جستجوی مقالات مرتبط با کلیدواژه "corrosion behavior" در نشریات گروه "شیمی"

Zn based composite coatings reinforced with TiO2 nanoparticles were fabricated via electrodeposition with 5, 10, and 15 g/L TiO2 concentration under variant current densities of 0.08, 0.1 and 0.12 A/cm2. Field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), x-ray diffraction analysis (XRD), weight loss measurements, salt spray technique, anodic polarization, and eventually potentiodynamic polarization tests were conducted and the corresponding findings were discussed. Rising the electrodeposition current density from 0.08 to 0.12 A/cm2 for both pure Zn and Zn-TiO2 coatings led to deposit more and smaller crystals and with incorporation of TiO2 nanoparticles, the morphology changed from hexagonal crystals to flake type grains. Increasing the TiO2 concentration from 5 to 15 g/L, steadily lowered the TiO2 incorporate rate (vol.%). Accordingly, the same smoothness and even more uniformity with smaller crystallites was observed at 15 g/L compared to that of 5 g/L. Weight loss measurements, salt spray tests and anodic polarization test showed remarkable superior corrosion resistance of Zn-TiO2 (5 g/L) than that of pure Zn coating. An increas in icorr (µA/cm2) from 0.08 to 0.1 A/cm2 occurred, followed by a decrease from 0.1 to 0.12 A/cm2 for pure zinc coating. By increasing the current density from 0.08 to 0.12 A/cm2 for Zn-TiO2 coating, a steadily decrease of icorr was observed. Furthermore, by rise of TiO2 (%C) from 5 to 15 g/L, icorr experienced a significance increase that could be ascribed to the remarkable reduction in TiO2 vol.%. Ultimately, the optimum corrosion resistance belonged to the electrodeposited Zn-TiO2 (5 g/L) coating deposited 0.12 A/cm2 exhibiting the lowest amount of icorr of 2.7 µA/cm2 equal to 1.6 mpy.

In this research, the effect of PEO procedure time on the distinct properties of coatings such as morphology, chemical composition, roughness and corrosion has been studied. A scanning electron microscopy equipped with an energy dispersive spectroscopy was used to study the microstructure of the coatings. In addition, x-ray diffraction (XRD) and roughness meter were used to evaluate the chemical composition and roughness of the coatings, respectively. The corrosion properties of coatings have been also studied by polarization and electrochemical impedance experiments in the Hank's physiological solution. The results of microstructural analysis showed that rising the time of the coating procedure resulted in an increase in the size of porosity, thickness and roughness. The results of the XRD pattern showed that all coatings were composed of two phases of zirconia and zirconium titanate and that the change in time of coating did not alter the chemical composition of the coating. In the case of corrosion resistance of coatings, the most corrosion potential (611 mV) with the least corrosion current density (18.50 nA/cm2) in the coating created at the end of the third step of coating (10 minutes) resulted in the most corrosion resistance (0.602 MΩ.cm2).

In this paper, corrosion behavior of single and multilayer (TiN, CrN and TiN/CrN) deposited coatings on Ni-Cr dental alloy in artificial saliva using cathodic arc evaporation-physical vapor deposition (CAE-PVD) technique were investigated. The corrosion behavior of uncoated and coated Ni-Cr prosthetic dental alloy has been investigated electrochemically in addition to the other way represented by the quantity measurement of corrosion products which is resulted from the Ni-Cr dental alloys. Fusayama artificial saliva has been utilized as media for measuring all electrochemical behaviors. The surfaces of samples have been analyzed using X-ray diffraction (XRD), energy dispersion spectroscopy (EDS), and scanning electron microscopy (SEM). The results indicated that the coating procedure that has applied to Ni-Cr dental alloy may change wettability by decreasing the hydrophilicity of the surface. The results indicated that the strongest hydrophobic character is exhibited by CrN coating. Potentiodynamic polarization and Nyquist plots showed that CrN coating had an exceptionally high polarization resistance compared to Ni-Cr dental alloy, TiN and TiN/CrN coatings.

In this study, corrosion behavior of copper that was deformed by Simple Shear Extrusion (SSE) method was investigated in 3%wt NaCl solution. Modified Williamson-Hall method, applied on the X-ray diffraction patterns of the samples, showed that increase in the number of SSE passes led to increasing in the dislocation density in the copper samples. Moreover, such deformed samples exhibited fewer corrosion currents, in the potentiodynamic polarization test results, than that of annealed one. In addition, Electrochemical Impedance Spectroscopy (EIS) test was employed to assess the SSEed copper corrosion performance, and the results revealed that the SSE technique has a beneficial effect on the corrosion behavior of copper in 3 wt% NaCl aquatic solution.

Nanostructure multilayer alloy coatings (NMAC) of Co-Ni were developed on copper in layered manner using different current pulses. NMAC of Co-Ni was deposited galvaostatically from acid sulphate bath under different combination of cyclic cathode current densities (CCCD’s) and number of layers. Corrosion behaviors of coatings were evaluated in 1 M hydrochloric acid, as representative corrosion medium. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) study revealed that NMAC (Co-Ni) 2.0/4.0/6.0/60/three exhibits~160 times better corrosion resistance than monolayer coating, deposited from same bath for same time. Better corrosion protection was attributed to the increased effect of interface, arising from the exceptional thinness of the layers. As composition of alloys in successive layers were varied, consequent to the deposition current density (c.d.), the change in phase structure of the deposits were observed, confirmed by X-ray diffraction (XRD) study. Layer formation and surface after corrosion tests were examined by scanning electron microscopy (SEM) and optical profilometer, and reasons responsible for better protection were analyzed.

Zn-Co, Zn-Fe and Zn-Co-Fe coatings were electrodeposited on mild steel from an acid sulphate bath, using thiamine hydrochloride (THC) and citric acid (CA) as additives. Bath constituents and operating parameters were optimized by standard Hull cell method, for peak performance of the coatings against corrosion. The effect of current density (c.d.), pH on the deposit characters, such as corrosion resistance, hardness, thickness, partial current density and CCE were studied and discussed. Corrosion resistances were evaluated by Potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) method. Corrosion resistance of the Zn-Co-Fe coating under optimal c.d. (3.0 A dm-2) was found due to its inherent high dielectric barrier, evidenced impedance signals. High partial current density for zinc in Zn-Co-Fe alloy coating supports the possibility of a synergistic catalytic effect of Co on Fe and vice versa. X-ray diffraction study clearly indicates that a drastic change in corrosion resistance of ternary alloy is due to the change in the phase structure of the coatings, compared to binary alloys. Surface morphology and composition of the coatings were examined by using Scanning Electron Microscopy (SEM), interfaced with Energy Dispersive X-ray Analysis (EDXA) facility, respectively.