Papers by Keyword: Corrosion

Abstract: Multi-functional thin films have gained increasing importance in a decorative application. Among the available material, titanium nitride (TiN) thin film is interesting due to its golden color and mechanical resistance. Beside their properties, the corrosion property of TiN films is mainly considered in order to extend the life time. In this work, the TiN thin films were deposited on 3x3 cm² Si(100) substrates by dc reactive magnetron sputtering technique. The effects of N₂ partial pressure (P_N2) on deposited film properties such as microstructure, surface morphology, color, mechanical and corrosion properties were investigated. We found that the crystal structure of the TiN films exhibit the (200) preferred orientation. The color of TiN films change from gold-yellow to gold-red colors by increasing of N₂ partial pressure that could be explained by Drude model. The TiN films have smoother surface when the N₂ partial pressure increases. Standard corrosion tests in artificial sweat solution show the corrosion current density (i_corr) in the range between 0.25 to 4.25 mA/cm² and the polarization resistance increases with increasing of N₂ partial pressure. The highest hardness of the film is approximately 40 GPa with elastic modulus of 340 GPa. We conclude that N₂ partial pressure corelates with color, mechanical property and corrosion resistance of TiN films, which were optimized to use in decorative application.

Abstract: In this study, we investigate a facet of the fabrication process of chromium nitride (CrN) film intended as a protective coating for pineapple blades. CrN thin films were deposited on unpolished stainless steel substrates (AISI304) by DC reactive magnetron sputtering in Ar+N₂ gases. In principle, the proportion of nitrogen partial pressure to the total pressure in the sputtering process should have considerable effects on the CrN film’s chemical composition, its crystal structure, its hardness, and its corrosion resistance. We tested this supposition out by using several different nitrogen partial pressures in the sputtering process and observed the films deposited. The coatings were deposited at five different nitrogen partial pressures of 4.0x10^-4 mbar, 8.0x10^-4 mbar, 1.2x10^-3 mbar, 1.6x10^-3 mbar, and 2.0x10^-3. The deposition times were controlled to achieve 5-µm thick films in each deposition. The films were analyzed by several analytical methods, such as X-ray diffraction (XRD), scanning electron microscope, micro-hardness and potentiostat in pineapple juice. The XRD spectra of the films showed face-centered cubic structure with (200) preferred orientation, positively identifying them as Cr₂N and CrN thin films. The calculated d-spacing and lattice parameter of the CrN films increased with increasing nitrogen partial pressure; the ranges were 0.283–0.287 nm and 0.491-0.497 nm, respectively. The cross-section morphology of the CrN films reveals the columnar grain growth with a high density. The crystal structure and the grain texture correspond with the hardness property. The films corrosion potential, an indicator of their corrosion property, was varied from -0.14 to -0.05 volts with varying nitrogen pressure. The most corrosion resistant and the good hardness were the film fabricated at the nitrogen partial pressure of 1.2x10^-3 mbar.

Abstract: Acoustic emission (AE) is a non-destructive technique which is well known for crack monitoring. Moreover, it has been widely used for corrosion and erosion damage on metallic structures. In this study, AE technique was applied for quick monitoring of corrosion resistance of lacquer coatings on tin free steel and laminated steel for food can-packaging. There were three types of coatings: (A) BPA-NI lacquer, (B) BPA-complied lacquer, and (C) PET lamination. These coatings were investigated in flat-sheet and in deformed sheet. Cathodic disbonding (CD) technique was carried out to cause separation between the coating and the metal substrate and initialize corrosion damage. AE signals was detected immediately with potential excitation, and showed good correlation with coating corrosion resistance during corrosion development. AE count signal matched with resulting current during CD, and proportional to corroded areas. In addition, coatings properties were measured before and after the CD process by electrochemical impedance spectroscopy (EIS). A combination of AE and CD techniques offers an in-situ non-destructive corrosion monitoring of coating quality before and during delamination development, and useful for can-packaging testing.

Abstract: The coupling between mechanical and chemical behaviors is investigated. The Generalized Eigenstrain Method is used and enables to take easily into account several couplings, such as damage and corrosion. Modeling is then performed and compared for different configurations. Chemical reactions and diffusion effects are thus described in order to improve accuracy of such a micromechanical time-dependent model. Application is then performed on a steel reinforced concrete material. Moreover, a particular and original coupling has been introduced, which is justified by thermodynamics arguments.

Abstract: The paper describes static failures, reconstruction and redevelopment of reinforced concrete load-carrying structures in the Municipal Bath House in Moravská Ostrava. The building was built at the beginning of the 1960s.The architectural, structural and typological features are typical of that time. Several rather serious failures have occurred during the operation in the reinforced concreted load-carrying skeleton and the bath tub structure. Reasons for the failures and general degradation of some parts of the reinforced concrete included undermining, weather, leakage of aggressive water and vapour from baths, saunas, laundry and other facilities. This paper describes the static underpinning, improvement of the degraded reinforced concrete structures and technical aspects of transformation of a former civil defence shelter into a wellness and swimming centre.

Abstract: Based on nanometer related theory, this paper has used H68 alloy for power plant condensers alloy surface nano mechanical polishing method, combining the related theory of materials research, the use of metallographic microscopic analysis, XRD analysis, hardness test and electrochemical corrosion test method, the correlation properties of nano surface treatment of H68 test, around the related properties of nano surface treatment H68 experiment, theoretical analysis and normative analysis, combining qualitative analysis with quantitative analysis, it has concluded that the surface nano can improve the corrosion resistance of H68 alloy in ammonia solution.

Abstract: The corrosion behavior of pipeline steel containing 1%Cr is studied by using immersion experiment. The corrosion rust is characteried with macroscopic/microscopic surface morphology, corrosion kinetics and corrosion phases. The results demonstrate that the main corrosion products are lepidocrocite and goethite, Cr-rich compound consists of the inner layer. The corrosion process could be divided into three stages. At stage 1, the corrosion rate decreases fast, and the distributed corrosion products are formed. At stage 2, the granular corrosion products appear on coupons surface gradually, and a plain corrosion rate is obtained. At stage 3, a compact and dense corrosion layer attaches to coupons surface, and corrosion rate decreases mildly.

Abstract: Magnesium alloy as a green material in the 21st century, because of its excellent physical and mechanical properties of metallic materials as an ideal in the automotive industry, electronic industry and aviation, aerospace and other industries^[1]. However, poor corrosion resistance of magnesium alloys become an important issue hinder application of magnesium alloys^[2]. So magnesium alloy corrosion problems and the current status of research paper reviews several magnesium alloy protection methods at home and abroad, and also highlighted with our latest laser shock (LSP) study of AZ91 magnesium alloy at high strain rates of corrosion resistance results.

Abstract: We chose cast and extrude magnesium alloy AZ61 as materials and studied the influences of temperature, humidity, pressure and NaCl atmosphere on the corrosion products and corrosion mechanism by means of SEM, EDS and XRD. we could indicate the corr osion rate of extruded AZ61 magnesium is faster than that of cast AZ61 magnesium. Both th e rearrange of second ph ase and smaller grain size, which owing to the extrusion process, change the morphologies of corrosion products.

Abstract: In the present study, a thick, uniform and crack-free sol-gel coating embedded with Al₂O₃-CeO₂ nanoparticles was successfully synthesized and deposited on aluminum alloy AA6061 by spin coating method. The coating morphology was characterized by using a scanning electron microscopy coupled with electron diffraction x-ray spectrometer (SEM-EDX), an atomic force microscopy (AFM) and water contact angle measurements. FT-IR spectra were obtained using a Fourier transformation infrared spectrometer. The corrosion resistance of this coating in 3.5 wt.% NaCl solution was evaluated with electrochemical methods including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The stability of the corrosion resistance of this coating was evaluated by immersion in 3.5 wt.% NaCl solution and by exposure to the UV radiation condition. In addition, the adhesion resistance of the coating was also assessed. SEM and AFM results showed that Al₂O₃-CeO₂ nanoparticles dispersed uniformly in the room temperature vulcanized (RTV) silicon rubber matrix and formed a thick and crack-free coating. Both polarization and impedance results reveal that CeO₂-Al₂O₃ nanoparticles embedded silicon rubber coating can improve the corrosion resistance of the AA6061 alloy by more than three orders of magnitude. Meanwhile, the corrosion resistance of this coating was found to be stable under immersion in 3.5 wt.% NaCl solution and UV exposure conditions. However, excessive content of CeO₂ nanoparticles in the coating made the coating morphology porous and decreased the thickness of the coating, which resulted in the decrease in the corrosion resistance of the coating.