Polarization Curve Measurements Research Articles

Effect ofpHand H2S concentration on sulfide stress corrosion cracking (SSCC) of API 2205 duplex stainless steel

AbstractThe role ofpHvalue and H2S concentration on the sulfide stress corrosion cracking of API 2205 duplex stainless steel was studied by means of slow strain-rate tests, polarization curve measurements and surface analysis. It was found that 2205 duplex stainless steel was highly susceptible to sulfide stress corrosion cracking aspHdecreased and H2S concentration increased. When thepHvalue was 2.8, the susceptibility stayed at a low level in 500 ppm H2S concentration but there existed a critical H2S concentration between 500 ppm and 1 000 ppm, above which the susceptibility rapidly increased. The sulfide stress corrosion cracking resulted from hydrogen-induced cracking and exhibited the characteristics of hydrogen embrittlement. The boundary of a phase and γ phase promoted the initiation of stress corrosion cracking, while γ phase inhibited its propagation.

Highly Active and Durable Membrane Electrode Assemblies for Proton Exchange Membrane Water Electrolyzers Fabricated by Reactive Spray Deposition Technology

The reactive spray deposition technology (RSDT) that has been developed at UConn, is one of the most promising new methodologies for direct fabrication of large scale MEAs for proton exchange membrane water electrolyzers (PEMWEs) with ultra-low platinum group metals (PGM) loadings in their catalyst layers [1,2]. The RSDT is an open to air flame assisted method for fabrication of MEAs that combines the catalysts synthesis and direct deposition on the Nafion® membrane in one step [2,3]. Thus, this method eliminates multiple time consuming and expensive steps in the MEA manufacturing process and reduces the fabrication time from days and weeks to hours. As a dry spray methodology with integrated system for in-situ quality control of the catalysts and catalyst layers (CLs),[1] the RSDT allows precise control of the catalysts composition, loading, porosity, thickness, and ionomer content. Furthermore, it has been demonstrated that by controlling the precursor solutions flow rates, and the flame deposition parameters, catalyst layers with gradient distribution in the nanoparticle size, as well as in the PGM loading in the CLs can be achieved, which ensures fine tuning of the activity and durability performance of the MEAs of interest [4].Herein, we will demonstrate the capabilities of the RSDT methodology to fabricate large scale MEAs for PEMWEs, that have one order of magnitude lower PGM loadings in the CLs and activity and durability performance comparable to the state-of-the-art commercial MEAs. RSDT fabricated MEAs with geometric area of the electrodes of 86 cm2 and 680 cm2, and loadings of 0.2 mgPt/cm2 in the cathode and 0.3 mgIr/cm2 in the anode have been tested at conditions typical for industrial electrolyzers. The performed long term steady-state test for over 5000 hours, as well as the measured polarization curves and EIS spectra clearly show excellent activity and durability performance of these MEAs. In addition, the RSDT fabricated MEAs have integrated recombination layers that effectively reduce the hydrogen crossover to below 10 %LFL. Furthermore, comprehensive post-test analysis of the MEAs after 5000 hours of operation has been performed and the degradation mechanisms governing their performance loss were identified and will be discussed in detail.References https://www.hydrogen.energy.gov/pdfs/review20/ta027_maric_2020_o.pdf Mirshekari, G., Ouimet, R., Zeng, Z, Yu, H., Bliznakov, S., Bonville, L., Niedzwiecki, A., Errico, S., Capuano, C., Mani, P., Ayers, K., Maric, R., 2021.“High-Performance and Cost-Effective Membrane Electrode Assemblies for Advanced Proton Exchange Membrane Electrolyzers: Long-Term Durability Assessment”, International Journal for Hydrogen Energy, 46(2), 2021, pp. 1526-1539.Roller, J., Maric, R., 2015. A Study on Reactive Spray Deposition Technology Processing Parameters in the Context of Pt Nanoparticle Formation, Journal of Thermal Spray Technology, 24(8) December 2015 pp. 1529-1541.Yu, H., Baricci, A., Casalegno, A., Guetaz, L., Bonville, L., Maric, R., 2017. Strategies to mitigate Pt dissolution in low Pt loading proton exchange membrane fuel cell: II. A gradient Pt loading design, Electrochimica Acta, 247(1) 2017, pp. 1169-1179

In-situ Detection of Hydrogen Gas Evolved from Dissolving Mg by Gas-Chromatographic Analysis

The higher rates of hydrogen evolution are observed on Mg and its alloys surface when they are polarized anodically in the electrolyte solution. To clarify this phenomenon, which has been termed “anomalous HE” in recent years1, various real-time hydrogen gas analysis methods have been developed2-10. Our group5,10 have developed an in-situ hydrogen gas detection system during electrochemical measurement of Mg. This system is composed of an electrochemical cell and a gas chromatograph. When the hydrogen gas evolved from dissolving Mg surface during electrochemical measurement, the gases are delivered to the gas chromatograph with the argon carrier gas. Thus, it allows for the qualitative and quantitative analyses of gases evolved from dissolving Mg surface.In the present study, we applied the developed system to in-situ detection of hydrogen gas from magnesium surface under potentiostatic polarization and during anodic polarization curve measurement5,10. The hydrogen evolution rate could be determined successively by calculating from the volume of hydrogen gas estimated by gas-chromatographic analysis at arbitrary time under potentiostatic polarization. In the case of anodic polarization curve measurement of Mg, the cathodic current attributed to the hydrogen evolution reaction could be estimated from the volume of hydrogen gas obtained by gas-chromatographic analysis at arbitrary polarization potential. It indicated that the partial anodic current at each polarization potential could be estimated by the sum of the measured anodic current and absolute value of cathodic current related to the hydrogen evolution reaction by the developed system. On the basis of these results, the measured anodic polarization curve of Mg and partial anodic polarization curve, which could be obtained by the plots of partial anodic current at each polarization potential, are correlated discussed.References M. Esmaily, J. E. Svensson, S. Fajardo, N. Birbilis, G. S. Frankel, S. Virtanen, R. Arrabal, S. Thomas, and L. G. Johansson, Prog. Mater. Sci., 89, 92 (2017).M. Curioni, Electrochim. Acta, 120, 284 (2014).S. Lebouil, A. Duboin, F. Monti, P. Tabeling, P. Volovitch, and K. Ogle, Electrochim. Acta, 124, 176 (2014).S. Fajardo and G. S. Frankel, J. Electrochem. Soc., 162, C693 (2015).Y. Hoshi, R. Takemiya, I. Shitanda, and M. Itagaki, J. Electrochem. Soc., 163, C303 (2016).Y. Hoshi, K. Miyazawa, I. Shitanda, and M. Itagaki, J. Electrochem. Soc., 165, C243 (2018).M. Strebl and S. Virtanen, J. Electrochem. Soc., 166, C3001 (2019).M. Strebl, M. Bruns, and S. Virtanen, J. Electrochem. Soc., 167, 021510 (2020).M. G. Strebl, M. P. Bruns, G. Schulze, and S. Virtanen, J. Electrochem. Soc., 168, 011502 (2021).Y. Hoshi, Y. Hirayama, I. Shitanda, and M. Itagaki, J. Electrochem. Soc., 168, 031510 (2021).

The Effect of Cu Addition on the Corrosion Resistance of High Entropy Alloys

Molybdenum (Mo) has been used as an additive element to improve the corrosion resistance of stainless steels. However, Mo addition sometimes results in the increase of cost. This study focused on copper (Cu) because Cu is also known as an element which improves corrosion resistance of stainless steels. However, Cu addition readily causes the formation of Cu-rich phases in the stainless steels. And, the existence of Cu-rich phases is harmful for corrosion resistance and hot workability. Therefore, Cu content in stainless steels is usually limited below 3 mass%. In this study, the principal of high entropy alloys was applied to fabricate the Fe-alloys containing high concentration of Cu. High entropy alloys (HEAs) are alloys produced by mixing five or more kinds of elements, and it is known that the contribution of configuration entropy to Gibbs free energy becomes large, and a single solid solution phase is generated. The purpose of this study is to make alloys with high Cu contents and clarify the mechanism of improving corrosion resistance by Cu.Equiatomic CoCrCuFeNi and CoCrFeMnNi alloys were prepared by an arc melting method, and pure metals of Co, Cr, Cu, Fe, Ni, and Mn were used as raw materials. For homogenization, a heat treatment was performed at 1200 ℃ for 2 h, followed by water-quenching. The ingots made by arc-melting were cut out into 1 mm in the thickness. After that, the specimen surface was polished up to 1 µm with a diamond paste. The micro-structures were observed using an optical microscope and a scanning electron microscope, and the chemical compositions and elemental distributions of the specimens were analyzed by energy dispersive X-ray spectroscopy. Their crystal structures were identified by X-ray diffraction. Corrosion resistance was evaluated by potentiodynamic polarization and immersion in HCl was carried in. In polarization, Ag / AgCl (3.33 M KCl)was used for the reference electrode, and a platinum sheet was used for the counter electrode. The potential scan was started from 0.05 V below the open circuit potential, and the scan rate was 23 mV min-1. An immersion test in 1 M HCl was performed at 25℃ for 7 days. The mass loss measured, and corrosion rates were calculated.From EDS analysis, in the case of equiatomic CoCrCuFeNi alloy, Cu-rich phases were generated.Matrix phase was solid solution phase containing 9at.%Cu. Co18Cr27Cu9Fe27Ni19, Co18Cr28Cu7Fe28Ni19, Co18Cr29Cu5Fe29Ni20, Co19Cr29Cu3Fe29Ni20, Co19Cr30Cu1Fe30Ni20 and Co19Cr30Fe30Ni21 were prepared based on the matrix phase composition of equiatomic CoCrCuFeNi alloy. From XRD and EDS analysis, when the concentration of Cu was 5at.% or less, it was a single-phase solid solution. The results of polarization curve measurement of these alloys in 1 M HCl, it was found that Cu reduce the current value of active region. From the immersion test results, the addition of Cu reduced the corrosion rate.

High temperature electrochemical reaction parameters affecting elecrochemical corrosion potential of type 316L stainless steel

ABSTRACT High temperature electrochemical reaction parameters for type 316 L stainless steel (316 L SS) have been determined based on data measured in pure water at high temperatures to realize an analytical model that can predict electrochemical corrosion potential (ECP) of 316 L SS without using any adjustment parameters based on ECP data. Behaviors of measured polarization curves for 316 L SS could be explained well with the determined parameters. Calculated ECPs of 316 L SS agreed with measured values in the case that it was acceptable for the model to have an error range of ±0.1 V in a wide oxygen concentration range. However, the error was relatively larger in the range from 10 to 100 ppb oxygen concentration because of the shape of the anodic polarization curve of 316 L SS; in other words, ECP could not be uniquely determined in such an oxygen concentration range. It is expected that the ECP model with the determined electrochemical parameters will have greater validity for, and better interpretability of, the ECPs of SS determined in a boiling water reactor environment.

Corrosion behavior of X80 pipeline steel in oilfield injection water in Eastern China

PurposeThis paper aims to under the laboratory environment, the corrosion behavior of X80 pipeline steel in oilfield injection water in eastern China was studied by immersion test.Design/methodology/approachFirst, the corrosion product film was immersed in oilfield injection water and the effect on the corrosion behavior and the corrosion reaction mechanism were constantly observed during this period. The effect was displayed by potentiodynamic polarization curve and electrochemical impedance spectrums (EIS) measurements. Second, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to observe and test the corrosion product film immersed in the oilfield water for 30 days.FindingsThe results indicate that the tendency of metal corrosion becomes weaker at an early stage, but strengthened later, which means the corrosion rate is accelerating. Besides, it is indicated by impedance spectroscopy that with the decreasing of the capacitance arc radius, the reaction resistance is reducing in this progress. Meanwhile, the character of Warburg impedance could be found in EIS, which means that the erosional components are more likely to penetrate the product film to reach the matrix. The corrosion product is mainly composed of the inner Fe3O4 layer and outer shell layer, which contains a large number of calcium carbonate granular deposits. It is this corrosion under fouling that produces severe localized corrosion, forming many etch pits on the metal substrate.Originality/valueThe experiment chose the X80 steel, the highest-grade pipeline steel used in China, to conduct the static immersion test in the injection water coming from an oilfield in eastern China. Accordingly, the corrosion mechanism and the effect of corrosion product film on the corrosion of pipeline steel were analyzed and discussed.

Study on effect of chloride ions on corrosion behavior of reinforcing steel in simulated polluted concrete pore solutions by scanning micro-reference electrode technique

• Reinforcing steel passivity was detected by scanning reference electrode technique. • Chloride threshold level for the steel corrosion was determined. • Pitting occurred preferentially at MnS inclusion locations on the steel surface. • Chloride ions were adsorbed preferentially at MnS inclusion locations. Chloride ion (Cl - ) attack is a main reason for localized corrosion of reinforcing steel in concrete. Study on the effect of Cl - on corrosion behavior of the steel is of importance for corrosion protection. In this study, reinforcing steel (Q235 carbon steel) passivity in simulated polluted concrete pore solutions at pH 11.50 with different Cl - concentrations was studied by a scanning micro-reference electrode technique, combined with polarization curve and electrochemical impedance spectroscopy measurements and an electron probe method. The results indicated that the steel remained passive in the solution without Cl - . The steel passivity might be destroyed by the Cl - attack, and the pitting corrosion took place. The chloride threshold level for localized corrosion of the steel in the solution was 0.010 to 0.020 M Cl - . Pitting corrosion occurred preferentially at MnS inclusion locations, and the Cl - was adsorbed at these locations resulting in depassivation of the steel surface.

Standardized Procedures Important for Improving Low-Temperature Ceramic Fuel Cell Technology: From Transient to Steady State Assessment.

As the stress–strain curve of standardized metal samples provides the basic details about mechanical properties of structural materials, the polarization curve or current–voltage characteristics of fuel cells are vitally important to explore the scientific mechanism of various solid oxide cells aiming at low operational temperatures (below 600 °C), ranging from protonic conductor ceramic cells (PCFC) to emerging Semiconductor ionic fuel cell (SIFC)/Semiconductor membrane fuel cells (SMFC). Thus far, worldwide efforts to achieve higher nominal peak power density (PPD) at a low operational temperature of over 0.1 s/cm ionic conductivity of electrolyte and super catalyst electrode is the key challenge for SIFCs. Thus, we illustrate an alternative approach to the present PPD concept and current–voltage characteristic. Case studies reveal that the holy grail of 1 W/cm2 from journal publications is expected to be reconsidered and normalized, since partial cells may still remain in a transient state (TS) to some extent, which means that they are unable to fulfill the prerequisite of a steady state (SS) characteristic of polarization curve measurement. Depending on the testing parameters, the reported PPD value can arbitrarily exist between higher transient power density (TPD) and lower stable power density (SPD). Herein, a standardized procedure has been proposed by modifying a quasi-steady state (QSS) characterization based on stabilized cell and time-prolonged measurements of common I–V plots. The present study indicates, when compared with steady state value, that QSS power density itself still provides a better approximation for the real performance of fuel cells, and concurrently recalls a novel paradigm transformation from a transient to steady state perspective in the oxide solid fuel cell community.

A Dynamic Multi-Scale Model for Solid Oxide Cells Validated on Local Current Measurements: Impact of Global Cell Operation on the Electrodes Reaction Mechanisms

A dynamic physically based model has been developed to unravel the complex relationships between the overall Solid Oxide Cells (SOCs) response and the reaction mechanisms taking place in the electrodes. This numerical tool combines modules for different length-scales from the electrode microstructure up to the single repeat unit. First, models have been developed to emulate digital twins of electrode microstructures made of the classical SOCs materials [1]. The microstructural properties of the active layers and the current collectors are then computed on the synthetic volumes and used as inputs in the electrochemical models. The microscale models for the active layers take into account the mass and the charge transport phenomena for the solid and gas phases. For each electrode, the proposed reaction mechanism is split in a sequence of elementary steps with different pathways that can be activated depending on the polarization [2, 3]. The electrode models are finally coupled with a macroscopic description including the cell geometry and the design of the gas channels [4]. This model allows computing the cell polarization curves, the overpotentials and the EIS together with the distribution of the local current density and gas composition in the single repeat unit. This multiscale model has been used to study a typical cell made of the classical SOCs materials: the electrolyte was in Yttria Stabilized Zirconia (YSZ) whereas the hydrogen and oxygen electrodes were respectively composed by a cermet of Nickel and YSZ (Ni-YSZ) and a composite of Lanthanum doped Strontium Cobaltite Ferrite and Ceria doped Gadolinium Oxide (LSCF-CGO). For this cell, the representativeness of the electrodes synthetic microstructures have been checked on reconstructions obtained by tomographic techniques. It has been shown that the synthetic electrodes reproduce accurately the real microstructures. Moreover, the models at the electrode level have been carefully validated on polarizations curves and Electrochemical Impedance Spectra (EIS) measured on symmetrical cells using a three-electrode setup. It is worth noting that the electrodes of the tested symmetrical cells were manufactured using the same materials and composition than the complete cell. Finally, a specific attention has been paid in this work to validate the approach with an original experimental setup allowing the measurement of the local current densities on the full cell without electrode segmentation. This setup is composed of nine symmetrical-spaced pins that perform the measurement of local polarization curves from the inlet to the cell outlet. A campaign of tests has been carried out in fuel cell and electrolysis mode with different temperatures and flow rates. A good agreement has been found between the experimental and simulated data. It has been shown that the model is able to reproduce the evolution of the local polarization curves with a higher current density at the cell inlet. Furthermore, the simulated EIS for the cell have been found to be consistent with the experimental ones. The fully validated model has been used to analyze the cell operation in electrolysis and fuel cell mode. The reaction pathways associated to the elementary steps in the active layers have been discussed depending on the position within the electrodes and the polarizations. This model will then be used to implement the degradation laws such as the Ni agglomeration and compute the loss of cell performances and the remaining useful lifetime [5]. Moreover, the model could be applied to interpret the evolution of the EIS upon operation.[1] H. Moussaoui, J. Laurencin, Y. Gavet, G. Delette, M. Hubert, P. Cloetens, T. Le Bihan, J. Debayle, Stochastic geometrical modeling of solid oxide cells electrodes validated on 3D reconstructions, Computational Materials Science. 143 (2018) 262-276.[2] F. Monaco, E. Effori, M. Hubert, E. Siebert, G. Geneste, B. Morel, E. Djurado, D. Montinaro, J. Laurencin, Electrode Kinetics of Porous Ni-3YSZ Cermet Operated in Fuel Cell and Electrolysis Modes for Solid Oxide Cell Application. Under review. [3] E. Effori, J. Laurencin, E. Da Rosa Silva, M. Hubert, T. David, M. Petitjean, L. Dessemond, E. Siebert, An elementary kinetic model for the LSCF and LSCF-CGO electrodes for solid oxide cells: impact of oxygen partial pressure and degradation on the electrode response. Under review. [4] J. Laurencin, D. Kane, G. Delette, J. Deseure, F. Lefebvre-Joud, Modelling of solid oxide steam electrolyser: Impact of the operating conditions on hydrogen production. Journal of Power Sources. 196 (2011) 2080-2093.[5] M. Hubert, J. Laurencin, P. Cloetens, B. Morel, D. Montinaro, F. Lefebvre-Joud, Impact of Nickel agglomeration on Solid Oxide Cell operated in fuel cell and electrolysis modes. Journal of Power Sources. 397 (2018) 240-251. Figure 1

Performance and thermal optimization of different length-width ratio for air-cooled open-cathode fuel cell

Open-cathode polymer electrolyte fuel cells with compact design have attracted increasing attention in the field of portable energy equipment. This study explores the impacts of different length-width ratios (RL-W) of the cell with the same active area (50 cm2) on cell performance based on various measurements of polarization curves, air velocity profile, and temperature distribution. Results suggest that RL-W has a significant impact on cell performance. Remarkably, a performance improvement of 7% is achieved with the increase of RL-W (4.14–22.40) due to the enhancement of heat and mass transfer ability. The maximum temperature difference at the cathode outlet surface is less than 2 °C when RL-W is 22.40. It is also indicated that the optimum cathode outlet surface temperature is about 48～52 °C. Under the condition of ensuring the structural strength and performance of the cell simultaneously, the appropriate range of RL-W is confirmed as 10–20. The results provide basic data and technical support for the system design and application of open-cathode fuel cells.

Exploring the Structure-Function-Performance Relationship of Carbon Electrodes Toward Rational Design of High-Performance Redox Flow Cells

Redox flow batteries (RFBs) are a promising grid-scale energy storage technology for the integration of intermittent renewable sources, such as wind and solar, into the electrical grid due to their modularity, flexible design, and cost-effectiveness in long-duration storage [1]. Unlike traditional batteries, for RFBs, electrolytes are stored in external tanks and are circulated through the flow cell. In the flow cell, electrical energy is stored via the electrochemical reactions of the redox active species dissolved in liquid electrolytes. While this new archetype provides unique benefits, the flow-assisted nature of RFBs presents many challenging issues, including but not limited to significant transport losses due to the poor electrode and cell design, and the related low power density [2-3]. It can be hypothesized that many of these challenges are primarily related to the concept of electrolyte utilization [4]. In this regard, porous electrode is the key component, which is responsible for multiple critical functions including delivery of liquid electrolytes as well as facilitating ion/charge transfer and providing sites for electrochemical reactions [4]. Despite its importance, the required fundamental knowledge on how to systematically design effective electrodes specifically tailored for RFB applications has not received much attention [5].In this talk, the recent efforts on establishing the structure-function-performance linkages for commercially available carbon electrodes will be presented. The results of the experiments utilizing an electrochemical protocol that combines symmetric flow cell cycling with electrochemical impedance spectroscopy (EIS) and polarization curve (PC) measurements will be discussed. The impedance data is fitted into a mathematical model, and key physicochemical properties of carbon electrodes and the correlated performance losses are quantified. Additionally, we will share our perspective on manufacturing high-performance carbon electrodes using a high-throughput screening platform.

PH Overpotential for Unveiling the pH Gradient Effect of H + /OH − Transport in Electrode Reaction Kinetics

pH Overpotential for Unveiling the pH Gradient Effect of H ⁺ /OH ⁻ Transport in Electrode Reaction Kinetics

Effect of Thermomechanical Treatment on Functional Properties of Biodegradable Fe-30Mn-5Si Shape Memory Alloy

The structure, martensitic γ ↔ e transformation temperatures, Young’s modulus, mechanical properties, and electrochemical behavior of Fe-30Mn-5Si (wt pct) biodegradable shape memory alloy subjected to various thermomechanical treatments (TMT) comprising hot rolling or cold rolling with post-deformation annealing were characterized by optical microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry, tensile testing, open circuit potential, and polarization curves measurements in Hanks’ solution, as compared to reference heat treatment. The optimum combination of mechanical properties (low Young’s modulus, high tensile strength, and appropriate ductility) for biomechanical compatibility was obtained after TMT with hot rolling at 600 and 800 °C due to the formation of favorable dynamically polygonized and recrystallized structures and decrease in the γ↔e transformation starting temperature down to the human body temperature. The TMT did not show a significant effect on the corrosion rate as compared to the appropriate corrosion rate after the reference heat treatment. It is concluded that the TMT with hot rolling at 600 or 800 °C, which provides an optimum combination of the required corrosion rate in the simulation body fluid with high biomechanical compatibility, can be considered a promising treatment of Fe-30Mn-5Si biodegradable alloy for bone implants.

Polarization Curves of Carbon Steel in Concentrated LiBr Solutions Containing LiOH and Li<sub>2</sub>MoO<sub>4</sub> at Different Temperatures after Short Immersion

We have tried to measure polarization curves of SS400 carbon steel in concentrated LiBr solutions over 393 K, and investigated the influence of temperature as well as concentrations of LiOH and Li2MoO4 on its corrosion behavior. Test solutions were 65 mass% (mass% is replaced by % hereafter) LiBr solutions containing 0 to 0.2% LiOH and 0 to 0.03% Li2MoO4. Test temperatures were 393 and 438 K. The test solutions were deaerated. The specimen was immersed in the test solution for a short time of 0.3 ks and was subjected to measurement of polarization curve in the same solution. As a result, the followings were obtained: The anodic current density in 65% LiBr solution without LiOH increased monotonically with a rise in a potential, and the relation was maintained regardless of Li2MoO4 addition and temperature change. In 65% LiBr solutions with LiOH up to 0.2% at 393 and 438 K, the anodic polarization curves showed active dissolution and passivation. When 0.05% LiOH was added to the 65% LiBr solution, the corrosion potential negatively shifted, and the potential was maintained regardless of more addition of LiOH. As a LiOH concentration increased, a pitting potential was raised. The polarization curves at 393 and 438 K showed almost no change regardless of addition of 0.03% Li2MoO4, meaning that Li2MoO4 had almost no effect on corrosion inhibition to the specimen for the short immersion. The corrosion rate at 393 K was approximately 0.3 A·m−2 regardless of the addition of LiOH nor Li2MoO4. Whereas, the corrosion rate at 438 K slightly decreased with increasing LiOH concentration, regardless of the addition of Li2MoO4. Cathodic current density in the solution with 0.2% LiOH and 0.03% Li2MoO4 increased with a rise in a temperature on the basis of Arrhenius relation. It is thought that insufficient effect of LiOH and Li2MoO4 on corrosion inhibition was observed because of a short immersion time of 0.3 ks before measurement of polarization curves.

Communication—In Situ Hydrogen Evolution Detection from Mg Electrode During Anodic Potentiodynamic Polarization Measurement with Gas-Chromatographic Analysis

An in situ hydrogen gas detection system was developed to determine the hydrogen evolution rate (HER) from Mg during anodic potentiodynamic polarization (APP) curve measurement. The system, which is composed of an electrochemical cell and a gas-chromatograph, allows for successive determination of HER during the APP curve measurement because evolved gas was delivered directly to the gas-chromatograph using Ar carrier gas. As the HER could be determined every 104 s after starting APP measurement from corrosion potential, the HER could be plotted against polarization potential. It was confirmed that the HER was correlated with anodic current values in the APP curve.

PEM electrolyzer characterization with carbon-based hardware and material sets

The research and development of proton exchange membrane water electrolysis (PEMWE) is an upcoming and growing area due to a rising interest in hydrogen as an energy carrier. Operating conditions are harsher than in a fuel cell system, particularly because the potentials required for the oxygen evolution reaction are significantly higher. In commercial water electrolysis systems, this is compensated by typically using titanium material sets that are often protected against oxidation through coating processes. Such material choices make small scale research hardware and porous transport layers expensive and difficult to source. In this work, we show that the stability of traditional, carbon-based fuel cell materials such as porous transport layers and graphite flow fields can be sufficient for electrolyzer initial performance characterization procedures such as cell conditioning, a limited number of polarization curve measurements, and electrochemical impedance spectroscopy. We identify and quantify the onset of carbon degradation in porous transport layers with regards to operating length and define a strategy that enables the utilization of standard fuel cell hardware for short-term PEMWE experiments. With the knowledge that existing fuel cell material sets can be applied to conduct electrolyzer research when adhering to such limitations, fuel cell research hardware and experience can be more readily transferred to the younger and rapidly growing electrolysis research field.

Evaluation antioxidant activity and corrosion inhibition of C38 in Hydrochloric acid medium by dried lemon peels of Kenitra Marrakech cities in Morocco and Taiz town in Yemen: A Comparative study

This paper presents a comparative study about the evaluation of antioxidant activity and corrosion inhibition in Kenitra, Marrakesh and Taiz. An interesting topic, indeed polyphenols can improve or help to reduce oxidative stress in the treatment of digestive problems, weight management difficulties, diabetes, hypertension, arteriosclerosis and damage fatty tissue. Therefore, the authors deal with the measurement of polyphenol content and evaluation of the antioxidant activity of lemon peels in Kenitra , Marrakesh and Taiz.The authors performs empirical analyzes on lemon peels. The total polyphenol contents of the ethanolic extract of lemon peels were measured. It was to be 30. 23, 26. 346 and 20.961 mg/CE/g in Kenitra, Marrakech, and Taiz, respectively. Moreover, the DPPH radical scavenging activity of ethanolic extract of dried lemon peels was higher than 200μg/ml concentration. They were 73.47%, 47.36%, and 32.09in Kenitra, Marrakech, and Taiz, respectively. Also, the IC50 values of ethanolic extracts calculated from the percentage inhibitions at the same concentration. Inhibition (IC50) which obtained in Kenitra was 123.089 μg/ml. It was lower compared to the ethanol extract of Marrakech and Taiz that were 197.418, 276.750μg/mL, respectively. Therefore, the extract which is containing a high amount of phenolic is showed high radical scavenging activity. In addition, the maximum inhibition efficiencies for 2 mL L-1 of the inhibitor at 298 k were 98, 12% and 84, 85 % in Kenitra and Taiz, respectively. These values obtained through polarization curve measurements.

Effect of anodic dissolution and passivation on X80 steel in NaHCO3 solution

The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS, AFM and SEM techniques. Under the interference of anodic current (i = 0~200 A/m2), main constituents of corrosion products of X80 steel were FeO(OH) and Fe3O4. A double-layer film formed at i = 100 A/m2, in which FeOOH was in outer and Fe3O4 lied in inner. The formation mechanism of Fe3O4 was confirmed and described by the electrochemical reaction in various regions on anodic potentiodynamic polarization curve.

The Zn2+ Destabilized Surface Film and Accelerated Corrosion of Magnesium

The effect of Zn2+ ions on the corrosion of pure magnesium (Mg) in NaCl solutions was systematically investigated by means of hydrogen evolution, weight loss, surface analysis, polarization curve and solution pH measurements. It was found that the presence of Zn2+ ions in the solution could significantly accelerate the dissolution of Mg. A new mechanism of surface film destabilization was proposed for the detrimental effect of Zn2+ on Mg corrosion, aiming to provide insight into the corrosion behavior of Zn-containing Mg alloys and the galvanic corrosion of Mg alloys coupled by Zn alloys.

Experimental measurements of fuel and water crossover in an active DMFC

This study measured polarization curves as well as the high-frequency resistance of active direct methanol fuel cell (DMFC) operates at around 80 °C with active controls of temperature, methanol concentration, airflow rate, and relative humidity. The relative humidity of the air did not have noticeable impacts on the fuel cell unless the operating temperature was near the evaporation temperature of water (100 °C). The hydrophobic water management layer (WML) between the membrane electrode assembly (MEA) and cathode air channel increases the mass transfer resistance and improves the water retention in MEA. Adding a WML increased the peak power density, decreased the ohmic resistance, and improved the fuel efficiency of the fuel cell, especially when it operated near 100 °C. This study also quantitatively measured methanol and water crossover as well as the fuel efficiency at different operating currents. The fuel efficiency increased significantly with the increase of the current density. Using a hydrophobic fuel management layer (FML) between the anode fuel channel and MEA reduced the fuel and water crossover rates and increased the ohmic resistance due to the decrease of the water content of the Nafion membrane. The FML improved fuel efficiency by reducing the methanol crossover. The combination of the FML and WML enabled the steady operation of DMFC using highly concentrated methanol solutions (up to 75 wt%).