Solvent-borne thermally cured coil-coating resins contain large amounts of volatile organic solvents in order to obtain suitable flow for film application. This work describes how the expensive and environmental hazardous volatile organic solvent content of a solvent-borne thermally cured polyester/melamine coil-coating system can be reduced by introduction of fatty acid methyl esters (FAMEs) as reactive diluents and modification of the polyester binder resin. The evaluated reactive diluents, two rape seed methyl esters (RMEs), two linseed oil methyl esters (LMEs), and a tall oil methyl ester (TOME) have been evaluated both in a fully formulated clear-coat system and via model studies. Viscosity measurements of wet paint mixtures showed that formulations with hyperbranched polyester binder hold lower viscosity than conventional polyester binder resins and that FAME works as a diluent. Fully formulated clear-coats were cured under simulated industrial coil-coating cure conditions and in a convection oven at lower temperatures respectively. FAME increases the mobility of the system enhancing the film formation process. Free-standing clear-coat films were analyzed with Raman, carbon-14 dating, extraction, dynamic mechanical analysis, and visual observation. Incorporation of FAME could not be confirmed by Raman analysis. However, carbon-14 dating indicated the presence of FAME that could not be extracted from the films. The mechanical properties of the films were also affected by the addition of FAMEs, oven temperature, choice of co-solvent, and flash-off period. Conventional film characterization tests on substrate supported coatings indicated that binder resin structure and cure conditions affect the final film properties. Model studies were performed to clarify how FAME can chemically react through transesterification with the hydroxyl-groups of the polyester. The transesterification reaction between different FAMEs and primary alcohols with and without tertiary hydrogen was monitored with 1H-NMR and real time IR. Evaporation and side reactions, e.g. alkene reactions, are competing factors to the transesterification reaction. The study showed that fatty acid structure, reaction time, and temperature affect the transesterification conversion, degree of side reactions, and choice of catalyst. A pigmented fully formulated polyester/melamine formulation with a reactive diluent was cured at full scale in an industrial coil-coating production facility. Evaluation of the final film properties showed that the coating fulfills the specification of conventional polyester/melamine coil-coating systems. / QC 20100817

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.

No description available.

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.

In this thesis, we focused on understanding the synthesis of titanium dioxide (TiO2) films and nitrogen doped TiO2 films using an atmospheric pressure Dielectric Barrier Discharge (DBD). The first part of the work was dedicated to the deposition of TiO2 films by cold plasma DBD with titanium tetraisopropoxide as precursor in a single-step process at room temperature. The deposition rate was about 70 nm·min-1. The photocatalytic degradation rate for the degradation of methylene blue (MB) under ultra violet (UV) irradiation of the TiO2 film after annealing was close to a reference anatase TiO2 spin coated film. Moreover, the TiO2 films showed a good photocatalytic stability. The second part of the study focused on the optimization and the understanding of the effect of the plasma parameters (gas flow rate and power) on the morphology of the TiO2 films and on the investigation of the deposition mechanisms. The morphology of the film changed from granular to compact film by either increasing the total flow rate or decreasing the plasma power. In other words, adapting the energy density in the plasma allowed the control of the morphology of the TiO2 films. To our knowledge, it was the first time that the energy density parameters of the plasma were used to control the morphology of TiO2 films. The photocatalytic degradation rate for the degradation of MB under UV irradiation of the annealed TiO2 film turned out to be about 2 and 15 times higher than the one of the commercial TiO2 film and the as-deposited TiO2 films, respectively. In order to extend the light utilization to the visible light range, TiO2 films were doped with nitrogen using a room temperature argon/ammonia plasma discharge. XPS and SIMS results confirmed that the nitrogen has been incorporated in the TiO2 lattice mostly in Ti-N state. This was further confirmed by Raman spectroscopy and XRD. The plasma properties and the doping mechanism were studied by Optical Emission Spectroscopy. It is suggested that the NH radicals played a key role in the doping of TiO2. The concentration of nitrogen in the N-TiO2 coatings could be tuned by adapting the ratio of NH3 in the plasma or the plasma power. The band gap of our N-TiO2 coatings is lower than the one of undoped TiO2 coating. The photocatalytic degradation rate for N-TiO2 coating was more than 4 times higher than the one of the undoped TiO2 coating. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Superalloys used in aeroengines are designed to offer superior strength at increasingly higher operating temperatures. In order to optimise the working efficiency and provide additional protection to the components such as turbine blades; a thermal barrier coating (TBC) system is applied. The TBC is a multilayer system consisting of mainly two layers i.e. bond coat (BC) and topcoat (TC). In addition, a third layer grows between the TC and BC during oxidation known as a reaction layer or thermally grown oxide (TGO). The function of the TC (usually, yttria stabilised zirconia (YSZ)) is to provide thermal insulation to aeroengine parts or reduce their surface temperatures; whereas, the BC provides binding between the TC and the substrate, and oxidation resistance to the underlying alloy by forming an adherent and continuous oxide i.e. α-Al2O3. During service, in the absence of mechanical damage to the TBC, most failures are attributed to the BC performance. The most frequently adopted BCs are; β-(Pt, Ni)Al, Pt-γ-Ni/γ’-Ni3Al and MCrAlY. In addition, reactive elements (REs) are incorporated in the BCs due to their ability to enhance oxidation resistance significantly. In the present study βNiAl based coatings/BCs and alloys with and without REs (Zr and Hf) and Pt were prepared. For the coatings CMSX-4 single crystal superalloy was used as a substrate material and pack aluminising/cementation or in-situ chemical vapour deposition (CVD) as a coating process. The isothermal oxidation testing was carried out at 1150oC for 50 and 100 hours in air. The preparation and oxidation performance of a δNi2Al3 coating was carried out, as, this is a starting material for βNiAl matrix based coatings/or BCs. The oxidation of δNi2Al3 coating showed large volumetric changes (thickness variations), multiphase TGO, TGO/coating interface melting and spallation during oxidation. In contrast, the ‘simple βNiAl’ coating (or βNiAl matrix) was found to exhibit comparably enhanced thermal stability than that of the δNi2Al3 coating. Moreover, a detailed study of the simple βNiAl coating was also carried out in order to understand the oxidation performance. The coating before oxidation in the as-deposited condition was found to contain residual compressive stresses of 140 – 200 MPa. In contrast, after oxidation analysis exhibited substantial interdiffusion between the coating and the substrate resulting in a large reduction of the Al content and influx of substrate elements into the coating. This in turn caused coating transformation from βNiAl to the γ’-Ni3Al phase and formation of a multiphase TGO (TiO2, NiAl2O4, and ϴ-Al2O3 intrusion in α-Al2O3). Moreover, the degree of the TGO spallation and residual stresses increased with the oxidation time. In order to enhance the oxidation performance of the βNiAl coatings, the substrate pre-treatment was carried out i.e. CMSX-4 superalloy was electrolytically etched to remove the γ-Ni phase and fabricate βNiAl coatings on the remaining γ’-Ni3Al. This coating is termed as E-βNiAl. In comparison to simple βNiAl, the E-βNiAl coating showed improved spallation resistance. However, E-βNiAl revealed increased surface area due to etching of the substrate and triggered fast TGO growth rates when tested in an un-polished condition. Furthermore, simple βNiAl coatings were doped with Zr and Hf separately using a two-step aluminising method. The appropriate addition of either Zr or Hf was found to reduce the substrate elements (W, Ta, Cr and Ti etc.) in the coating before and after oxidation. After oxidation, examination of the presence of Zr or Hf in the coating was found to confirm the commonly reported beneficial effects. The TGOs grown on these coatings were almost pure α-Al2O3 which subsequently reduced growth and stresses. In addition to Zr/& Hf doped coatings, a study on Hf and Zr doped βNiAl bulk alloys was also carried out in order to understand the dopant effects on the oxidation resistance of βNiAl alloys in the absence of interdiffusion (as in case of coatings). In general, the commonly reported oxidation benefits were confirmed by the addition of these elements such as reduced TGO growth, oxide pegging, a columnar morphology of the TGO and segregation of REs at alumina grain boundaries etc. In addition, two more beneficial effects are suggested to be the ‘TGO crack filling up (or crack-healing)’ and formation of the ‘dense-TGO’. Within this study, the investigation of commercially available Pt-βNiAl BC was also carried out in air and vacuum atmospheres. The results demonstrated that the initial chemistry and elemental distribution (particularly Al/& Pt) was found to affect the TGO growth and phases significantly. In addition to its well established beneficial effects, the main effect of a Pt addition is suggested to be the stabilisation of the βNiAl structure even at a lower Al content.

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

Doctor of Philosophy / Department of Chemistry / Peter M.A. Sherwood / This dissertation will examine the fabrication of different phosphorus containing films and their use as corrosion preventative films and adhesion materials between polymers and metal and metal alloys. Orthophosphate films are used in several metals and metal alloys to prevent corrosion and promote adhesion between paints or polymers and metal substrates. One key component is to examine the use of different phosphorus containing acids that might lead to phosphorus containing films which would compliment the mainly orthophosphate films currently in use. The objectives of this study are to see if it is possible to fabricate different phosphorus containing films, use them to adhere polymers to metal and metal alloys, and test the phosphorus containing films’ and polymer films’ corrosion protection properties. The thermoplastic resin, Poly(ether ketone ketone), or PEKK was found to adhere well to different phosphorus containing films and protect the underlying layers from oxidation in 4-D water. The phosphorus containing films were created by electrochemical deposition in different 5 M phosphorus containing acids. The metal or metal alloy was abraded to remove the native oxide and treated in the electrochemical cell. The second, separate polymer films were created by dip coating the metal or metal alloy in a polymer solution. The film thickness in both cases was controlled to be less than 100Å to ensure that the underlying metal or metal alloy could be detected. The surface chemical analysis was collected using X-ray photoelectron spectroscopy, or XPS. Core level and valence band XPS were used to distinguish the differences in the chemistry at the surfaces. The valence band XPS spectra were interpreted using spectra generated by multiple scattered wave calculations and band structure calculations. In the cases were more than one film was present subtraction and addition spectrum were used to interpret the chemistry in the interface region of the films.

The purpose of this study was to examine the performance of several generic types of organic protective coatings as a corrosion protection method for the interior of subsea pipelines in sour gas media. The sour gas environment was simulated in the laboratory by the use of an Autoclave and the performance of the organic coatings was studied via the use of Electrochemical Impedance Spectroscopy (EIS) and Linear Polarization Resistance (LPR) tests to determine the coatings resistance, capacitance and corrosion behavior before and after the exposure to sour gas environment. The coating degradation and the corrosion products formed were examined by the use of SEM/EDS. The results indicated that both FBE and Novolac Epoxy coatings had excellent adhesion properties and chemical resistance. The Amine-Cured Novolac Epoxy coating exhibited good adhesion properties and chemical resistance. However, the Phenolic Epoxy coating started to degrade over time and corrosion took place under the coating.