chemical substances forming the inhibitors. A very specific application of pipeline integrity occurs in offshore facilities for oil recovery production where a mixture of pressurized water-CO2 is injected to almost depleted oil wells in order to enhance recovery. As CO2 injection is very common in marine environments, the effect of chloride ions is added to the corrosive variables of the system is considered. Environmental aggressiveness is set due to a paired effect of environmental conditions: the formation of carbonic acid in the water-CO2 mixture and the presence of chloride ions as part of the marine environment. Here we aimed to electrochemically characterize a zinc-rich epoxy nanocoating primer (ZREP), as well as a composite variation incorporating carbon nanotubes (CNT-ZREP), on an API X52 pipeline grade steel substrate. A rotating cylinder electrode (RCE) was used to incorporate the flow regime and equivalent shear stress conditions. The selected electrolyte for testing was 3% (wt.) NaCl saturated with CO2. The anti-corrosion properties of these nanocomposite coatings are a result of the combined effects of Zn and C nanoelements, which impart special properties not initially inherent in the matrix or in the nanoelements. The effects of these medium conditions on the performance of the substrate/coating system were characterized in real-time by electrochemical impedance spectroscopy. The damage evolution concept was adopted to analyze the current stages and to propose possible mechanisms for the roles of the CNTs and Zn cathodic in providing enhanced protection to the substrate.

Committee: Homero Castaneda-Lopez Dr. (Advisor); Qixin Zhou Dr. (Committee Member); Rajeev Gupta Dr. (Committee Member) Subjects: Chemical Engineering; Chemistry; Engineering

Master of Science in Engineering, University of Akron, 2015, Chemical Engineering

Al 2024 T-3 is a commonly used alloy in the aircraft industry which is highly susceptible to localized corrosion when subjected to corrosive environments. Of the many corrosion protection systems, applying a coating is one of the most cost effective methods. The classical physical barrier properties offered by the coatings in combination with a galvanic sacrificial anode offers to extend the life of the alloy against corroding environments. Since, aluminium is already at a lower position in the galvanic series; it must be protected by a more active material. Hence, a magnesium enriched coating is suggested for protection of such alloys. The present research aims at characterizing a magnesium rich primer (MgRP) applied over Al 2024 T-3 substrate. The Al 2024 T-3 substrate was pre-treated with PreKote to enhance the electrical contact between the magnesium particles and the substrate to activate the galvanic cathodic protection. Electrochemical Impedance Spectroscopy is used to characterize the interfacial mechanisms existing at the substrate/electrolyte interface. The MgRP/Al 2024 T-3 system is subjected to 0.6M NaCl solution to emulate the sea water conditions; and 0.6M sodium sulphate solution to emulate the acid rain conditions. The coating characteristics were varied on Al 2024 T-3 substrates in order to compare the response of the interface, and to study the existing transport mechanism of the coating layer. The interfacial reactions are being studied to determine the corrosion mechanism within the formed layer based on the damage evolution concept. Electrochemical characterization of the system was carried out by monitoring the coating/substrate/electrolyte interface in real time. The multi-scale theoretical tools which comprise of electrochemical testing techniques, high surface resolution techniques and characterization methods, analyse the performance of the substrate/coating interface with respect to the physical characteristics (thickness and environmen (open full item for complete abstract)

Committee: Homero Castaneda-Lopez Dr. (Advisor); Qixin Zhou Dr. (Committee Member); Rajeev Gupta Dr. (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, University of Akron, 2015, Chemical Engineering

Zinc rich epoxy primers are an effective corrosion protection method to protect the steel structures against an aggressive environment. An aggressive environment like marine environment (high content in chloride ions) degrades the metal structure until a complete failure of the metal system. A way to avoid the degradation is to isolate the system form the environment. Zinc rich primers protect the steel by the sacrificial action of the zinc dust particles. A zinc corrosion products barrier layer protects the steel by blocking the passage of the aggressive species like oxygen and chlorides that favor the cathodic reaction. In this thesis, the corrosion protection properties of a commercial formulation (zinc rich primer with CNTs) system and prototype formulations (Zn/CNTs ratios) were studied as a function of the immersion time. Electrochemical corrosion measurements were implemented in non-dearated electrolytes of 0.6M NaCl (3.5 wt% NaCl) in distilled water with a pH=6. Besides the NaCl solution, alkali-halides solution identify the chloride effect with the change in the cation. The transport properties of these solutions defined the 0.6M NaCl the more aggressive solution to the bare metal and the coating-metal system.. Electrochemical Impedance Spectroscopy is the main AC technique to characterize the system and the DC Polarization curves, potentiostatic (galvanic couple) and OCP. Localized electrochemical impedance characterizes the commercial system to define the anodic and cathodic zone once the sample is immerse in the solution. ASTM-B117 was employed to evaluate the commercial and the prototye system. The samples were divided into two sections and one with 1 inch long indentation and tested by 30 days. High resolution techniques like an atomic force microscope (AFM) and scanning electron microscopy (SEM), characterizes the surface before and after immersion. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) identify the corrosion product (open full item for complete abstract)

Committee: Homero Castaneda Dr. (Advisor); Scott Lillard Dr. (Committee Member); Bi-min Zhang Newby Dr. (Committee Member); Mark Soucek Dr. (Committee Member); Chelsea Monty Dr. (Committee Member) Subjects: Chemical Engineering; Materials Science; Metallurgy

Master of Science, University of Akron, 2014, Chemical Engineering

Aluminum 2024-T3 and 7075-T6 are commonly used in aviation industry. The coating application on the aluminum surface is consider as one of the most effective method to ease the corrosion problem. Hex-chrome free coating which has less environmental issues was developed in recent years. In this work, we studied the degradation process of hex-chrome free coating/ aluminum system under the constant immersion environment with the help of a proposed damage evolution concept. This damage evolution concept includes four steps: 1. Initial water uptake process within coating layer, 2. Activation of electrochemical reaction in the coating and metal interface 3. Propagation of corrosion products below coating layer, coating delamination or degradation. 4. Coating totally fails, metal experiences severe metal loss. Three experimental variables were investigated in this project, they were: pH of electrolyte, top coat thickness, and metal effect. Impedance measurements of samples immersed in 3.5 wt% NaCl electrolyte were continually carried out for 160 days to study the impact of those experimental variables. A two dimensional transmission line model was developed in this work. This 2D-TLM was firstly verified via comparing the simulated EIS data with experimental results. A further application of this model gave us a local impedance distribution of hex-chrome free coating/aluminum profile. Via interpreting the local impedance distribution, a detailed degradation mechanism of sample in early immersion period was revealed.

Committee: Homero Castaneda-Lopez Dr. (Advisor); Scott Lillard Dr. (Committee Member); Hongbo Cong Dr. (Committee Member) Subjects: Chemical Engineering

PhD, University of Cincinnati, 2009, Engineering : Materials Science

The following work is the study to evaluate the impact of corrosion inhibitors on the copper metal in drinking water and to investigate the corrosion mechanism in the presence and absence of inhibitors. Electrochemical experiments were conducted to understand the effect of specific corrosion inhibitors in synthetic drinking water which was prepared with controlled specific water quality parameters. Water chemistry was studied by Inductively Coupled Plasma–Atomic Emission Spectroscopy (ICP–AES) to investigate the copper leaching rate with time. Surface morphology, crystallinity of corrosion products, copper oxidation status, and surface composition were characterized by various solid surface analysis methods, such as Scanning Electron Microscopy/Energy–Dispersive Spectrometry (SEM/EDS), Grazing-Incidence-angle X-ray Diffraction (GIXRD), X-ray Photoelectron Spectroscopy (XPS), and Time-of-Flight Secondary Ions Mass Spectrometry (ToF-SIMS). The purpose of the first set of experiments was to test various electrochemical techniques for copper corrosion for short term before studying a long term loop system. Surface analysis techniques were carried out to identify and study the corrosion products that form on the fresh copper metal surface when copper coupons were exposed to test solutions for 2 days of experiments time. The second phase of experiments was conducted with a copper pipe loop system in a synthetic tap water over an extended period of time, i.e., 4 months. Copper release and electrochemically measured corrosion activity profiles were monitored carefully with and without corrosion inhibitor, polyphosphate. A correlation between the copper released into the solution and the electrochemically measured corrosion activities was also attempted. To investigate corrosion products on the copper pipe samples, various surface analysis techniques were applied in this study. Especially, static mass spectra acquisition and element distribution mapping were carried out by (open full item for complete abstract)

Committee: William Vanooij PhD (Committee Chair); Jude Iroh PhD (Committee Member); Relva Buchanan ScD (Committee Member); Darren Lytle PhD (Committee Member) Subjects: Materials Science

MS, University of Cincinnati, 2005, Engineering : Materials Science

This work deals with the development of a non-chromate, one-step finishing system for corrosion protection of hot-dip galvanized steel. Environmental regulations demand that chromate pretreatments and chromate pigments used in primers be replaced. In this project a pretreatment-free, chromate-free one-step finishing system was needed for hot-dip galvanized steel used in automotive coils in cars. Pretreatments act as adhesion-promoters and bind coatings to metals and since silanes, especially systems using bis-amino silane and bis-sulfur silane, have been shown as excellent adhesion-promoters by this lab, the idea of incorporating silanes in primers for obtaining adhesion to metals emerged. Whether this also meant increased corrosion protection was investigated. It was clear from the performance results and characterization experiments that silanes perform positively, in terms of enhanced corrosion protection of the metal substrate and adhesion. The polyurethane network resulted from the curing agent-resin reaction. A chromate-free, one-step finishing system without need for pretreatment and exhibiting enhanced corrosion protection and adhesion to metal was developed.

Committee: Dr. Wim Van Ooij (Advisor) Subjects:

PhD, University of Cincinnati, 2005, Engineering : Materials Science

The need for toxic chromate replacements in metal-finishing industries has prompted an intensive search for replacement technologies in recent years. Among the replacements that have been proposed, those that are based upon the use of organofunctional silanes rank very high in terms of performance, broad applicability as well as ease of application. This dissertation presents a four-part work: (1) structural characterization of silane films on metals, (2) mechanism studies of silane-treated metal systems, (3) development of water-based silane systems, and (4) measurements of other properties of silane films. In part 1, silane films, i.e., bis-[triethoxysilylpropyl]tetrasulfide (bis-sulfur silane) and bis-[trimethoxysilylpropyl]amine (bis-amino silane) were deposited on AA 2024-T3 and were characterized mainly using reflection-absorption Fourier-transform infrared spectroscopy (FTIR-RA) and electrochemical impedance spectroscopy (EIS) techniques. The results showed that further hydrolysis and crosslinking occurs in the applied bis-sulfur silane films in the presence of water and moisture. This is because the bis-sulfur silane is difficult to hydrolyze completely in its water/ethanol solution. The remaining ester groups would hydrolyze to silanols when water or moisture presents (e.g., in the processes of curing in the atmosphere and immersion in an aqueous solution). The as-formed silanols would further condense either with themselves or with aluminum hydroxyl groups at the alloy surface, forming siloxanes and aluminum-siloxanes. Three different regions were clearly detected by EIS in the bis-sulfur silane-treated AA 2024-T3 system, and were further observed in the SEM/EDX studies. According to these studies, the three regions are assigned to, from outside to inside, outermost silane film dominated with siloxanes (SiOSi), interfacial layer with both siloxanes and aluminum-siloxanes (AlOSi), and innermost aluminum oxide. In part 2, the mechanistic study of corrosion p (open full item for complete abstract)

Committee: Dr. Wim van Ooij (Advisor) Subjects: Engineering, Materials Science