Papers by Keyword: Electrochemical Impedance Spectroscopy (EIS)

Abstract: Austenitic stainless steel 316L has been widely used in marine environment which containing sodium chloride solution (NaCl). In order to provide matching properties with parent metal, filler metal SMA 316L is commonly produced with slightly over alloyed composition. This work investigated the corrosion behavior of base metal 316L and SMA 316L weld metal by using Electrochemical Impedance Spectroscopy (EIS) to evaluate the mechanism of corrosion behavior based on impedance magnitude measurement at room temperature (27°C ). Various concentrations of sodium chloride solution i.e 1%,2%,3.5%,4% ,and 5% NaCl were prepared. Optical Metallography was also conducted to compare microstructure of base and weld metal. By using Nyquist graphs and its related equivalent circuit parameters showed that impedance magnitude of weld metal was higher which compared to base metal at any NaCl concentration. Metallography examination revealed that weld metal 316L had dendritic austenitic with delta ferrite and 316L base metal had austenite with typical twin boundaries structure. Higher chromium and nickel content in weld metal 316L was the key variable that control passive film characteristic rather than its microstructure. The lowest impedance magnitude of both 316L and all-weld metal 316L at various concentration was at 3.5% NaCl. Dissolved oxygen at 3.5% NaCl reach maximum solubility which causes severe pitting corrosion.

Abstract: The chloride permeability of concrete (UHPC) was evaluated by means of the Rapid chloride permeation test and and standard difusion test. The tests are different in the voltage applied for accelerating the transport through the concrete specimen. The permeability strongly depends on quality and curing time of the concrete.

Abstract: AbstractThis paper investigated the effect of sensitization time (0h,5h,15h,30h)on intergranular corrosion sensitivity of welded joints of Super304H stainless steel at 650°C by electrochemical impedance spectroscopy (EIS), electrochemical potentiodynamic reactivation (EPR) method and scanning electron microscopy (SEM). EPR results showed that with the increase of sensitization time, the value of reactivation rate Ra increased. Electrochmical impedance spectra of welded joint of super304H for different sensitization time exhibited the similar characteristics. The fitted results showed that the values of R_f decreased with the increase of sensitization time.

Abstract: Austenitic stainless steels are considered materials with excellent corrosion resistance, and with acceptable mechanical properties. Therefore they are recommended for various constructional, industrial and biomedical applications. However they are prone to the pitting corrosion in aggressive chloride environments. The aim of this study is to evaluate the corrosion resistance of AISI 316Ti stainless steel with nitric acid passivated surface at the temperature range 22 – 80 °C in 1M acidic chloride solution. Evaluation of the corrosion resistance is based on the results of exposition immersion tests (visual and microscopic observation of attacked surfaces, mass losses of specimens) and the results of the electrochemical impedance spectroscopy (EIS) tests.

Abstract: Crystals of the 422 symmetry class exhibit interesting piezoelectric behavior, as their piezoelectric tensor has only a single non-zero coefficient, d₁₂₃ = d₁₄: such unique behavior has the potential to enable novel gyroscopic sensors and high-precision torsional MEMS actuators. Although alpha-phase tellurium dioxide (paratellurite, alpha-TeO₂) is one of the few materials belonging to this symmetry class, this material has been primarily studied for its interesting optical properties. Indeed, a large uncertainty in the piezoelectric coefficient of paratellurite exists, with d₁₂₃ measurements on single crystals ranging from 8.13 pC/N to 14.58 pC/N; this large uncertainty results from the difficulty in using conventional piezoelectric characterization techniques on paratellurite, and impedes adoption of this extraordinary material. The present study characterizes the piezoelectric behavior of this interesting material using two independent techniques, (1) a three dimensional laser Doppler interferometer system, and (2) electrochemical impedance spectroscopy (EIS). The experimental results are analyzed using numerical simulations for dynamic excitation conditions over a frequency range of 20 Hz to 200 kHz.

Abstract: High temperature piezoelectric materials have numerous potential applications, including high temperature ultrasound NDT, MEMS, sensors, or actuators. However, conventional piezoelectric materials are unsuitable for operation above 400°C. Lithium niobate (LiNbO₃) is a promising candidate because of its very high Curie temperature (approximately 1210°C) and reasonable piezoelectric coefficients. However, the piezoelectric properties are not sufficiently understood, partly due to the difficulties in characterizing this behavior at high temperature. Degradation mechanisms well below the Curie temperature, suspected to include phase transformations, oxygen loss, and excessive ionic conductivity, further deteriorate this property. In order to better understand these physical mechanisms, electrochemical impedance spectroscopy (EIS) is used to characterize monocrystalline LiNbO₃ from room temperature to 500°C, with excitations from 20 Hz to 20 MHz. An equivalent circuit model analysis, including resonant frequencies, is developed to investigate the temperature dependence of the piezoelectric behavior, as well as the mechanical elasticity and damping. Numerical values extracted from this analysis allows for numerical simulations to model device behavior.

Abstract: The corrosion inhibition property of cucurbiturils has studied in 10% HCl for mild steel using gravimetric, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (Tafel) and scanning electron microscopy (SEM) methods. It was found that the inhibition efficiency of inhibitors increases with increase in concentration. The effect of temperature on the corrosion rate was investigated and some thermodynamic parameters were calculated. Polarization studies show that inhibitors are of mixed type in nature. The results show that they are good inhibitors, and the adsorption of inhibitors on mild steel surface obeys Langmuir adsorption isotherm. Scanning electron microscopic (SEM) studies were used to characterize the surface morphology of uninhibited and inhibited mild steel specimens. The results obtained from experimental measurements and those from theoretical calculations are in good agreement.

Abstract: By using the electrochemical methods of polarization curves and alternating-current impedance and drawing curves with Origin software as well as fitting and analyzing the data of the analytic experiments, the corrosion law of the carbon steel in stratum water containing CO₂ at different temperatures is researched in this paper. The result shows that the material corrosion in the simulated stratum water containing saturated CO₂ at different temperatures is active dissolution process and is mainly subjected to the activation control. The temperature rise increases the reaction rate of the reactant in the medium while promoting anode process and cathode process so as to increase the corrosion rate of the carbon steel. And, the auxo-action of the temperature to the cathode process is bigger than the anode process. The examples prove that the Origin software can conveniently draw the curves as well as rapidly and accurately analyze and fit the experiment data. The processing process is convenient and rapid, which can save much time than the manual calculation and works better than other professional mathematical analysis software because it does not need programming.

Abstract: The surface of porous anodic aluminum oxide (AAO) film anodizing in malonic acid, which is characterized by Scanning Electron Microscope (SEM) and ImageJ software. There are disorderly tiny pores or stripes on the first once anodizing surface. Pore diameter, pore density and porosity are decided by the first anodizing process. With anodizing step increased, pore diameter of the membrane decreased. Two-step anodization improves the order of PAA membrane greatly, which is processed on the basic of the ordered array pits at the aluminum that is observed after removing membrane of the one-step anodization. According to the experiments, porous anodic aluminum oxide (PAA) was prepared in 1.0 mol/L malonic acid, its pore diameter increased and porosity decreased with anodizing voltage increased.

Abstract: In this work the corrosion process of X52 pipeline steel in three different Mexican soils was studied. Sandy, clay and marshy soils were studied in function of moisture content. The results were related to the different stages (dry and rainy) that underground pipelines suffer during the season of the year. The electrochemical evaluations were carried out at different periods of time. The soils evaluated have different water retention and each soil has a moisture value in which the corrosion process is more active. However, this value for the marshy soil only belongs to the maximum value of moisture. The analysis of results, suggested that the corrosion phenomenon is different for each soil. The electrochemical results shown that, there was a moisture value on each type of soil that it accelerates the corrosion phenomenon. So, there is moisture content where the corrosion rate is maximum (12.7, 31.4 and 53.1 wt% H₂O, for the sandy, clay and marshy soils, respectively), obtaining values of 0.256, 0.294 and 0.383 mm/year. Furthermore, this paper propose the use of the electrochemical techniques as a complementary tool for the analysis of the cathodic protection in underground pipelines at different stages of season of the year, due to the voltage variations in different types of soils and different moisture content.