Thin polymeric coatings have been applied to metal surfaces to prevent and/or prolong the onset of fretting corrosion, but the properties that make a polymeric coating effective and the means by which a coating fails are unknown. The purpose of this study was to determine the effect of molecular weight, casting solvent, and amplitude of motion on the life of thin (25 ~m nominal) polystyrene coatings. Narrow molecular weight distribution polystyrene coatings ranging from <Mw>=19,400 to <Mw>=1,460,000 were applied to UNS G10450 steel disks with toluene and MEK as casting solvents. The coatings were fretted against UNS G52100 steel balls at 20 Hz under 22.3 N normal load. Amplitudes of motion ranged from 100 ~m to 500 ~m. Coating life and friction force were measured. Coatings of <Mw>=207,700 showed maximum life at all amplitudes. Friction remained constant for all tests, and increasing amplitude decreased life. Toluene-cast coatings had slightly shorter lives and more coating racks than MEK-cast coatings. Toluene-cast coatings below <Mw>=53,700 cracked severely during solvent removal and were not tested. / Master of Science

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: The coating thermal conductivity, the effective coated-tube thermal conductivity and the coating factor of three artificial protective coatings (APCs) applied to condenser tubes are experimentally evaluated. This testing broadens the limited available knowledge of these coatings, which is necessary for effective condenser refurbishment and operation. The coatings are applied to 25.4 mm brass tubes at thicknesses of 44, 46, 50, and 130 μm. Steady state heat transfer tests are performed on these tubes fitted in a double-pipe counter-flow heat exchanger, with heated water in the annulus and coolingwater inside the tube. The experimentally determined thermal conductivities of the coatings range from 0.5 to 2.3 W/m·K. The effective coated-tube conductivity and the coating factor depend on the tube material and size, as well as the coating thickness. A one-dimensional condenser model is used to parametrically investigate the relative overall effect on condenser performance. From these results, coating guidelines for Admiralty brass tubes are proposed in terms of the minimum and maximum coating conductivity and thickness. The effect of the coating on the thermal performance is equivalent to a Heat Exchange Institute (HEI) cleanliness factor of at least 0.85, when adhering to these guidelines. APCs provide a layer of protection against corrosion, erosion and fouling and can preferentially fill tube-wall pits. They can therefore be used to extend the condenser life-span effectively, but, to ensure minimal impact on the overall condenser performance, the coating thickness and conductivity must be carefully controlled and verified experimentally. / AFRIKAANSE OPSOMMING: Die termiese geleidingsvermoë, die effektiewe termiese geleidingsvermoë van bedekte buise en die bedekkingsfaktor van drie kunsmatige beskermingsbedekkingslae wat op kondensorbuise aangewend word, word eksperimenteel geëvalueer. Hierdie evaluering verbreed die beperkte beskikbare kennis oor sodanige bedekkingslae, wat nodig is vir effektiewe kondensor herinrigting en bedryf. Die lae word teen diktes van 44, 46, 50 en 130 μm in 25.4 mm geelkoperbuise aangewend. Warmteoordragstoetse by gestadigde toestande word gedoen op hierdie buise in ’n dubbelpyp-teenvloeiwarmteoordraer, met verhitte water in die annulus en verkoelingswater binne-in die buis. Die eksperimenteel bepaalde termiese geleidingkoëffisiënte wissel tussen 0.5 tot 2.3 W/m·K. Die effektiewe geleidingsvermoë en bedekkingsfaktor hang af van sowel die buis se materiaal en grootte sowel as die dikte van die bedekkings. ’n Eendimensionele kondensormodel word gebruik om die algehele effek van hierdie beskermingsbedekkingslae op kondensorwerkverrigting parametries te ondersoek. Riglyne ten opsigte van aanwending van beskermingslae vir buise van “Admiralty” geelkoper word verskaf in terme van die minimum en maksimum geleidingsvermoë en dikte van bedekkingslae. Met behulp van hierdie riglyne word ’n “Heat Exchange Institue” (HEI) ekwivalente skoonheidsfaktor van minstens 0.85 op ’n nuwe buis behaal. Hierdie kunsmatige bedekkingslaeslae bied beskerming teen korrosie, erosie en bevuiling en kan klein kuile in die buiswand vul. Hulle kan dus gebruik word om die lewensduur van die kondensator te verleng, maar hul dikte en geleidingsvermoë moet noukeurig beheer word en moet eksperimenteel geverifieer word.

Industrial and power generation processes employ units like boilers and gasifiers to burn sulfur containing fuels to produce steam and syn gas (H2 and CO), which can generate electricity using turbines and fuel cells. These units often operate under environments containing gases such as H2S, SO2, O2 etc, which can attack the metallic structure and impose serious problems of corrosion. Corrosion control in high temperature sulfur bearing environments is a challenging problem requiring information on local gaseous species at the surface of alloy and mechanisms of degradation in these environments. Coatings have proved to be a better alternative for improving corrosion resistance without compromising the bulk mechanical properties. Changes in process conditions may result in thermal and/or environment cycling between oxidizing and sulfidizing environments at the alloy surface, which can damage the protective scale formed on the alloy surface, leading to increase in corrosion rates. Objective of this study was to understand the effect of fluctuating environments on corrosion kinetics of carbon steels and develop diffusion based coatings to mitigate the high temperatures corrosion under these conditions. More specifically, the focus was : (1) to characterize the local gaseous environments at the surface of alloys in boilers; (2) optimizing diffusion coatings parameters for carbon steel; (3)understand the underlying failure mechanisms in cyclic environments; (4) to improve aluminide coating behavior by co-deposition of reactive elements such as Yttrium and Hafnium; (5) to formulate a plausible mechanism of coating growth and effects of alloying elements on corrosion; and (6) to understand the spallation behavior of scale by measuring stresses in the scales. The understanding of coating mechanism and effects of fluctuating gaseous environments provides information for designing materials with more reliable performance. The study also investigates the mechanism behind the effect of REs on scale adhesion and sulfidation behavior. Thus, the present work will have a broad impact on the field of materials and coatings selection for high temperature industrial environments such as boilers and gasifiers, and provides information on RE-modified aluminized coatings on carbon steel as an alternative for the use of bulk superalloys under high temperature sulfur bearing environments.

Biologically inspired design is used as an approach for sustainable engineering. Taking a biologically inspired approach, one abstracts ideas and principles from nature, an inherently sustainable system, and uses them in engineering applications with the goal of producing environmentally superior designs. One such biological idea with potential environmental benefits for engineering is microscale and nanoscale surface roughness found on the Lotus plant and many other surfaces in nature. These surfaces repel water and aid in contaminant removal; this self-cleaning phenomenon is called the "Lotus Effect," in honor of the plant first observed to exhibit it. The structures responsible for the Lotus Effect inspired research and development of many technologies capable of creating hydrophobic, self-cleaning surfaces, and many potential self-cleaning surface applications exist beyond nature's intended application of cleaning. While statements have been made about the environmental benefits of using a self-cleaning surface, only limited scientific data exist. Artificial self-cleaning surfaces are successfully cleaned using fog or mist. This shows that such surfaces can be cleaned with less energy and water intensive methods than the more conventional methods used to clean regular surfaces, such as spray or solvent cleaning. This research investigates the potential environmental burden reductions associated with using these surfaces on products. A life cycle assessment is performed to determine the environmental burdens associated with manufacturing a self-cleaning surface, for three production methods: a chemical coating, a laser ablated steel template, and an anodized aluminum template. The environmental benefits and burdens are quantified and compared to those of more conventional cleaning methods. The results indicate that self-cleaning surfaces are not necessarily the environmentally superior choice.

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Joseph B. Schlenoff, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Feb. 1, 2006). Document formatted into pages; contains xvii, 167 pages. Includes bibliographical references.

Made available in DSpace on 2014-10-09T12:46:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:32Z (GMT). No. of bitstreams: 1 07616.pdf: 6459739 bytes, checksum: 6032bfb27763f826fa1eef8e9dacd71f (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:46:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:32Z (GMT). No. of bitstreams: 1 07616.pdf: 6459739 bytes, checksum: 6032bfb27763f826fa1eef8e9dacd71f (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Thesis (MBA)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Retailing is a common modern day phenomenon for which there are many angles of research widely and easily available. Retailing in the context of the global paint and coatings industry however, is a more specified and unique field of study of which resources for research are few. Having had the opportunity of a first-hand close-up inside look into, not only one of the world’s leading paint and coatings companies, but also the global leader in company-owned paint and coatings retailing. This global leader not only led to the origin of my research, but also rekindled the passion within for the global paint and coatings industry and trade. Prior to my employment by PPG, towards the end of 2013, I intentionally embarked on a journey with The Sherwin Williams Company during 2011 to 2013, in collaboration with my current employer at the time, Duraline paints, who afforded me the opportunity only a few people had or ever will.. During the course of four years, I had the opportunity to not only meet a series of wonderful people across the various segments, as well as internal departments of the Sherwin Williams Company globally. Additionally I also had the opportunity to visit the company’s headquarters, 101 Prospector Avenue, Cleveland, Ohio, on numerous occasions whilst staying in close proximity for the duration of the training and strategic planning sessions, in preparation to duplicate the SHW in South Africa. During my involvement with The Sherwin Williams Company, it was evident that the backbone of the company’s sales model, was the consistency as well as continuous growth of the Paint Stores Group; which is the leading North American retail segment of SHW. Since 2011, in an effort to establish the best method of implementation of this sales model in South Africa, various concepts were explored from several angles. It became evident that much research was required to establish feasibility of the SHW sales model in South Africa. Preliminary research however, would have had to be conducted of what the SHW sales model entailed and how it would benefit the company in being a global leader, thereby also exploring the possibility of it being an industry best practice as foundation to what was precisely required to be implemented in South Africa, prior to establishing feasibility in South Africa. The preliminary research became the primary and sole focus of this research project, not only fulfilling the research needs as explained above, but also to serve as evidence of what I perceived the SHW company and the Paint Stores Group to be whilst dealing with the company.

The metallic alloys employed in oxidizing environment at high temperature rely on the development of a protective oxide scale to sustain the long-term aggressive exposition. However, the oxide scale growth is most of the time coupled with stress and morphological developments limiting its lifetime and then jeopardizing the metallic component reliability. In this study, a mechanism of local stress effect on the oxidation kinetics at the metal/oxide interface is investigated. The objective is to improve the understanding on the possible interactions between stress generation and non-uniform oxide scale growth, which might result in a precipitated mechanical failure of the system. Two different oxides are studied, alumina and chromia, in two different industrial systems, thermal barrier coatings and solid oxide fuel cell interconnects. A specific thermodynamic treatment of local oxide phase growth coupled with stress generation is developed. The formulation is completed with a phenomenological macroscopic framework and a numerical simulation tool is developed allowing for realistic analyses. Two practical situations are simulated and analyzed, concerning an SOFC interconnect and a thermal barrier coating system, for which oxide scale growth and associated stress and morphological developments are critical. The consequence of the non-uniform oxide growth on the system resistance to mechanical failure is investigated. Finally, the influences of material-related properties are studied, providing optimization directions for the design of metallic alloys which would improve the mechanical lifetime of the considered systems.

Modification of the surface chemistry of materials used as implants in biomedical applications affords the ability to control cell adhesion, prevent inflammation and enhance integration with the host. Titanium and its alloys are strong and lightweight thereby making them desirable for applications such as hip and knee replacements, dental implants, and cardiac pacemaker implants. However, the lifetime of these implants is often limited by poor incorporation into the surrounding bone which results in loosening and wear. In order to overcome these limitations we have studied the modification of titanium substrates with a self-assembled monolayer that can be used to perform surface-initiated atom transfer radical polymerization (SI-ATRP) of a monomer to afford polymer brushes that effectively prevent the adhesion of cells. In addition, the polymer brushes afford the ability to tether a peptide sequence. Specific peptides containing adhesion sequences have been tethered to the polymer brushes. The resulting surfaces promote cell adhesion and osteoblast differentiation, thereby increasing bone tissue formation around the implant resulting in better incorporation of the implant.