Potential Sweep Rate Research Articles

ELECTRO RECOVERY OF TELLURUM IONS FROM NON-AQUEOUS N-N DIMETHYLFORMAMIDE ELECTROLYTE

The work presents studies of the mechanism of recovery of tellurium ions from non-aqueous N-N dimethylformamide. For this, linear and cyclic current-voltage polarization curves have been recorded. The influence on the process of the concentration of tellurium ions, change of potential sweep rate and temperature has been investigated. By recording linear polarization curves, it has been established that the reducing process of tellurium ions is controlled by their diffusion to the cathode surface. The influence of the concentration of its ions in the electrolyte, the rate of change of the potential and the temperature on the tellurium deposition process was studied. By recording the cyclic polarization curve, the potential area where tellurium ions precipitate and its anodic dissolution occurs is determined. It was determined that the increase in the concentration of tellurium ions and the temperature increases the speed of the reduction process of tellurium, and the reduction process itself is controlled by the diffusion of tellurium ions on the cathode surface. To confirm the obtained data, polarization curves have been recorded on a rotating platinum disk electrode. Data received, exactly the linear dependence of ip on the electrode rotation speed (ω) to the power of 0.5, confirms that, that the process of reduction of tellurium electrodes in non-aqueous N-N dimethylformamide is controlled by diffusion polarization

Is the Interfacial Electrochemical Behavior of Quercetin the Same as That of Catechol Plus Resorcinol?

Background: Electrodeposition of functional films from polyphenol-containing solutions has emerged as a new field of surface functionalization from bio-sourced molecules. There is, however, almost no knowledge about the chemical structure of such complex films. It is the aim of this research to use the known electrodeposition of films made from catechol and resorcinol, two isomers of dihydroxybenzene, to understand the electrodeposition of a more complex polyphenol, quercetin, which is constituted from a fused catechol and resorcinol moiety. The aim of this article is hence to introduce some methodology in the interpretation of the electrochemical behavior of complex polyphenols starting from their building blocks. Methods: Cyclic voltammetry (CV) is used to deposit films from quercetin and from equimolar blends of catechol and resorcinol on amorphous carbon and gold working electrodes. The main experimental parameter was the potential sweep rate used during the CVs. Results: The CV of quercetin is not the exact sum of the CV of the catechol + resorcinol blends, but the major features are conserved, namely the presence of two main oxidation peaks affiliated to those of catechol and resorcinol but shifted to less anodic potentials. In addition, the anodic electron transfer coefficients of the two oxidation waves of quercetin are higher than those measured in the catechol resorcinol blend. However, film deposition ability is reduced with quercetin compared to catechol + resorcinol blend in probable relationship to steric hindrance occurring during the non-electrochemical crosslinking of the deposit. The quercetin-based films deposited at 10 mV·s−1 on gold electrodes are conformal and display some antioxidant activity.

Cobalt ferrite (CoFe2O4)–activated carbon fabric (ACF) based composite electrode material for supercapacitor application

In the present article, rayon based activated carbon fiber/fabric (ACF) has been developed and explored as an active electrode material in combination with metal oxide for ultracapacitor application. Herein, the ACF is derived from rayon-based carbon fabric through activation and carbonization processes in a tubular furnace and prepared composite material of cobalt ferrite (CoFe2O4, Cof) and activated carbon fabric/fiber. The ACF, cobalt ferrite, and electrode material derived thereof are analyzed by FTIR, XPS, BET surface area analyzer, and XRD methods. The surface morphology and composition of prepared composite is examined by FESEM and EDX. The electrochemical properties of Cof-ACF composite are scrutinized by cyclic voltammetry. The composite material produces considerably high electrochemical supercapacitances in the order of 1287 F/g and 788 F/g at a potential sweep rate of 2 mV/s in 0.5 M phosphoric acid and 0.5 M sulphuric acid electrolytes, respectively. The electrochemical behavior of the cobalt ferrite decorated ACF electrode material exhibits a slightly higher energy density (176.98 Wh/kg) in H3PO4 than in H2SO4 (150.79 Wh/kg) electrolyte. The stability (~74 %) of electrode materials is retained even after 3500 cycles of charge/discharge in acid electrolytes. Thus, Cof-ACF composite material could be used as a cost-effective, compact, and light-weight electrode material with enhanced stability and improved performance for ultracapacitor and energy storage device applications in acid electrolytes.

Influence of alkaline earth metals on the corrosion-electrochemical behavior of lead babbit BKa, BSt, BBa (PbSb15Sn10) in NaCl electrolyte medium

The article presents the results of study of the effect of additions of calcium, strontium and barium (0.01–1.0 wt %) as a structure modifier on the anodic behavior of lead babbits BKa, BSt, BBa (PbSb15Sn10) in NaCl electrolyte medium. The studies were carried out by the potentiostatic method in a potentiodynamic mode with a potential sweep rate of 2 mV/s.Studies show that with time the free corrosion potential of alloys shifts to the positive side, and with an increase in the concentration of the modifier (calcium, strontium and barium) in lead babbits, acquires a positive value. The addition of calcium to lead babbit BKa (PbSb15Sn10Ca) increases its corrosion resistance by 10 – 15%, strontium BST (PbSb15Sn10Sr) by 15–20%, and barium BBa (PbSb15Sn10Ba) by 20–25%. An increase in the corrosion rate of alloys was noted, regardless of t heir composition from the NaCl concentration in the solution. It has been shown that an increase in the chloride ion concentration in the NaCl electrolyte leads to a decrease in the potentials of free corrosion, repassivation, and pitting formation of alloys.

Effect of lithium on the anodic behavior of AlTi0.1 aluminum conducting alloy in NaCl electrolyte environment

Aluminum ranks as the fourth most conductive metal, trailing behind silver, copper, and gold in electrical conductivity. Annealed aluminum demonstrates an approximate 62 % conductivity of the International IACS compared to annealed standard copper, which registers 100 % IACS at t = 20 °C. Because to its low specific gravity, aluminum exhibits twice the conductivity per unit mass compared to copper, showcasing its potential economic advantage as a material for conducting electricity. For equal conductivity (in terms of length), an aluminum conductor exhibits a cross-sectional area 60 % larger than that of copper, while weighing only 48 % of copper's mass. However, the widespread use of aluminum as a conductor in electrical engineering is often challenging and sometimes unfeasible due to its inherent low mechanical strength. Enhancing this crucial property is achievable through the addition of dopants. However, this approach tends to elevate mechanical strength at the cost of noticeable reductions in electrical conductivity. This study investigates the impact of lithium addition on the anodic behavior of an A5 aluminum conductor alloy, specifically modified with 0.1 wt.% Ti (AlTi0.1 alloy), within a NaCl electrolyte environment. The experiments were conducted utilizing the potentiostatic method in potentiodynamic mode at a potential sweep rate of 2 mV/s. Results indicate that the introduction of lithium to the AlTi0.1 alloy leads to a shift in the potentials of free corrosion, pitting, and repassivation towards positive values. Additionally, the corrosion rate decreases by 10–20 % with the incorporation of 0.01–0.50 wt.% Li. Moreover, varying concentrations of chloride ions in the NaCl electrolyte prompt fluctuations in the corrosion rate of the alloys and a shift in electrochemical potentials towards the negative range.

Анодное поведение свинцового баббита БСт (PbSb15Sn10Sr), модифицированного стронцием, в среде электролита NaCl

The article presents the results of a study of the effect of strontium additives (0.01 – 1.0 wt. %) as a structure modifier on the anodic behavior of lead babbit (PbSb15Sn10Sr) in the NaCl electrolyte medium. The studies were carried out by the potentiostatic method in the potentiodynamic mode with a potential sweep rate of 2 mV/s. Studies have shown that over time, the free corrosion potential of alloys shifts to the positive side and with an increase in the concentration of the modifier (strontium) in lead babbit, it acquires a positive value. The addition of strontium to lead babbitt (PbSb15Sn10Sr) increases its corrosion resistance by 10 – 15 %. An increase in the corrosion rate of alloys was noted, regardless of their composition from the NaCl concentration in the solution. Studies have shown that an increase in the concentration of the chloride ion in the NaCl electrolyte leads to a decrease in the potentials of free corrosion, repassivation, and pitting of alloys.

Temperature Dependent Operando High Energy Surface X-Ray Diffraction Studies of Pt(111) Oxidation

Platinum electrocatalysts are still widely used as cathode material in proton-exchange membrane fuel cells (PEMFC) because of their high ORR activity. However, their long-term stability is limited due to degradation processes. This degradation is partly caused by Pt oxidation and oxide reduction, which lead to irreversible surface restructuring and subsequently Pt dissolution. To increase the lifetime of PEMFCs it is mandatory to understand the mechanisms behind the degradation on an atomistic level. This requires studies by structure sensitive in situ methods, in particular, also studies at the elevated temperatures typically employed in PEMFCs operation.Previous studies revealed that in the initial stage of oxide formation Pt atoms are extracted out of the surface and form an ultra-thin oxide layer directly above the surface. This extraction is long known as place exchange [1], but the atomic-scale details of the surface oxide structure, the extraction mechanism, and especially the kinetics of the initial oxide growth were only recently clarified [2-7]. It was found that the structural arrangement of the Pt atoms within the surface oxide on the Pt(111) and the Pt(100) surface is distinctly different, leading to differences in the oxidation/reduction kinetics, the reversibility of the surface oxidation/reduction process, and the amount of Pt dissolution into the electrolyte.Recently, we performed fast operando high-energy surface X-ray diffraction (HESXRD) studies, in which we investigated the initial extraction of Pt atoms on Pt(111) during potential cycles. Surprisingly, it was found that the Pt extraction during the anodic sweep is largely independent of the potential sweep rate, although the peak cyclic voltammograms (CVs) associated with the charge transfer during surface oxidation showed a pronounced shift [7-9]. This suggests that the Pt extraction is a fast process, rather driven by potential and not directly coupled to the slow formation of surface oxygen species. However, the Pt extraction during the anodic sweep and the re-insertion during the cathodic sweep still exhibit significant hysteresis, indicating a complex multistep oxidation kinetics.Previous electrochemical studies of Pt(111) electrodes revealed that the described influence of oxidation/reduction kinetics and the reversibility of the charge transfer processes increase at elevated temperature [10]. However, the temperature dependence of the Pt extraction behavior is currently unknown, because all previous structural studies of oxide growth and reduction have been performed exclusively at room temperature.For the experiments at elevated temperatures we developed a new setup for HESXRD studies of single crystals, which combines a hanging meniscus electrochemical cell for operando X-ray diffraction measurements with an inductive heating device in a joint Ar-filled compartment. This setup allows direct (re-)preparation of the aligned Pt single crystals on the diffractometer. By this, the time between preparation and measurement is reduced down to a few minutes and sample transfer through air is rigorously avoided.Temperature-dependent HESXRD measurements at temperatures up to 343 K were performed at beamline ID31 of the European Synchrotron Radiation Facility. The simultaneously measured electrochemical current and X-ray intensity indicate kinetic shifts in the charge transfer but a rather temperature independent Pt extraction process.We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft via project no. 418603497 and the BMBF via 05K19FK3 and 05K22FK1.

Effect of Barium on the Corrosion and Electrochemical Behavior of Lead Babbit BBa (PbSb15Sn10Ba) in a NaCl Electrolyte Medium

Results are presented from studying the effect barium additives (0.01–1.0 wt %) as a structure modifier have on the anodic behavior of lead babbit BBa (PbSb15Sn10Ba) in a NaCl electrolyte medium. The studies are performed using the potentiostatic technique in the potentiodynamic mode with a potential sweep rate of 2 mV/s. It is shown that the free corrosion potential of alloys shifts to the positive side over time and acquires a positive value upon an increase in the concentration of the modifier (barium) in the lead babbit. Adding barium to lead babbit BBa (PbSb15Sn10Ba) raises its corrosion resistance by 20–25%. An increase in the rate of the corrosion of alloys is noted, regardless of their composition and the concentration of NaCl in a solution. It is shown that raising the concentration of chloride ions in a NaCl electrolyte lowers the potentials of the free corrosion, repassivation, and pitting of alloys.

Cathodic Polarization Behavior of Steel in Aqueous MgCl2 Solutions Containing Zn2+

So far, we have revealed that the dissolution rate of zinc is accelerated in relative high concentrations of MgCl2 in the corrosion process of galvanic couples consisting of zinc and steel. In this study, we investigated the cathodic polarization behavior of steel in MgCl2 solution containing Zn2+ and the effect of Zn2+ dissolved in the solution on the oxygen reduction reaction and hydrogen evolution reaction.The specimens used in the experiments were carbon steel SS400 (Fe-0.12C-0.60Mn-0.011P-0.019S) machined into a 1.5×1.5×0.3 cm3. One side of the specimen was polished with SiC abrasive paper up to #2000 grit and degreased in acetone before being used for the experiment. The test solution was mixtures of 0.25 M MgCl2 + x mM ZnCl2 (x = 2.5, 5 mM, Mg/Zn molar ratio: 100, 50) at room temperature under a naturally aerated condition. As a comparison solution, 0.5 M NaCl + y mM ZnCl2 (x = 5, 10 mM, molar ratio of Na/Zn: 100, 50) with the same chloride ion concentrations were used. Cathodic polarization curves of steel were measured using a three-electrode method with a platinum wire as the counter electrode and an Ag/AgCl electrode (saturated KCl, SSE) as the reference electrode. The potential sweep rate was 0.5 mV/s. After the polarization test, the specimen surfaces were observed with a scanning electron microscope and analyzed for corrosion products formed during cathodic polarization with XRD and laser Raman spectroscopy.The cathodic polarization behavior of steel in MgCl2 solution without Zn2+ was investigated and compared with that of NaCl solution without Zn2+. Diffusion-limited currents of dissolved oxygen reduction (ORR) were observed at -0.6 V to -0.8 V in MgCl2 and NaCl solutions. Furthermore, cathodic polarization in MgCl2 and NaCl solutions showed an increase in current due to hydrogen evolution reaction (HER), and the cathodic current due to HER on steel was larger in the MgCl2 solution than in the NaCl solution. To investigate the difference in HER in both solutions, the steel surface was observed after constant polarization at -1.0 V for 20 min. Mg(OH)2 deposition was observed on the steel surface in the MgCl2 solution, but not in the NaCl solution. This indicates that the increase in pH due to ORR and HER is mitigated by the formation of Mg(OH)2 during cathodic polarization. Therefore, due to the pH buffering action of Mg2+ associated with the formation of Mg(OH)2, it can be considered that a larger HER current flowed in the MgCl2 solution than in the NaCl solution when compared at the same potential.On the other hand, cathodic polarization curves for steel in MgCl2 and NaCl solution containing Zn2+ were investigated. As a result, ORR and HER were observed at potentials down to -1 V in the MgCl2 and NaCl solutions containing Zn2+; the cathodic current due to ORR and HER in the MgCl2 and NaCl solutions containing Zn2+ was reduced compared to the solutions without Zn2+. The inhibition of ORR and HER can be attributed to the precipitation of Zn corrosion products.These results suggest that in solution environments containing Mg2+ and Zn2+, the promotion of HER by the effect of Mg2+ and the inhibition of HER and ORR by Zn corrosion products occur simultaneously.

ELECTROCHEMICAL REDUCTION OF CADMIUM IONS FROM ETHYLENE GLYCOL ELECTROLYTE

The work is devoted to the study of the process of cathodic reduction of Cd ions from anhydrous ethylene glycol electrolyte. The mechanism of the process of cadmium reduction was studied by taking linear and cyclic potentiodynamic polarization curves. The influence of cadmium chloride concentration, potential sweep rate and temperature on the process of electrochemical deposition of cadmium ions was studied. With an increase in the concentration of cadmium in the electrolyte, the rate of its release at the cathode increases. Precipitates of good quality are obtained at current densities of 25 mA/sm2. It has been established that the cadmium deposition potential almost does not change with increasing potential sweep rate. The dependence of cadmium electrodeposition from ethylene glycol electrolyte on temperature was studied, which made it possible to establish the optimal deposition temperature, which was 363–373 K, and to conclude that the deposition process is controlled by electrochemical polarization. The diffusion coefficient of cadmium ions to the cathode surface has been calculated

Anode Process on Platinum in Low Temperature KF-AlF3-Al2O3 Based Melts: An Update

The present paper is devoted to obtaining new fundamental data on the electrochemical behavior of oxygen-evolving anodes in fluoride-oxide melts. In this work, the function of platinum and basics of its anode behavior as an ideal oxygen-releasing anode during electrolysis of the low temperature KF-AlF3-Al2O3 based melt were studied by potentiometric, cyclic voltammetric, and chronopotentiometric methods. The influence of the electrolyte composition, temperature, atmosphere, potential sweep rate, current density on the kinetics of the anode process was investigated. In order to clarify the mechanism of the process under study, electrolysis testing was carried out to inform an analysis of platinum oxidation products. Based on the experimental results, the validity of an earlier proposed scheme of the anode process on platinum when carrying out electrolysis of low temperature KF-AlF3-Al2O3 based melts was confirmed. Results will be used for theoretical modeling and studying the kinetics of the anode process on an over oxygen-evolving anodes in the fluoride-oxide melts.

Effect of calcium doping on the anodic behavior of E-AlMgSi (Aldrey) conducting aluminum alloy in NaCl electrolyte medium

The design of new materials intended for operation under severe conditions faces the task of rendering the materials corrosion resistant. The practical solution of this task is interrelated with the knowledge of corrosion protection of metals and alloys. The use of conducting aluminum alloys for the manufacture of thin wire may encounter specific problems. This is caused by the insufficient strength of these alloys and a small number of kinks before fracture. Aluminum alloys have been developed in recent years which even in a soft state have strength characteristics that allow them to be used as a conductive material. The E-AlMgSi (Aldrey) aluminum alloy is a well-known conducting alloy. This alloy is a heat-strengthened one, possessing good plasticity and high strength. After appropriate heat treatment this alloy acquires high electrical conductivity. Wires made from this alloy are almost exclusively used for air transmission lines. This work presents data on the corrosion behavior of calcium containing E-AlMgSi (Aldrey) aluminum conducting alloy in 0.03, 0.3 and 3.0% NaCl electrolyte medium. The anodic behavior of the alloy has been studied using a potentiostatic technique with a PI-50-1.1 potentiostat at a 2 mV/s potential sweep rate. Calcium doping of the E-AlMgSi (Aldrey) aluminum alloy increases its corrosion resistance by 15–20%. The corrosion, pitting and repassivation potentials of calcium doped alloys shift toward the positive region. An increase in the sodium chloride electrolyte concentration leads to a decrease in these potentials.

Effect of calcium doping on the anodic behavior of E-AlMgSi (Aldrey) conducting aluminum alloy in NaCl electrolyte medium

The design of new materials intended for operation under severe conditions faces the task of rendering the materials corrosion resistant. The practical solution of this task is interrelated with the knowledge of corrosion protection of metals and alloys. The use of conducting aluminum alloys for the manufacture of thin wire may encounter specific problems. This is caused by the insufficient strength of these alloys and a small number of kinks before fracture. Aluminum alloys have been developed in recent years which even in a soft state have strength characteristics that allow them to be used as a conductive material. The E-AlMgSi (Aldrey) aluminum alloy is a well-known conducting alloy. This alloy is a heat-strengthened one, possessing good plasticity and high strength. After appropriate heat treatment this alloy acquires high electrical conductivity. Wires made from this alloy are almost exclusively used for air transmission lines. This work presents data on the corrosion behavior of calcium containing E-AlMgSi (Aldrey) aluminum conducting alloy in 0.03, 0.3 and 3.0% NaCl electrolyte medium. The anodic behavior of the alloy has been studied using a potentiostatic technique with a PI-50-1.1 potentiostat at a 2 mV/s potential sweep rate. Calcium doping of the E-AlMgSi (Aldrey) aluminum alloy increases its corrosion resistance by 15–20%. The corrosion, pitting and repassivation potentials of calcium doped alloys shift toward the positive region. An increase in the sodium chloride electrolyte concentration leads to a decrease in these potentials.

Diagnostics of supercapacitors using cyclic voltammetry: Modeling and experimental applications

In this article, we analyzed a method of cyclic voltammetry (CV) with respect to diagnostics of supercapacitors. The main goal deals with the study of the voltage sweep rate limits allowing to reach equilibrium conditions during recording of CV curves. A mathematical model of cycling based on the De Levie model has been developed. Using this model, the CV curves of a supercapacitor with two symmetric porous electrodes and a separator have been calculated numerically for different sweep rates. These curves are in a good agreement with experimental CV curves. For the first time, an exact analytical solution is obtained for linear voltage sweep for a symmetric supercapacitor during the charge process. The concept of equilibrium CV curves is proposed and the criterium for the equilibrium conditions depending on voltage sweep rate and other parameters of the system is established. When the potential sweep rate exceeds the equilibrium conditions, the CV curves deviate from a rectangular shape and take the form of a “modified ellipses with sharp edges”. A review of publications related with experimental measurements of CV curves has been provided using the developed concept of equilibrium conditions. Application of themathematical model to experimental CV curves makes it possible to reveal the presence of Faraday reactions.

Analysis of the Nucleation and Growth of Pd-Co on Glassy Carbon from Ethaline at 298 K Using the Theoretical Model for Bimetal Phases

In this project, the process of Pd-Co bimetallic electrodeposition on glassy carbon was studied using a choline chloride and ethylene glycol deep eutectic solvent (DES) at a temperature of 25 °C. The methodology applied for the electrochemical study comprised usual electrochemical techniques such as cyclic voltammetry (CV) and Chronoamperometry (CA). The latter showed the alloy reduction peaks, as well as the potential interval and sweep rates where a satisfactory response of the deposits was established. In addition, the type of nucleation of the alloy NPs is presented through theoretical models, as well as the value of the (apparent) diffusion coefficient, numerical density of active sites and nucleation frequency. Finally, the conclusions obtained prove that the DES used was as an optimal medium that favored the electrodeposition of the Pd-Co alloy.

АНОДНОЕ ПОВЕДЕНИЕ АЛЮМИНИЕВОГО СПЛАВА АlМg5.5Li2.1Zr0.15 ЛЕГИРОВАННОГО КАЛЬЦИЕМ В СРЕДЕ ЭЛЕКТРОЛИТА NaCl

Duralumin alloy is widely used in the aircraft industry, in the production of high-speed trains (for example, Shinkansen trains) and in many other branches of mechanical engineering (since it is significantly more durable than pure aluminum). Along with high operational properties, the diverse use of duralumin is due to its high technological efficiency, which creates prerequisites for obtaining products by all known methods of casting and plastic processing. Duralumin belongs to the category of structural alloys, which are characterized by increased strength. They are based on aluminum. Copper, manganese, and magnesium are used as additives in different percentages. The properties of duralumin depend on the heat treatment and the amount of alloying elements added. The article presents the results of a study of the effect of calcium on the anodic behavior of aluminum alloy АlМg5.5Li2.1Zr0.15 of the duralumin type in the medium of the NaCl electrolyte. The study of the corrosion−electrochemical behavior of alloys was carried out by a potentiostatic method in a potentiodynamic mode with a potential sweep rate of 2 mV ⋅ s ^(-1). It is shown that calcium additives reduce the rate of anodic corrosion of the initial alloy АlМg5.5Li2.1Zr0.15 by 8-10%. It was found that an increase in the concentration of chloride ions contributes to an increase in the rate of anodic corrosion regardless of the calcium content in the alloy АlМg5.5Li2.1Zr0.15.

Потенциодинамическое исследование свинцового баббита БЛа (PbSb15Sn10) с лантаном в среде электролита NaCl

The results of a corrosion-electrochemical study of the effect of lanthanum additives as an alloying component on the anodic behavior of lead babbit of the BLa brand (PbSb15Sn10), in a NaCl electrolyte medium with a concentration of 0.03; 0.3 and 3.0 % (by weight) are presented. The anodic behavior of babbits was investigated by the potentiostatic method at a potential sweep rate of 2 mV/s. The lanthanum content in lead babbit BLa (PbSb15Sn10) was 0.01, 0.1, 0.50 and 1.0 % (by weight). It was found that with an increase in the concentration of chloride ion in the NaCl electrolyte, there is a shift in the negative region of the values of the potentials of corrosion, pitting formation and repassivation of babbits. The free corrosion potential of lead babbit shifts from time to time to the positive region. Regardless of the composition of babbits, an increase in the rate of their corrosion was established with an increase in the concentration of NaCl in the electrolyte. The addition of lanthanum to lead babbit increases its corrosion resistance. It is shown that lead babbit corrodes by the pitting mechanism and lanthanum as an alloying component of lead babbit BLa (PbSb15Sn10) contributes to the shift of the potentials of pitting formation and repassivation to the region of positive values. This leads to an increase in the resistance of lead babbit to pitting corrosion, and also contributes to the healing of incipient pitting foci.

Anode behavior of aluminum alloy AB1 with magnesium

In modern technology, the main advantages of aluminum alloys as structural materials are lightness, pliability to stamping, corrosion resistance (in air, aluminum is instantly covered with a strong film of Al2O3, which prevents its further oxidation), high thermal conductivity, and non-toxicity of its compounds. These properties have made aluminum alloys the main raw material in the aviation and aerospace industries and, more recently, as a composite material. Regarding specific strength (the ratio of ultimate strength to density), aluminum alloys are significantly superior to steel. Therefore, in the article, the electrochemical properties of the aluminum alloy AB1 with magnesium in the NaCl electrolyte medium were studied by the potentiodynamic method with a potential sweep rate of 2 mV / s. It is shown that alloying the AB1 alloy with magnesium up to 1.0 wt.% Increases its anodic stability by 30% in the NaCl electrolyte environment. It was found that with an increase in the concentration of chloride - ion, the corrosion rate of alloys increases, and the potentials of free corrosion, pitting formation, and repassivation of alloys decrease. An increase in the content of the alloying component shifts the indicated potentials to the positive region.

Коэффициенты диффузии комплексов неодима (III) в эквимолярном расплаве NaCl — KCl — NdCl3

The paper presents results of electrochemical behavior of neodymium trichloride in the NaCl — KCl melt. It was shown that the process of neodymium electroreduction in the NaCl — KCl — NdCl3 melt proceeds in two stages. It was established by using the diagnostic criteria of voltammetry that the discharge process of Nd (III) to Nd (II) at the potential sweep rate in the range of 0.6 ≤  ≤ 1.0 V · s-1 is not complicated by reaction disproportionation. In this study diffusion coefficients and activation energy of diffusion for Nd (III) complexes in the NaCl — KCl melt were determined.

TK diagrams to determine the impact of pH variation on 3D printed CoCr alloy implant corrosion

Thermo-kinetic (TK) diagrams are developed for an additively manufactured (AM) CoCr alloy in 0.1 M Na2SO4 in the pH range of 4 to 9 at a constant temperature of 37 °C. The effect of 100 ppm chloride in these solutions was also investigated. TK diagrams can be used to estimate the corrosion rate of the AM CoCr alloy as a function of solution potential and pH. For instance, based on the potentiodynamic polarization results obtained at an optimized potential sweep rate (1.0 mV/s), the passive film had reduced stability at potential > 0.2 VSHE, within 5 < pH < 7, and in the presence of 100 ppm Cl−. Similarly, the CoCr alloy has poor corrosion resistance at potentials lower than 0.8 V vs SHE within 5 < pH < 7, which may be due to the conversion of Cr(OH)3 into soluble CrOH2+ species. The TK diagrams can be used to predict the corrosion rate of CoCr alloys during changes in pH, which may be important during wound healing for implants.