Papers by Keyword: Electrochemical Technique

Abstract: This paper deals with the basic theory and the usability of Scanning Electrochemical Microscopy (SECM) in corrosion research. The SECM is the in situ method of surface characterization which is based on the scanning of the tested surface using ultramicroelectrode and simultaneous electrochemical testing of the surface. This technique provides an electrochemical imaging of the surface. Key applications of SECM have been demonstrated based on the newest literature data covering the past two years of the active research in the field of corrosion in a nanoscale.

Abstract: Copper (II) palmitate complex was synthesized using an electrochemical technique in the presence of palm-based palmitic acid as the ligand and Cu (II) ions from the slow released of anode material through the electrochemical oxidation of Cu foil. The system consisted of Cu foil and a graphite rod as the anode and cathode, respectively, while ammonium acetate was used as a supporting electrolyte. X-ray diffraction and spectroscopic studies were carried out to characterize the synthesized complexes using powder XRD, XPS, FTIR and UV-Vis. The results obtained showed that the desired Cu (II)Pa complex was successfully synthesized using the electrochemical technique. The surface morphology of the complexes was analyzed using FESEM, and the micrograph obtained showed that the synthesized complexes formed nanosized matchstick-like structures. This conclusion is supported by the TEM micrograph which shows the presence of nanoparticles with different diameter ranges from 2 to 3 nm.

Abstract: Present paper reports investigations carried on corrosion behaviour of mild steel in effluents collected from paper mill treatment plant. For this purpose, effluent was collected from after primary and secondary treatment stages. Mild steel samples were exposed to these effluents for duration of six months. The corroded samples were analysed for weight loss and extent of localised corrosion. Electrochemical polarization tests like open circuit potential (OCP), tafel plot and anodic polarization were also performed to estimate corrosion rate, polarization resistance and localized corrosion parameters in the studied system. The extent of corrosion attack has been correlated with effluent parameters namely pH, electrical conductivity (Ec), total suspended solids, total dissolved solids, chemical oxygen demand, biochemical oxygen demand, chloride content, colour and sulphate.

Abstract: Chemical and electrochemical techniques were applied to evaluate the porosity of various electroless coatings (single-layer coating, multilayer coating and ternary coating). The electrochemical techniques include linear polarization resistance and Tafel extrapolation method. The effects of these techniques were compared. It’s evident that electrochemical methods performed better than chemical method when they were applied to assess the porosities of coatings with very fine through pores.

Abstract: The main objective of this project was to study the corrosion rate of three different structured packing materials, a metallic, one polymeric and the other one ceramic, which will be in contact with an aqueous solution of MEA (monoethanolamine) to 30% and sour gases in a countercurrent absorption column. The materials were studied in two electrochemical cells: the first one in the presence of an aqueous solution of 1N sulfuric acid, and the second in the aqueous solution of MEA 30%, the study was done using the Tafel extrapolation methods and resistance to the polarization to measure the corrosion current (I Corr), and determine the corrosion rates of the three materials structured packings. The standard procedure used was according to ASTM G59-91, following the technique ININ No. P. SC (Cl) -06, the following results were found: in the presence of 1N sulfuric acid solution the metallic material presented a rate of 7.8 x 10-4 corrosion mpy (miles per year), the polymeric material submitted a corrosion rate of 2.82 x 10-4 mpy, and the ceramic material presented a corrosion rate of 1.03 x 101 mpy. With the aqueous solution of MEA at 30% in weight, and the sour gases the results were as follows: the metallic material presented a corrosion rate of 6.42 x 10-2 mpy, the polymeric material submitted a corrosion rate of 1.48 x 10-1 mpy and the ceramic material presented a corrosion rate of 5.6 x 10-1 mpy. These results provide a basis for predicting the lifetime of the three materials, as well as chemical resistance in the absorption column. Finally, we examined the morphology of the etched surface by scanning electron microscopy and found that in the metallic material was formed a layer of Cr2O3, which is helping the passivating material to further protect the acid attacks, the polymer material has a surface smoother after the attack and in the ceramic is observed pores larger than those observed in the material before the attack.

Abstract: The study of calcium carbonate adsorption is important significance to understand the fouling mechanism that is a major component of heat exchanger fouling. The influence on the adsorption of CaCO₃ crystallization fouling was researched in different material, roughness and supersaturation by the electrochemical impedance-time method. The results show that the material is not the essential influence on CaCO₃ absorption by analyzing the CaCO₃ adsorption layer data. The optimum conditions of maximum adsorption CaCO₃ quality: the roughness of the electrode polished by the sandpaper of 360 mesh, the supersaturation of 0.291g / L CaCO₃ solution. The experimental results of supersaturation are concordant with the roughness experiments. When the supersaturation is the middle value, the maximum adhesive force can reach the maximum. So the regulation of calcium carbonate supersaturation and roughness of heattransfer equipment can prevent the fouling. This study is a powerful detecting method to research the influence of the roughness on the adsorption of CaCO₃ crystallization fouling.

Abstract: This paper researches the effect of the interfacial transition zone (ITZ) on the migration behavior of cations under the Accelerated Lithium Migration Technique (ALMT). Cylindrical mortars with different aggregate volume fractions (V_f) and w/c=0.5 were used. The result shows that when V_f ≤ 20 %, the Li⁺ steady state migration coefficient (D_s) is influenced by the dilution and tortuosity effects of the aggregate. The combined effect of ITZ and percolation occurs at V_f = 30 %, and the effects increase with the increase in V_f. Based on the experimental and regression analysis results, when the assumed thickness of ITZ = 20 μm, the approximate D_s of ITZ and percolated ITZ are 46.4 and 52.6 times the matrix migration coefficient.

Abstract: This study utilizes mortar specimens, to design 3 different a/c ratios of 2.25, 2.75, and 3.25. The aggregate volume ratios (V_f) are 46 %, 52 %, and 57 %, respectively, while the w/c ratio is 0.5, and undergoing a 9, 12, and 15 A/m2 constant current density Accelerated Lithium Migration Technique after curing for 3 months. Results show that, on specimens applied with the same current density, the time of Li⁺ to pass through the specimen, and steady state flux and migration coefficient all exhibit a positive linear correlation with V_f. At the same time, the non-steady state migration coefficient for Li⁺ have a negative linear correlation with V_f.

Abstract: The corrosion behavior of CuCr, CuZr and CuCrZr alloys in NaCl solution is reported in this paper. The corrosion performance has been evaluated in NaCl solution atmosphere. The results show the corrosion resistance of pure copper decrease with the addition of the alloying elements initially. However, in the later exposure stages, the corrosion resistance of CuZr and CuCrZr alloy deteriorates significantly while the corrosion resistance of CuCr alloy is slightly better than that of pure copper. In addition, the results of the electrochemical experiments indicate that the different behavior for the element Cr and Zr in the base material and corrosion scales lead to the change of the corrosion resistance.

Abstract: In this study, an Accelerated Lithium Migration Technique (ALMT) was applied to simultaneously drive alkali out and lithium into concrete as a remedy for alkali-silica reaction (ASR) problem. The mortar specimens used in the experiments contained 2.0% Na2Oeq. Constant current denities were applied during the ALMT testing process. The anolyte and catholyte solutions consisted of LiOH．H2O and Ca(OH)2, respectively. The results show that there are a well correlated linear relationship between the applied current density and the steady flux and migration coefficient of the Li+. During the process of ionic migration, K+ was first removed completely from the specimen, followed by Na+, after which the Li+ flux remained steady. The system resistance initially decreased, and then increased gradually. The time corresponding to when the Li+ concentration in the cathode/Li+ in the source cell was equal to 0.1% indicates the time-span needed for Li+ to penetrate throughout the specimen. Furthermore, the accumulated charge carried by the cations and the accumulated charge applied during testing showed a similar in all test cases.