الفهرس 
. Introduction and literature reviewOnly 14 pages are availabe for public view
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Abstract
Different methods may be applied to separate the metal’s surface from destructive environments and preserve its outer exposed area, including corrosion inhibitors, alloy structures, or coating techniques. Although metal coating with protective layers has become a cost-effective technique, it is the most effective path to corrosion easement. Although metal coating with protective layers has become a cost-effective technique, it is the most effective path to corrosion easement. Meanwhile, another important factor, water composition, is very effective in the accelerating corrosion, such as the salinity of natural seawater simulated in a 3.5% NaCl solution was applied due to its high corrosive effect on metals. It was commonplace to use sodium chloride solutions. One of the major compounds is silicon compounds. The choice of SiC, silicon or silicon dioxide is related to its excellent characteristics in corrosion reduction. The excellent characteristics of SiC include high thermal stability, electronic and unique optical characteristics, long age without any damage, and good mechanical strength and hardness.
The first study in the present thesis is a novel fabrication process of SCDNTs (SCDNTs) by a solid state reaction pathway of silicon-carbon (MSCinachyrella sp.) resources. The synthesis process was proceeded by using a trimetal oxides catalyst (Fe/Ni/Zr) supported on different Al2O3 substrate (95%-50%-20%-10%). The synthesis of SiC was optimized by different factors, including reaction temperature, reaction atmosphere, reaction time, and finally sponge mass. By increasing the pyrolysis temperature to 900 °C, two target products are; SiC and polycrystalline SiO2, with two minor products being; silicon and carbon nanotubes. With further heating to 1050°C and 1200°C, the composite yield was increased to 80% at 1200ºC and a great crystallinity degree of 81%. At 1200ºC, when the heat treatment time was increased, that was divided into two stages of pyrolysis: one was under nitrogen for (0 or 2h), and the second was under argon flow (2, or 4h) at a fixed heating temperature of 1200 °C, the final yield formed from the pyrolysis increased significantly from 50% to 90% g. Another factor is percent of Al2O3, when the aluminum powders were minor or major, the residues were amorphous. Only when the aluminum powders were suitable (50%), the composite of SiO2 and SiC was more readily fabricated. from the transmission electron microscope (TEM), the pyrolysis reaction yielded multiple kinds of nanostructures connected with each other, forming a skeleton-like structure. The tube-like nanostructures of polycrystalline SiO2 dominate-SiC-silicon dioxide nanotubes, and their length extends to micrometers. Besides the nanotubes, two different structures of SiC embedded into the silicon dioxide tubes; all of these structures formed were skeleton-like.
The second part is to fabricate different layers (1-5) of SCDNTs coating on the surface of steel by spin coating techniques and studying of its corrosion inhibition in 3.5% NaCl. The corrosion inhibition was studied using potentiodynamic polarization and electrochemical impedance. from potentiodynamic polarization, it was obvious that the corrosion current density (icorr) of steel decreases rapidly due to the presence of a nanocomposite SCDNTs thin film on the surface of the steel, indicating that the coat inhibits the corrosion of steel. Further, the corrosion current density was gradually diminished with the parallel increase in the number of the coating layers as a result of increased protection from the nanocomposite SCDNTs thin films. The value of the Ecorr changed to a more positive potential in the presence of a coat, revealing that nanocomposite SCDNTs thin films act mainly as an anodic type. Furthermore, non-destructive EIS measurements illustrated the Nyquist and Bode curves for uncoated (blank) and coated steel samples. The Nyquist diameter of the semicircles enhanced with increasing the fabricated layers, indicating an improvement in IE %. In Bode plots, it was seen that the impedance of SCDNTs thin layers rises with increasing the layers from 1 to 5-layers during the corrosion process. The inhibition efficiencies of the SCDNTs on steel calculated from Tafel plots are in good agreement with those obtained from EIS measurements. After 80 h of immersion time, the coated surfaces of steel were characterized by XRD spectra, SEM, TEM, AFM, and streomicroscope. All analyses approved the excellent contact and hardness of SCDNTs thin layers on the surface of steel and the nearly light difference in the structure and morphology before and after corrosion treatment.
The third part is to fabricate a conducting polymer of cellulose acetate-poly acrylonitrile with SiC ((CAPA)–SiC composite) by an in situ chemical oxidative polymerization method in an aqueous medium. Both the structure and morphology of the CAPA–SiC composite were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Surface area studies (BET) and surface morphology (SEM&TEM) that approve confirmed the presence of each constituent in the compact structure. Subsequently, the synthesized CAPA–SiC composite was introduced to commercial epoxy paint through a casting method, and the three-component CAPA– SiC/paint materials were applied onto the surface of copper. The corrosion resistance of the CAPA – SiC/epoxy paint coating was evaluated by Tafel polarization and electrochemical impedance spectroscopy measurements in a 3.5 wt% NaCl solution and also compared with that of a CAPA/paint coating. The excellent corrosion protection ability of the CAPA–SiC/epoxy coating is mainly achieved with percent 97.4%. The coating on the copper surface was characterized via XRD and SEM that which approved the still presence of all composite peaks and nearly no change in the morphology of the surface.