Polarization Curve Technique Research Articles

A Real Case: How to Combine Polarization Curve and EIS Techniques to Identify Problematic Cells in a Commercial PEM Stack

Nowadays, the mobility sector is assessing different technologies to substitute the internal combustion engines in order to reduce its CO2 emissions; one of these possible alternatives is the Polymer Electrolyte Membrane (PEM) fuel cell. So, the development of non-destructive diagnostic tools that could identify defective cells and/or any malfunctioning behavior and can be easily embarked on in any vehicle will expand the durability of PEM fuel cells, improve their performance, and enable them to carry out predictive maintenance. In this research, we use an in-house developed methodology that combines the polarization curve and electrochemical impedance spectroscopy (EIS) techniques to characterize different cells of a commercial PEM stack, identifying malfunctioning ones.

Characterization, inhibition efficiency and DFT simulation of 1,2-bis(2-bromobenzylidene)hydrazine towards aluminum 1050 in H2SO4 1M

In this study, 1,2-bis(2-bromobenzylidene)hydrazine (BBBH) has been synthesized and for the first time its corrosion inhibition efficiency was studied for pure aluminum corrosion in 1M sulfuric acid using polarization curve technique. After treatment of experimental data at 298 K, the results revealed that the compound is a good inhibitor and the efficiency increase with its concentration, to attain 83.23 % for 600 ppm. The adsorption process of this Schiff base on aluminum surface obeys Langmuir isotherm. To complete the inhibition study, thermodynamic parameters including activation energy, Gibbs free energy, were discussed. In order to characterize the Aluminum surface, scanning electron microscopy (SEM), DRX and X-ray photoelectron XPS were used to demonstrate the effect of the inhibitor and the formation of a protective layer. The molecular electronic structure of the title compound was established using the density functional theory (DFT) approach to understand molecular geometry, stability, and chemical reactivity. The FTIR, UV, 1H-NMR and Raman spectroscopy were further applied to examine its purity.

Robust solid slippery surface for anti-corrosion: Experimental and simulation

Corrosion has long been an enduring obstacle for researchers. It is a challenge to make progress in corrosion protection technology and understanding corrosion mechanisms for quite some time. In recent years, the slippery surface has been applied for anti-corrosion. This novel surface gives new expectation to corrosion protection technicians. Even though some researchers have constructed lots of slippery surfaces for anti-corrosion, the robustness should be improved and the intrinsic anti-corrosion mechanism also needs to be clarified. Therefore, we fabricated a solid slippery surface (SSS) via electrodeposition combined with hydrothermal method followed by solid lubricant infused into a micro-nano “metasequoia” structure. The anti-abrasion performance was enhanced due to the special structure as well as the solid lubricant. Besides, the SSS showed thermal assisted self-healing property even after experienced abrasion. The corrosion resistance was evaluated by electrochemical experimental with the potentiodynamic polarization curve and alternating-current impedance technique. The Ecorr and Icorr of SSS were 0.029 V and 2.121 × 10−9 A·cm−2, respectively. Furthermore, the diffusion behavior and relative concentration of corrosive particles were analyzed by the molecular dynamics simulation method. The simulation results showed that the as-prepared SSS can provide a very superior anti-corrosion property with a simulated diffusion coefficient of 2.2 × 10−9 m2·s−1 for Cl−. This work provides technical guidance and theoretical support for the application of SSS in corrosion protection and can provide a reference for the anti-corrosion mechanism of SSS.

A New Imidazole Derivative for Corrosion Inhibition of Q235 Carbon Steel in an Acid Environment.

Q235 carbon steel is a commonly used engineering material, but its application in marine environments is limited by its susceptibility to corrosion, especially localized corrosion that can lead to material perforation. Effective inhibitors are crucial to addressing this issue, particularly in acidic environments where localized areas become increasingly acidic. This study reports the synthesis of a new imidazole derivative corrosion inhibitor and evaluates its effectiveness in corrosion inhibition performance using potentiodynamic polarization curve and electrochemical impedance spectroscopy techniques. High-resolution optical microscopy and scanning electron microscopy were employed for surface morphology analysis. Fourier-transform infrared spectroscopy was used to explore the protection mechanisms. The results demonstrate that the self-synthesized imidazole derivative corrosion inhibitor offers an excellent corrosion protection performance for Q235 carbon steel in a 3.5 wt. % NaCl acidic solution. This inhibitor can provide a new strategy for carbon steel corrosion protection.

Preparation and corrosion resistance of Ni-Fe layer double hydroxides superhydrophobic film on carbon steel

The nickel-ferric layered double hydroxides (NiFe-LDHs) film which are commonly used as catalysts was fabricated on Q235 steel in-situ via two-step hydrothermal method. And the superhydrophobic NiFe-LDH-PFDTES film was obtained by 1 H, 1 H, 2 H, 2 H-perfluorodecyltriethoxysilane (PFDTES) modification. To a certain extent, the application of NiFe-LDHs has been broadened. The structure and composition of NiFe-LDHs film and NiFe-LDH-PFDTES film were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and Fourier transform infrared (FT-IR). The wettability of films was analyzed by water contact angle testing. And the corrosion resistance of NiFe-LDHs and NiFe-LDH-PFDTES film in 3.5 wt% NaCl solution were measured by using potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) techniques. The results show that NiFe-LDHs and NiFe-LDH-PFDTES film were successfully prepared on the surface of Q235 steel. By adjusting the preparation conditions, the NiFe-LDH-PFDTES film with optimal corrosion resistance was prepared in the condition containing the hydrothermal solution concentration is 1 unit and hydrothermal time for 6 h. The hydrophobicity changes little with the hydrothermal parameters, and all reach the state of superhydrophobic, the contact angle is greater than 150°, the sliding angle is less than 1°. For the superhydrophobic film, NiFe-LDHs has excellent synergy with PFDTES, covering of an "air film" on the rough structure of LDHs, blocking the solution from contact with the substrate, thereby providing corrosion resistance. NiFe-LDH-PFDTES film exhibits much better corrosion protective performance than NiFe-LDHs film in 3.5 wt% NaCl solution, the impedance modulus is increased about 4–5 orders of magnitude compared with Q235 steel, and the highest protection efficiency can reach 99.99%.

Bioinspired superhydrophobic surface via one-step electrodeposition and its corrosion inhibition for Mg-Li alloy

The extremely low corrosion resistance of Mg-Li alloy is a critical obstacle to overcome for its practical usage. In this work, targeting this hard problem, we prepare bioinspired superhydrophobic surface onto Mg-Li (LA141) alloy (contact angle up to 167.4° with the sliding angle as low as 1°) for corrosion prohibition by a facile one-step electrodeposition. Transient image capture technique reveals the dynamic interaction between water droplet and superhydrophobic surface, demonstrating the strong repellency to water phase. Superhydrophobic surface plays an essential role in limiting the time of wetness, so that the opportunity for corrosion will be substantially decreased. In atmospheric condition, the corrosion inhibition capability of superhydrophobic coating to Mg-Li alloy is revealed by scanning Kelvin probe. In water immersion state, the electrochemical impedance spectroscopy and the potentiodynamic polarization curve technique is used to uncover the corrosion resistance of the superhydrophobic coatings prepared under different voltage and time. The electrochemical impedance obtained at 40 V after electrolysis for 30 min is up to 5.62 × 105 Ω cm2, which is about 104 times larger than that of the bare state Mg-Li alloy. Meanwhile, the corrosion current density is about 4.36 × 10−8 A/cm2, which is ca. 4 orders of magnitude lower than that of bare Mg-Li alloy, suggesting great corrosion resistance property of the prepared coating in this work.

A facile one-step route to fabricate bio-inspired superhydrophobic matrix with high corrosion inhibition to Cu metal

Bio-inspired by nature, superhydrophobic surface provides opportunities in the field of material protection. In this research, a single one-step electrodeposition procedure has fabricated superhydrophobic (SHP) coating based on Ca-myristic acid complex onto Cu substrate. The as-fabricated superhydrophobic surfaces possess extremely low surface adhesive force to water phase and excellent self-cleaning and antifouling ability. Using different electrochemical approaches including scanning Kelvin probe (SKP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve techniques, the coating is revealed to protect Cu substrate from corrosion. After being soaked in 3.5wt% NaCl solution for 120 h, corrosion current density of SHP Cu is still much lower (1/27.5) than that of bare Cu. In addition, through 5.0wt% NaCl salt spray experiment, the corrosion current density of SHP Cu decreases to 5.49×10−5 mA/cm2, which is much lower than that of the bare Cu (1.02×10−6 mA/cm2). Therefore, the SHP coating can be potentially used to protect Cu from corrosion in harsh environment.

Experimental and computational study of zinc coordinated 1-hydroxyethylidene-1,1-diphosphonic acid self-assembled film on steel surface

Zinc coordinated 1-hydroxyethylidene-1,1-diphosphonic acid (Zn-HEDP) film was fabricated on steel surface by coordination self-assembly method. The surface morphology and chemical composition of Zn-HEDP film were investigated by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the structural and valence state of Zn-HEDP film was determined by Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of Zn-HEDP film in 3.5wt% NaCl solution was investigated by using potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) techniques. The experimental results show that Zn-HEDP film is in a smooth surface with disturbed nanoparticles. The protection efficiency of Zn-HEDP film to steel in 3.5 wt% NaCl solution is firstly increased and then decreased with the increasing of zinc concentration, pH value and assembly time. The optimum preparation conditions for Zn-HEDP film are the zinc concentration of 10 mmol/L, pH value of 5.0 and assembly time of 30 min, under which the protection efficiency of film is reached to 95.79 %. The coordination between zinc ions and HEDP can effectively increase the binding energy with Q235 steel. Zinc ions can improve the compactness and thickness of Zn-HEDP films as bridging agents, which prevent Q235 steel from corrosive solution.

To improve the high temperature polymer electrolyte membrane fuel cells performance by altering the properties of catalyst layer

The structure of electrochemical reaction zone and the catalyst layer (CL) thickness affect the performance of high temperature polymer electrolyte membrane fuel cells. In this study, the physical structures and compositions of CL are investigated by electron microscopy and polarization curve techniques. The Pt concentration of Pt/C decides the thickness of CL when the Pt loading is fixed. A higher weight percentage Pt/C contains a lower amount of carbon powder results in a thin CL and limited space for electrochemical reaction. On the other hand, the lower weight percent Pt/C provides larger space and smaller size of platinum catalyst which engenders the electrochemical reaction in CL more easily. The ionomer binds electrocatalysts Pt/C particles together and offers the ion conducting phase. Two different ionomers, Polytetrafluoroethylene (PTFE) and Polyvinylidene difluoride (PVDF), were tested. SEM results showed that PTFE forms a better uniform CL structure than PVDF. With 10 wt% Pt/C, PTFE ionomer possesses a higher gas permeability property which induces a higher reactant flow rate in CL, and consequently results in a 42.9% higher cell potential than the PVDF at 0.4 A/cm2 current density output. A proper combination of 10 wt% Pt/C with PTFE ionomer is able to gain 0.62 A/cm2 output at 0.3067 V for the HT-PEMFC.

Corrosion Behavior of an AISI/SAE Steel Cut by Electropulsing.

The effect of electropulsing treatment (EPT) on the surface general corrosion behavior of an AISI/SAE 1045 steel under different machining regimes is studied. In the study, the following variables are alternated: high-speed steel (HSS) vs. hard metal (HM), and with and without the assistance of high-density electropulses. The corrosion rates are determined using comparative studies such as gravimetric analysis, salt spray chamber test, electrochemical polarization curve techniques (PC), and linear polarization resistance (LPR). Differences in surface microhardness were evaluated by applying optical microscopy and planimetric procedures. Specimens subjected to electropulses and turned with HM reported greater reductions of corrosion rates. Changes in corrosion behavior can be explained in terms of grain shape factor h variation. The present study demonstrates that electropulsing affects the corrosion behavior of AISI/SAE 1045 steel after the turning process.

Biomimetics leading to liquid-infused surface based on vertical dendritic Co matrix: A barrier to inhibit bioadhesion and microbiologically induced corrosion

Inspired by natural plant Nepenthes pitcher, liquid infused surface (LIS) imparts opportunities in material protection fields. In this report, LIS is realized via compositing superhydrophobic cobalt dendrite matrix and silicone oil phase. Firstly, metallic cobalt dendrite is electrodeposited onto Cu substrate. With oxidation, the dendrite is covered by oxide layer on external surface. Further deposition with mussel-inspired polydopamine and dodecanethiol obtains superhydrophobic/superoleophilic dendrite matrix. The infusion of oil phase achieves LIS, which shows high abiotic corrosion inhibition by characterization using scanning Kelvin probe (SKP), electrochemical impedance spectroscopy (EIS) and polarization curve technique. After immersion in seawater for 30 d, |Z|0.01Hz maintains the value of 1.08 × 108 Ω cm2, which is still four orders of magnitude larger than that of bare Cu. Moreover, LIS performs a prominent role to decrease sulfate-reducing bacteria (SRB) attachment on metal surface, which is the precondition leading to microbiologically induced corrosion (MIC), the composite deterioration from both bioactivity of the organisms and corrosion. The attachment density of SRB on LIS after immersion for 3 d and 6 d is approximately three and two orders of magnitude smaller than that of bare Cu. Therefore, by decreasing bioadhesion, the corrosion current density of Cu covered by LIS in SRB medium has drastically decreased, suggesting the promising role for MIC inhibition application.

Electrochemical Evaluation of a Discontinuously Reinforced TiC/Ni-20Cr Composite

ABSTRACTThe work focuses on the analysis of electrochemical corrosion in synthetic salt medium of the TiC/Ni-20Cr composite through the polarization curve technique at four exposure times (0, 6, 12 and 24 h). The composite was prepared by liquid infiltration of the liquid alloy into a porous body of TiC. It was found a continuous and homogeneous distribution of the reinforcing material in the interconnected matrix, having a residual porosity of 6.49 vol.%. According to the electrochemical results, in both samples the highest corrosion rate (CR) was obtained at 12 h exposure due to the rupture of the film of the corrosion products, allowing the interaction of chloride ions with the metal surface. The CR of the composite was slightly higher than that of the alloy at all exposure times, so that the presence of the reinforcing particles and the residual porosity reduce the corrosion resistance of the matrix in the composite. The mechanism of corrosion observed in the alloy and the composite was by pitting, however, the composite also presents crevice corrosion by a differential aeration cell mechanism formed between the metal matrix and the ceramic reinforcement, affected by the residual porosity as confirmed by electron microscopy examination.

Effect of Anode Channel Depth on Cell Performance in Polymer Electrolyte Membrane Water Electrolyser

The Bipolar/Flow field plate is a vital component of Polymer Electrolyte Membrane Water Electrolysers (PEMWE) which enables electronic conduction, provide mechanical support to the cell and facilitates mass transport of liquid water and produced gases to and from the electrocatalyst surface. From a mass transport viewpoint, especially at high current density operation, optimizing the dimensions and configuration of the flow field plate is crucial to reducing mass transport limitation and achieve improved cell performance. This work investigates the effect of channel depth of the anode flow field plate on performance of a PEM Water Electrolyser using polarization curve and Electrochemical Impedance Spectroscopy technique. A single electrolyser cell with flow field plate having a single straight channel was employed having the channel depth varied from 3.0 mm to 8.0 mm and the cell performance was studied at current densities up to 2 A/cm2. The impedance spectroscopy results show that the effect of channel depth on cell performance is negligible at low and medium current densities, but significant at high current densities. The result indicate that the two-phase flow liquid/gas interactions in the flow channel and the flow regime of operation have a direct influence on mass transport losses and overall performance in the PEM Water Electrolyser. Furthermore, the impedance spectroscopy result at high current densities shows that, generally, deeper channels show better performance than shallower channels which suggests that the effective mass transfer area at the surface of the gas diffusion layer increases with increase in channel depth thus yielding improved mass transport. However, the best performance was observed at 4.5 mm depth which suggests that there exist an optimal channel depth where an increase or decrease in depth would lead to loss of performance. This is attributed to the trade-off between reduced liquid flow velocity and reduced surface coverage of gas bubble/slug in the channel with increasing channel depth in the PEMWE flow field. Fig 1: Effect of channel depth on cell performance at (a) low, (b) medium and (c) high current density at water flow rate of 40 mL/min and inlet water temperature of 80°C. Figure 1

Eminently Enhanced Anticorrosion Performance and Mechanisms of X-ZnO (X = C, N, and P) Solid Solutions.

Nonmetal (C, N, P) doped zinc oxide solid solutions (ZnO SSs) prepared through one-step calcination method exhibited novel anticorrosion capability. The anticorrosion property was identified by electrochemical impedance spectroscopy and polarization curve technique. The maximal impedance belonged to C-ZnO SS, which was 12 times higher than pure ZnO materials. Then, a synergistic anticorrosion mechanism was proposed: the photoelectron flow suppression effect and the self-cohering process formed by doping. The tiny particle size as well as the minor zeta-potential of X-ZnO SSs eminently promoted the intermolecular cohesion and the formation of the compact surface automatically. Moreover, the photocatalytic experiments successfully verified the product and the corrosion inhibition effectiveness of the photoelectrons. Additionally, a positive correlation conclusion between the anticorrosion performance and the photocatalytic performance of the X-ZnO SSs was obtained. Consequently, developing the self-cohering anticorrosion materials is of crucial industrial application prospect and value.

Differentiating polarization curve technique for determining the exchange current density of hydrogen electrode reaction

The authors propose a new method to easily and reliably determine the exchange current density (i0) of hydrogen evolution reaction (her). The validity of a novel method named the differential polarization method (DPM) was ascertained by the estimation of i0 on platinum electrode in acid solutions. The hers in 0.005, 0.05 and 0.5moldm−3 H2SO4 solutions were visually categorized as reversible reactions. The obtained i0 had constant values of about 0.5mAcm−2, corresponding to the appearance of a vertical line on the anodic polarization resistance curve. This DPM shows the i0 is corresponds to the limiting diffusion current density of the hydrogen oxidation reaction. We believe that the DPM has the potential to be a beneficial and reliable method for estimating electrochemical parameters.

Membrane Electrode Assembly with Ultra Low Platinum Loading for Cathode Electrode of PEM Fuel Cell by Using Sputter Deposition

AbstractCathode electrodes of proton exchange membrane fuel cells were fabricated by using Pt sputter deposition to increase the gravimetric power density (W mgPt−1) with reduced Pt loading. Ultra low Pt‐based electrodes having Pt loading in between 0.0011 and 0.06 mgPt cm−2 were prepared by a radio frequency (RF) sputter deposition method on the surface of a non‐catalyzed gas diffusion layer (GDL) substrate by changing the sputtering time (20, 90, 180, 1050 s). The effect of cathode Pt loading on the performance of membrane electrode assembly were investigated using polarization curve, impedance, H2 crossover and cyclic voltammetry techniques. The effect of backpressure on PEMFC performance was also investigated. Sputter1050 (0.06 mgPt cm−2) exhibited the best power density at 80 °C cell temperature and without backpressure for H2/O2, 100 %RH (297 mW cm−2 and 5 W mgPt−1 at 0.6 V). On the other hand sputter90 (0.005 mgPt cm−2) showed the peak gravimetric power density (15 W mgPt−1 and 75 mW cm−2 at 0.6 V). The Pt utilization efficiency increased as the Pt loading decreased. Sputter20 and sputter90 electrodes yielded insufficient electrochemical surface area (ECSA), higher charge transfer and ohmic resistance, but sputter180 and sputter1050 yielded sufficient ECSA and lower charge transfer and ohmic resistance.

Electrochemical characteristics of the early corrosion stages of API X52 steel exposed to H2S environments

Electrochemical impedance spectroscopy (EIS) and polarization curve techniques were used to study the early stages of hydrogen sulfide (H2S) corrosion. Results revealed the formation of different iron sulfide compounds during the early stages of corrosion. Meanwhile, Warburg impedance characteristics were determined through EIS. Numerous flake-like mackinawites were observed after 15 h. The diffusion-controlled mechanism gradually disappeared during the process. After immersion for 15 h to 7 d in aqueous H2S, the flake-like mackinawites grew larger and adhered, which increased the thickness of corrosion product films. The EIS and polarization curve tests proved that the increase in thickness of corrosion product films enhances corrosion resistance.

Electrochemical Behaviors of Pb–0.3%Ag-0.06%Ca Rolled Alloy Anode during and after Zinc Electrowinning - Tafel Investigations

In this paper, the oxygen evolution potential and kinetics of Pb–0.3%Ag-0.06%Ca rolled alloy anode during the 15 days electrolysis in acid zinc sulphate electrolyte solution were investigated with galvanostatic polarization curve and Quasi-stationary polarization (Tafel) techniques. The results revealed that the anodic oxygen evolution potential and reaction kinetics varied a lot during the electrolysis for it is a process indicating the formation and stabilization of anodic oxide layer. With the increasing electrolysis time, the potentials (MSE) and overpotentials of oxygen evolution mainly present a declining trend while the electrode surface exchange current density a rising trend.

Study on Electrochemical Behavior of Prestressed Reinforcement in Simulated Concrete Solution

Using electrochemical impedance spectroscop (EIS) and polarization curve technique, the electrochemical behavior of prestressed reinforcement under different stress levels was studied in simulated concrete solution. The results show that: As the stress increasing, the impedance spectroscopy changes significantly, the entire impedance spectroscopy shows an elongated semi-circular deformation, high-frequency capacitance arc radius corrosion decreases with the corrosion progress, in other words, the reaction resistance decreases, the corrosion rate of the sample increases. And when the galvanized steel is in 1064MPa stresss condition, corrosion current density reaches the maximum, is 9 times larger than that of none stress corrosions condition. Under the combined effects of the external stress and corrosive media, dislocation can be emitted, value-added and moves. When it reached a critical state, it would lead to the crack nucleation of Stress corrosion cracking (SCC).

Study of Electrochemical Behavior of the Transmission Tower Galvanized Layer in Simulated Acid Rain Solution

Using electrochemical impedance spectroscopy (EIS), polarization curve and X-ray diffraction technique, electrochemical behavior of the transmission tower material Q460 galvanized layer was studied in simulated acid rain solution. The results show that: galvanized layers take place local corrosion in simulated acid rain solution, the corrosion products will fill the hole, and cover on galvanized layer surface, the generated white corrosion products mainly ZnSO4 ·H2O.The current generate in the process of corrosion, galvanized layer surface take place electrochemical corrosion. Galvanized layer solution at pH 2.4 and 3.8 of the simulated acid rain in the corrosion process is controlled by the charge transfer process, with the decrease of solution pH value, the corrosion rate increases. Zinc are more sensitive to H+ in the solution, in low pH value of solution, due to the strong hydrogen precipitation process, the zinc surface adsorption of hydrogen bubble around, its dissolution rate is higher than the surface of the other part of the zinc, namely in low pH value of acid rain solution, H+ by depolarization process not only directly accelerate the corrosion of zinc, can through the strong hydrogen evolution process at the same time accelerate the dissolution of zinc.