Conventional Anode Research Articles

Vanadium-Doped Bi2S3@Co1−xS Heterojunction Nanofibers as High-Capacity and Long-Cycle-Life Anodes

Lithium-ion batteries (LIBs) are considered one of the most important solutions for energy storage; however, conventional graphite anodes possess limited specific capacity and rate capability. Bismuth sulfide (Bi2S3) and cobalt sulfide (Co1−xS) with higher theoretical capacities have emerged as promising alternatives, but they face challenges such as significant volume expansion during electrochemical cycling and poor electrical conductivity. To tackle these problems, vanadium was doped into Bi2S3 to improve its electronic conductivity; subsequently, a vanadium-doped Bi2S3 (V-Bi2S3)@Co1−xS heterojunction structure was synthesized via a facile hydrothermal method to mitigate volume expansion by the closely bonded heterojunction interface. Moreover, the built-in electric field (BEF) created at the heterointerfaces can significantly enhance charge transport and facilitate reaction kinetics. Additionally, the nanofiber morphology of the V-Bi2S3@Co1−xS heterojunction structure further contributed to improved electrochemical performance. As a result, the V-Bi2S3 electrode exhibited better electrochemical performance than the pure Bi2S3 electrode, and the V-Bi2S3@Co1−xS electrode showed a significantly enhanced performance compared to the V-Bi2S3 electrode. The V-Bi2S3@Co1−xS heterojunction electrode displayed a high capacity of 412.5 mAh g−1 after 2000 cycles at 1.0 A g−1 with high coulombic efficiencies of ~100%, indicating a remarkable long-term cycling stability.

Flower-like graphitic carbon derived from biomass for anode of potassium ion battery

The conventional graphite anode for potassium ion batteries (PIBs) can be structurally disrupted by intercalation of potassium ion with a large radius, resulting in the poor cycling stability and rate capability. Here an architecture of flower-like graphitic carbon (FLGC) derived from biomass is designed. As the anode for PIBs, FLGC achieves the stable performance and high-rate capability because of numerous mesopores, intrinsic defects, and a large interlayer spacing. FLGC presents a stable cycling performance (171mAh g−1 after 1700 cycles at 500 mA g−1 with a capacity retention of 79.2 %) and a high potassium storage capacity (301mAh g−1 at 100 mA g−1), in addition to low charge/discharge plateaus (0.35 V for charge and 0.12 V for discharge). More importantly, the mechanism for potassium storage and influence of intrinsic defects on the electrochemical performance are investigated. This study offers a novel design for graphitic structures, which is important for PIBs.

Heterojunction and vacancy engineering strategies and dual carbon modification of MoSe2-x@CoSe2-C /GR for high-performance sodium-ion batteries and hybrid capacitors

Sodium-ion batteries (SIBs) and hybrid capacitors (SIHCs) have great potential in related electrochemical energy storage fields. However, the inferior cycling performance and sluggish kinetics of Na+ transport in conventional anodes continue to impede their practical applications. Here, we propose a refined design by utilizing well-organized MoSe2 nanorods as precursors and introducing a metal–organic framework and graphene (GR), while resulting in the formation of bimetallic selenide heterostructures/carbon MoSe2-x@CoSe2-C/GR (MCCR) composite through electronegativity. The MoSe2-x/CoSe2 heterostructure can spontaneously form the built-in electric field to accelerate the charge transport, and the formation of anionic Se vacancies induced by electronegativity in situ can provide more active sites for enhancing sodium storage. The presence of external carbon and graphene can act as buffer layers to suppress the volume expansion of MoSe2-x/CoSe2 heterogeneous, and on the other hand, form a conductive network externally to improve electrode conductivity. As anticipated, the MCCR electrode demonstrates superior reversible specific capacity (446 mAh g-1 after 100 cycles) and substantial pseudocapacitance contribution, excellent rate performance in SIB half and full cells. In addition, system electrochemical analysis of multiple ex-situ characterizations elucidates the electrochemical reaction kinetics and transformation mechanism of MCCR electrodes during charging and discharging in depth. When coupled with activated carbon (AC), the MCCR//AC SIHC full hybrid capacitors exhibit impressive cycling stability over 2500 cycles at 1 A g-1 and excellent rate performance, demonstrating their widespread application in energy storage.

Electrolysis-enhanced coagulation process for highly emulsified oily wastewater treatment: Floc diameter, oil removal performance and mechanism

Electrocoagulation (EC) is one of the most effective processes for highly emulsified oily wastewater (HEOW) treatment. However, the demulsification efficiency depends on the amount of aluminum or iron ions released from the conventional sacrificial metal anode, leading to challenges such as rapid anode dissolution and short lifespan. To address these issues, this study presents a novel electrolysis-enhanced coagulation (EEC) process, replacing conventional Al electrodes with dimensionally stable titanium anodes coated with ruthenium-iridium oxide and supplementing the electrochemically released Al³+ with externally added AlCl3.This process was assessed using the Turbiscan LAB Expert to measure the variation in floc diameter under various electrolysis times, AlCl3 concentrations, and current densities. At a current density of 5 mA/cm2 and AlCl3 dosage of 50 mg/L, the mean floc diameter increased from 32.4 ± 1.7 µm to 630.3 ± 76.9 µm as the electrolysis time extended from 0 to 4 min. Under optimal conditions, the oil removal efficiency of 96.7%±0.2% and residual oil concentration in the effluent of 66.3 ± 3.5 mg/L were achieved. The energy consumption of this process was 0.17 kWh/m³, which was a relatively low value compared with conventional EC techniques. Moreover, as electrolysis time increased, a greater proportion of dissolved and suspended Al transformed into species incorporated within the floating oil. These findings demonstrate the potential of the EEC process to replace EC in treating HEOW, providing an effective and durable solution.

Progress in the application of silicon-based materials in lithium-ion batteries anodes

From the battery that powers the remote control to the battery that powers electric cars, lithium-ion batteries (LIBs) are a crucial component of contemporary energy storage. The large theoretical capacity of silicon anodes provides significant benefits inside LIBs. However, the main issue with the conventional silicon bulk anode is its considerable volume expansion, which forms an unstable Solid Electrolyte Interface (SEI) layer during the charge and discharge process and severely reduces battery performance and lifespan. Therefore, to solve these issues, researchers have explored multiple improved silicon anodes, three of which are mentioned in this essay. Firstly, the researchers delve into the usage of nanotechnology. When manipulating silicon particles at the nano-scale, the nano-silicon can mitigate the volume expansion, improving the reaction kinetics. Then, a composite of carbon and silicon is proposed, combining silicon's high capacitance and carbon's high conductivity. After that is the silicon-metal composite, which utilizes metals' mechanical strength and conductivity to stabilize Si anodes further and improve thermal stability. Overall, the significance of this study lies in the exploration of the application of silicon anodes in LIBs, highlighting the potential of these composite materials and advanced technology, which may help guide the future exploration of better silicon anodes.

Stabilizing zinc powder anodes via bifunctional MXene towards flexible zinc-ion batteries

Flexible zinc (Zn) batteries have gained considerable attention as wearable energy storage devices because of their inherent safety and high theoretical capacity. However, conventional Zn anodes suffer from dendrite growth, high rigidity, and poor cycling stability issues, hindering their practical application in flexible zinc-ion batteries. Herein, a dendrite-free and flexible Zn anode is designed using direct ink writing (DIW) printed MXene as a flexible and highly conductive current collector and MXene-wrapped Zn powder (ZnP) as the active material by carefully optimising the rheological properties of MXene-based dispersion. As a result, the synergistic effects of the MXene-based current collector and the MXene protective layer promoted dendrite-free Zn deposition and prevented side reactions, achieving an outstanding cycling performance that exceeded 130 h at a high depth of discharge of 30%. When paired with a Vanadium pentoxide (V2O5)-based cathode, the flexible full cell demonstrated stable electrochemical performance under mechanical deformation and can power electronic devices, presenting a promising pathway for the development of flexible zinc-ion batteries.

Enhancing sustainability and power generation from sewage‐driven air‐cathode microbial fuel cells through innovative anti‐biofouling spacer and biomass‐derived anode

AbstractBackgroundRecently, the concept of the membrane‐less microbial fuel cell (MFC) has gained traction to avoid the high internal resistance that is created upon utilizing conventional membranes. Nevertheless, an overlooked problem arises from the ingress of oxygen from the cathode side into the anolyte solution, fostering the formation of biofilms by aerobic microorganisms on the cathode surface. This biofilm layer poses a formidable impediment, leading to cell disconnection. Moreover, low surface area of conventional anodes is another important issue behind the low power density generation. In this research, a novel approach to circumvent biofilm formation and achieve stable and high‐power‐density output from MFCs by harnessing a commercial antibacterial spacer is introduced.ResultsAir‐cathode, sewage‐driven MFCs showed continuous power generation without the need for external microorganisms. Conversely, the absence of the innovative membrane resulted in a catastrophic power breakdown after 125 h of operation due to the formation of a dense biofilm layer on the cathode. Through the utilization of the proposed membrane strategy, stable power density output of 100 ± 8, 135 ± 11 and 142 ± 10 mW m−2 with carbon cloth, carbon paper and carbon felt anodes, respectively, was achieved. Moreover, a novel anode is introduced from graphitization of grape tree branches. The proposed anode could increase the generated power to 516 ± 17 mW m−2 from the sewage‐driven air‐cathode MFC, more than three times compared to the best conventional anode, carbon felt.ConclusionThis study provides significant solutions for sustainability, low‐performance and high‐cost problems of microbial fuel cells. © 2024 Society of Chemical Industry (SCI).

Improving the Long-Term Protection of Buried Steel Tanks: Considering the Impact of Temperature and Extended Sacrificial Anodes

Corrosion prevention techniques such as cathodic protection (CP) are commonly applied to extend the useful lifetime of buried steel tanks in corrosive environments. Sacrificial anodes effectively supplement CP systems through controlled galvanic corrosion. For buried steel tanks, magnesium-based anodes are regularly used due to suitable current output over extended deployment periods. However, field conditions such as temperature fluctuations and proximity effects between adjacent tanks can influence CP performance. This study numerically simulates the CP of a 3.8 m diameter, 12 m long steel tank which the upper section of the tank is located at a depth of 1 m, protected by uniformly distributed magnesium anodes. To understand the importance of the current output of extended anodes, conventional anodes (i.e., 7.7 kg, 38.7 mA) and extended anodes (i.e., 9 kg, 62.7 mA) were studied. Proximity effects on anodes placed between adjacent buried tanks were also examined. In addition, the influence of temperature and concentration parameters was investigated along with a time-dependent analysis of the protected structure. Under the hottest and coldest conditions, the bottom temperature of the computational domain (in height of 6.8 m) reached 8.7°C and 11.3°C, respectively, with noticeable concentration gradients. The temperature rise necessitated increased protective current, leading to the need for additional sacrificial anodes to meet the demand. The simulation results indicated that the anodes positioned between the two tanks experienced the highest corrosion rate. After 21.5 y, approximately 85% of the mass of these anodes will be lost, with full depletion occurring shortly thereafter. This modeling approach offers valuable insights for selecting the optimal type and placement of anodes, ensuring the long-term integrity of underground infrastructure under varying thermal conditions.

Efficient Electron Injection into Graphullerene Enables Reversible NaC2 Sodium Storage.

Sodium-ion batteries are emerging as promising alternatives to conventional lithium-based technology, offering solutions to challenges in large-scale grid storage. However, the capacity of conventional graphite-based anodes for storing Na-ions is inherently limited by suboptimal thermodynamic interactions and irreversible structural changes that occur in the anode during charge-discharge cycles. Herein, we present a computational design that explores the potential of graphullerene, a two-dimensional framework with interconnected fullerene moieties, for the reversible storage of Na-ions. A unique aspect of this design is the electron injection capacity into the graphullerene anode, reaching 15 electrons per fullerene moiety, which is the highest limit to date. This advancement enables large-scale Na-ion storage up to the stoichiometry of NaC2, exhibiting specific capacity of 551 mAhg-1 and averaged open circuit voltage of 0.18 V vs Na/Na+. In addition, the multilayered arrangement of stored Na-ions enhances the Na-ion diffusivity on the graphullerene surface, leading to rapid insertion and extraction kinetics. Thus, raising the electron injection limit offers a promising strategy to transform carbon-based anodes into suitable candidates for reversible Na-ion storage, without relying on artificial defect introduction or doping.

Engineering electron cloud density of phenazine for high-voltage and long-life alkaline batteries

Alkaline aqueous batteries, with intrinsic high safety and potential for high voltage, have always been a hot research topic. Despite several generations of development of anode materials, they still face the challenge of poor cycling stability. Imines have a significant advantage in stability compared to other n-type materials, but their potential is not low enough compared to metal anodes. Herein, a symmetrically structured, extended π-conjugated imine compound, namely cyano-substituted dotriaconta tetrazaoctacyclo (4CNDTZ), was synthesized for the first time and evaluated as the anode materials for alkaline aqueous batteries. 4CNDTZ exhibits a remarkable capacity of 250 mAh g-1 at 0.2 A g-1, coupled with a remarkably low plateau potential of -0.81 V (vs. SHE), significantly below that of conventional alkaline battery anodes. Advanced characterization techniques alongside theoretical calculations confirm that the active sites crucial for its performance are the CN and CN groups, driving an oxidation–reduction process involving the transfer of 4 K⁺ and 4 electrons. When coupled with Ni(OH)2 cathode, the full cells exhibit a discharge voltage plateau of 1.17 V, allowing the full cells to achieve an energy density of up to 170 Wh kg-1 and sustain stable operation through 10,000 cycles.

Development, characterization and validation of a novel physics-informed equivalent circuit model for silicon–graphite battery cells

The widespread deployment of electric vehicles (EVs), as well as the growing requirements both from manufacturers and consumers, necessitate an increase in energy density with regard to current lithium-ion batteries (LIBs). In this regard, one of the most promising alternatives is the addition of silicon to conventional graphite anodes, thus giving rise to energy-dense LIBs. However, this entails a significant increment in modeling, parameterization and computational complexities due to the interactions between both negative electrode materials. In this article, we present a novel physics-informed equivalent circuit model for cells with blended electrodes, which is able to provide accurate results with respect to a state-of-the-art electrochemical model, not only for the output voltage (≤25 mV RMS), but also internal states, namely active material particle surface concentrations (≤1.2 %) and current distribution (≤2.6 %) at a much lower computational cost. Furthermore, this formulation also allows for a notable simplification of model parameterization. Hence, we describe thorough static and dynamic parameterization processes from half-cell experimental data and impedance measurements. Finally, we validate the proposed model in constant-current as well as dynamic operation, highlighting the influence that the choice of hysteresis model has on the latter. We understand that the presented model is an interesting alternative for the modeling of cells with blended electrodes, and is also suitable for its implementation in Battery Management Systems (BMSs) in EVs.

Breaking the inactivity of MXenes to drive Ampere-level selective oxygen evolution reaction in seawater

The limited activity and stability of conventional anodes in seawater have posed a significant obstacle to sustainable green hydrogen production directly from seawater via electrolysis. To address these challenges, we engineered Ti3C2Tx-MXene by incorporating iron and boron into its matrix (tagged FBT) for selective oxygen evolution reaction (OER). Positioning B underneath the top layer induces charge disparity on the Fe-sites, which influences the subsequent growth of the ZIF-67 metal-organic framework (MOF) on the MXene surface through Fe-O-Co ionic bonds. DFT calculations reveal a favorable binding energy of −2.30 eV at the heterointerface for ZIF-67 adsorption to the surface of FBT via O-Co bond, a shortened bond length of 1.94 Å, confirming the formation of ionic bonds. These ionic bonds tune the active sites for an enhanced and selective OER over chlorine evolution reaction (CER), preventing active Fe species' leaching and ensuring stability at >1.56 A cm−2 in 6 M alkaline seawater over 370 hours. Further, FBT and ZIF-67/FBT require low overpotentials of 521.2 and 508 mV, respectively, to deliver 1 A cm−2 in 6 M alkaline seawater. Our findings demonstrate a robust strategy to significantly expand the potential of MXenes from simple conductive substrates to efficient OER catalysts for seawater splitting and beyond.

Alleviated volume changes of germanium anode via facile chemical confinement strategy

Germanium (Ge) anode shows great promise in overcoming unsatisfied capacity and dendrite formation concerns facing conventional graphite anodes in next generation lithium ion batteries. However, volume changes during repeated alloying and de-alloying cycles seriously impair structural stability and cycle lifespan. In this work, a facile chemical confinement strategy has been firstly proposed to alleviate volume changes of Ge anode. Benefited from strong binding interaction between Ge and ZnS, discrete Ge nanoparticle can be successfully encapsulated within thin protective ZnS shell and N-doped carbon layer (Ge-ZnS@N-C) after two-step carbonization and sulfurization of polydopamine-coating Zn2GeO4 nanorod precursors. In contrast, bulk Ge aggregates and hollow N-doped carbon nanotubes can be formed without chemical confinement of ZnS. The as-prepared Ge-ZnS@N-C sample displays multifold structural merits, including nanosized Ge particles with highly electrochemical activity, sufficient pores and functional groups that facilitate ion diffusion. Besides, protective ZnS shell and N-doped carbon layer can suppress volume changes of Ge nanoparticles and guarantee high electrode reversibility, demonstrated by a series of in-situ and ex-situ experiments. The as-synthesized Ge-ZnS@N-C anodes exhibit stable long-cycle performance (1389.7 mAh/g after 450 cycles at a current density of 0.5 A/g) and excellent rate performance (548.5 and 397.8 mAh/g at 5.0 and 8.0 A/g, respectively).

The Resurgence of Hydrogen Depolarized Anodes: A Catalyst for Change in Industrial Electrochemistry

This presentation delves into the remarkable history of Hydrogen Depolarized Anodes (HDAs) and their relevance to modern industrial electrochemistry. HDAs were originally developed in the early 1970s, but their use has been confined to fuel cell technology and power generation. In the wake of a growing green hydrogen economy and the escalating price of precious metal catalysts, this technology is now emerging as a useful tool to boost the energy efficiency and lower both capital and operational costs of electrified chemical manufacturing processes. Our discussion recounts the evolution of HDA technology, from its conceptual beginnings to its current role as an innovative solution in electrochemical processes.The recent renaissance of HDAs is driven largely by economic and environmental factors. As chemical industries strive to electrify their processes, they also grapple with the rising cost of conventional anode materials. The increasing affordability and availability of hydrogen presents HDAs as a viable and efficient alternative. This shift is not just about cost-saving; it's about embracing a technology that aligns with the principles of sustainability and circular economy.We will explore various applications where HDAs are making a significant impact, such as in the manufacturing of acids and bases, the production of metals such as iron, copper, and zinc, and more experimental processes such as cement production. These examples not only demonstrate the versatility of HDAs, but also underscore their potential in achieving higher energy efficiency than conventional technologies and reducing environmental footprint of a range of industrial operations.Furthermore, our talk will illuminate how HDAs are a stepping stone towards a broader adoption of hydrogen as a cornerstone of industrial electrochemistry. The implementation of HDA technology is more than an innovation; it's a transformative step forward, signaling a new era in chemical manufacturing where sustainability and efficiency go hand in hand.

LaMnO3-Type Perovskite Nanofibers as Effective Catalysts for On-Cell CH4 Reforming via Solid Oxide Fuel Cells.

CH4 has become the most attractive fuel for solid oxide fuel cells due to its wide availability, narrow explosion limit range, low price, and easy storage. Thus, we present the concept of on-cell reforming via SOFC power generation, in which CH4 and CO2 can be converted into H2 and the formed H2 is electrochemically oxidized on a Ni-BZCYYb anode. We modified the porosity and specific surface area of a perovskite reforming catalyst via an optimized electrostatic spinning method, and the prepared LCMN nanofibers, which displayed an ideal LaMnO3-type perovskite structure with a high specific surface area, were imposed on a conventional Ni-BZCYYb anode for on-cell CH4 reforming. Compared to LCMN nanoparticles used as on-cell reforming catalysts, the NF-SOFC showed lower ohmic and polarization resistances, indicating that the porous nanofibers could reduce the resistances of fuel gas transport and charge transport in the anode. Accordingly, the NF-SOFC displayed a maximum power density (MPD) of 781 mW cm-2 and a stable discharge voltage of around 0.62 V for 72 h without coking in the Ni-BZCYYb anode. The present LCMN NF materials and on-cell reforming system demonstrated stability and potential for highly efficient power generation with hydrocarbon fuels.

Fabrication of a Porous Copper/Graphite/Zirconium Oxide Hybrid Anode via Screen Printing for Lithium‐Ion Batteries

AbstractRedesigning anode structures in Li‐ion batteries (LIBs) has been a focus of research aimed at surpassing the energy density of conventional LIBs. Although anode‐free LIBs present a promising architecture, their low Coulombic efficiency is a major drawback. This paper introduces a novel hybrid anode that integrates the current collector (CC) and active materials into a single, cohesive porous structure, which supports both de/intercalation and de/plating reactions. The hybrid anode consists of a porous Cu matrix with embedded ZrO2 powders and graphite; the quantity of graphite is only a third of that present in a traditional graphite anode. The porous structure and additives enhance the electrochemical performance of the hybrid anode by minimizing the Li–electrolyte interactions, forming a stable solid–electrolyte interface and Li4Zr3O8 passivation layer, and reducing the nucleation overpotential. Especially, the unique surface morphology, characterized by a negative curvature between sintered Cu particles, lowers the diffusion potential, which further reduces the nucleation overpotential. Additionally, the periodic mesh‐imprinted top surface, created via screen printing, promotes uniform Li plating. The results demonstrate that the cycling performance and energy density offered by the fabricated hybrid anode are superior to those of conventional graphite anodes.

An experimental study on the hydrogen utilization in air-cooled proton exchange membrane fuel cell stack with a novel anode outlet design

In the realm of portable power system, air-cooled fuel cells stand out for their lightweight design and emission-free operation. Anode purging has emerged as an effective method to alleviate performance degradation in the dead-end anode stack. However, purging frequency can affect hydrogen utilization and output performance. This research aims to reduce the purging frequency and enhance hydrogen utilization of air-cooled fuel cell stacks by introducing a novel anodic outlet endplate. The novel outlet helps to remove liquid water and nitrogen from the stack, improve the output performance, and save the hydrogen usage in the air-cooled fuel cell stack. The peak power outputs of stacks equipped with the novel and conventional anodic outlets are recorded at 2313.95 W and 2213.35 W, respectively. Significantly, the novel anodic outlet configuration demonstrates a 4.54 % increase in peak power. Moreover, this configuration extends the purging interval, leading to a reduction in purging frequency. Under current load of 62 A, the novel anode outlet stack prolongs the purging interval of 134.73 s compare to its counterpart with a conventional anodic outlet than that of the conventional anode outlet. The findings presented in this study are poised to offer valuable insights into optimizing their efficiency and promoting sustainable solutions.

Anodic oxidation of wireless niobium electrode in bipolar electrochemistry

The anodic oxidation of a wireless niobium substrate serving as a bipolar electrode (BPE) in a direct or alternating current electric field was investigated in detail via spectrophotometry, electrochemical measurement, glow discharge–optical emission spectroscopy, and direct microscopic observation. Niobium oxide was a suitable material for the experiment because it is amorphous and can be evaluated through conventional electrochemical methods. It also has a clear interference color, enabling easy optical evaluation. The effect of the BPE configuration (e.g., vertical and horizontal alignments) in the cell on the anodic oxidation area was also investigated visually using the interference color. Transmission electron microscopy observation was also performed for an accurate measurement of the thickness of the anodic film formed on the niobium BPE. Although the basic film formation behavior and film composition were consistent with those in conventional anodization, even in wireless operation, the effective voltage directly contributing to film formation was found to be lower than the applied voltage (30%–70% of the applied voltage), depending on the electrolysis conditions.

Effects of electrode configuration on the current density distribution of the electrolytic reducer

Pyroprocessing for the recycling of light water reactor spent fuel into metal nuclear fuel involves the electrolytic reduction process to convert oxides into metals. Optimization of the electrolytic cell is essential in the current engineering-scale development stage of electrolytic reduction research. This study investigates the effects of the conventional impermeable anode shroud, typically used in the development of laboratory-scale electrolytic reducers, and the effects of parallel multiple electrode configurations, aimed at the scale-up of the electrolytic reducer, on the current density distribution of the electrolytic reducer. The current density distribution was analyzed using COMSOL modeling. The exclusion of the impermeable anode shroud resulted in increased total currents under constant cell voltage conditions and contributed to the narrowing of the current density distribution on the electrodes. In addition, parallel multiple electrode configurations proved effective in increasing total currents and narrowing the current density distribution on the electrodes. These results emphasize the need to use a permeable anode shroud and a parallel multiple electrode configuration to scale-up the electrolytic reducer.

Anodizing of AA2024 Aluminum–Copper Alloy in Citric-Sulfuric Acid Solution: Effect of Current Density on Corrosion Resistance

Al–Cu alloys are widely used as a structural material in the manufacture of commercial aircraft due to their high mechanical properties such as hardness, strength, low density, and tolerance to fatigue damage and corrosion. One of the main problems of these Al–Cu alloy systems is their low corrosion resistance. The purpose of this study is to analyze the influence of anodizing parameters on aluminum–copper alloy (AA 2024) using a bath of citric-sulfuric acid with different anodizing current densities on the thickness, microhardness, and corrosion resistance of the anodized layer. Hard anodizing is performed on AA 2024 Al–Cu alloy in mixtures of solutions composed of citric and sulfuric acid at different concentrations for 60 min and using current densities (i) of 0.03, 0.045, and 0.06 A/cm2. Scanning electron microscopy (SEM) was used to analyze the surface morphology and thickness of the anodized layer. The mechanical properties of the hard anodized material are evaluated using the Vickers hardness test. The electrochemical techniques use cyclic potentiodynamic polarization curves (CPPC) according to ASTM-G6 and electrochemical impedance spectroscopy (EIS) according to ASTM-G61 and ASTM-G106, respectively, in the electrolyte of NaCl at 3.5 wt. % as a simulation of the marine atmosphere. The results indicate that corrosion resistance anodizing in citric-sulfuric acid solutions with a current density of 0.06 A/cm2 is the best with a corrosion current density (jcorr) of 1.29 × 10−8 A/cm2. It is possible to produce hard anodizing with citric and sulfuric acid solutions that exhibit mechanical properties and corrosion resistance similar or superior to conventional sulfuric acid anodizing.