Anodic Dissolution Rate Research Articles

Experimental study on oil removal performance and anodic dissolution characteristics during the treatment of marine oil spills using electrocoagulation

As global demand for oil increases, offshore extraction and transportation activities have become more frequent, leading to a rise in marine oil spill incidents that threaten marine ecosystems. Electrocoagulation technology, known for its efficiency and environmental friendliness, holds potential in treating collected oil-water mixtures during oil spill emergency responses, particularly in controlled environments where the oil has been contained. This study systematically evaluates the oil removal performance and anodic dissolution characteristics of electrocoagulation technology for purifying marine oil spills. The experimental operating parameters ranged from 0.5 A to 1.5 A current, 1.2 L·h−1 to 3.6 L·h−1 flow rate, and 1 cm to 2 cm interelectrode distance. The results indicate that under relatively better operating conditions of 1.0 A current, 1.2 L·h−1 flow rate, and 1 cm interelectrode distance, the oil removal efficiency reaches 90.48 %. The anode dissolution rate is unevenly distributed, with the fastest dissolution occurring in the anode g region, and the dissolution rate increases with the current. Increasing the current inhibits the formation of average pitting depth and expansion of pitting on the anode. This study provides critical data and theoretical support for optimizing the application of electrocoagulation technology for marine oil spill treatment.

Unveiling the effect of bovine serum albumin on the corrosion resistance of high nitrogen stainless steel for cardiac stents

Herein, the effect of bovine serum albumin (BSA) on the corrosion resistance of high nitrogen stainless steel (HNS) is systematically investigated based on experimental characterizations and first-principle calculations. Electrochemical measurements firstly prove that the anodic dissolution rate of HNS has significantly increased due to BSA adsorption and the potential deterioration of the passive film. By subsequent morphology and composition characterizations, it is demonstrated that BSA forms a 1.9 μm porous adsorption layer on HNS surface via the peptide bond mostly in -helix and -turn structure. Furthermore, Mott-Schottky tests confirm that the carrier (cation vacancy) density in the passive film has dramatically risen from 6.29×1021 cm-3 to 1.97×1022 cm-3 after BSA adsorption, which could be ascribed to the detachment of Cr atom from its original lattice due to the preference interaction between BSA molecule and Cr atom. Most importantly, such an increased defects will further promote the dissolution process of both the passive film and HNS matrix according to point defect model (PDM), which will definitely undermine the protective ability of the passive film and eventually result in the declined corrosion resistance of HNS in BSA-contained solution.

Nucleation bubble boundary layer theory for ultra-fast electrochemical polishing of additive manufacturing components

The application of electrochemical-based polishing techniques, including electrochemical polishing (ECP) and plasma electrolytic polishing (PEP), to improve the surface quality of additive manufacturing (AM) components is challenged by the high amplitudes and long spatial wavelengths of roughness, which cause pre-polishing procedures to be indispensable. In this study, a nucleation bubble boundary layer (NBBL) mechanism for enhanced electrochemical-based polishing performance is revealed to solve this problem, namely nucleation bubble electrochemical polishing (NBEP). The NBBL is constructed on the anode surface via electrolytic oxygen evolution and nucleate boiling, and is activated by regulating the temperature and electric potential. The experiments verify a model of NBBL consisting of an inner adherent layer and outer diffusion layer (ODL). Simulations and experiments demonstrate that the polishing mechanism is based on the combined current-limiting effect of individual adherent bubbles and the ODL, which differentiates the anodic dissolution rates at the peaks and valleys of a wide range of spatial wavelengths with their electrical resistance. The bubble dynamics also enhance mass transfer, further improving the polishing efficiency. The experimental results show that NBEP is capable of reducing the surface roughness of AM stainless steel 316 L from Ra of 10.22 μm to 0.71 μm, and eliminating the spatial wavelengths of 200–400 μm in 8 min, which cannot be achieved by either ECP or PEP. The polishing current density also increased from 0.25 (ECP) and 0.48 (PEP) to 2 A/cm2 in NBEP. Finally, a prediction model that accurately describes the ultimate roughness achieved by NBEP as a function of the minimum cavity size is established. The NBEP can be directly followed by PEP or ECP to achieve an optimal surface finish of Ra <70 nm for AM parts. The NBEP method considerably enhances the polishing performance of electrochemical-based systems for AM components, as well as expands the application range of electrochemical-based polishing techniques.

Enhancing primary aqueous magnesium-air battery performance by tailoring anode texture

The mechanisms of the texture generated during the rolling process on the anodes of magnesium-air batteries remain unclear. This work systematically investigates the impact of texture on the dissolution and discharge processes of magnesium anodes using theoretical calculations combined with experiments. Results demonstrate that the ND (Normal Direction) plane of the rolled sheet contained a higher proportion of (0001) oriented grains, exhibiting excellent stability, the slowest anodic dissolution rate, superior corrosion resistance, and enhanced discharge performance. At a current density of 40 mA·cm−2, the discharge capacity and anode efficiency of the ND plane reached impressive values of 1369.86 mAh·g−1 and 61.57%. Additionally, hydrogen evolution, chunk effect, and loss of discharge during the discharge process of AZ31 anodes were quantified for the first time. Furthermore, the effect of texture on the cracking of the discharge product layer was investigated.

Effect of hydrostatic pressure on the anodic dissolution process of X80 steel

Based on the fact that hydrostatic pressure affects chemical potentials of reaction species and the structure evolution of electric double layer (EDL), the authors propose a generalized-BV equation to analyze the anodic dissolution process of X80 steel in deep-sea environment. Combined with the results of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests, the following conclusions can be drawn: hydrostatic pressure can compress the electric double layer non-uniformly. The CHCD (CD: capacitance of diffused layer; CH: capacitance of compact layer) value increases first and then decreases with increasing hydrostatic pressure and reaches its maximum at 15 MPa, which is sure to influence the difference in electrical potential that drives chemical reaction at interface. Ultimately, the anodic dissolution current increases and then decreases with rising hydrostatic pressure at the same anodic polarized potential. Besides, low hydrostatic pressure may contribute to forming a dense corrosion product film and inducing a good inhibiting effect on further dissolution of X80 steel; However, when the hydrostatic pressure exceeds the critical value of 20Mpa, too high anodic dissolution rate along with promoted Cl− adsorption will deteriorate the protection performance of corrosion product film, and exacerbate local corrosion process.

Chrysophyllum Albidum extract as a new and green protective agent for metal

ABSTRACT Gravimetric measurements and potentiodynamic polarization techniques were employed to investigate the protective performance of the metal in 1 M HCl and 0.5 M H2SO4 solutions by the C. albidum leaf extract at different concentrations (400-1600 mg/L) and time periods (1-4 days). The results showed the highest protection ability of over 96-97%, with inhibition increasing with higher extract concentrations. Polarization studies indicated a mixed inhibition mechanism, reducing both anodic dissolution and cathodic hydrogen evolution rates. Gas chromatography–mass spectrometry (GC–MS) analysis identified major organic constituents in the extract. Thermodynamic data fit the Langmuir isotherm model, suggesting chemisorptive adsorption of inhibitor molecules on the mild steel surface. Computational methods, including density functional theory (DFT), molecular dynamics simulations, and quantum chemical calculations, provided insight into inhibitor-metal interactions and adsorption behaviour at the molecular level. Overall, the study establishes C. albidum leaf extract as an effective, sustainable alternative to commonly used toxic chromate and phosphate inhibitors. It performs competitively even at low concentrations and in environments. The promising green inhibition properties, combined with the extract's nontoxicity and abundance from a natural source, suggest its potential as a cost-effective corrosion protection solution, especially for applications in developing economies.

Crevice Corrosion Behavior of 201 Stainless Steel in NaCl Solutions with Different pH Values by In Situ Monitoring.

Crevice corrosion (CC) behavior of 201 stainless steel (SS) in 1 M NaCl + x M HCl/y M NaOH solutions with various pH was investigated using SECM and optical microscopic observations. Results show that the CC was initiated by the decrease in pH value within the crevice. The pH value near the crevice mouth falls rapidly to 1.38 in the first 2 h in the strongly acidic solution, while the pH value was observed to rise firstly and then decrease in the neutral and alkaline solutions. It indicates there is no incubation phase in the CC evolution of 201-SS in a pH = 2.00 solution, while an incubation phase was observed in pH = 7.00 and 11.00 solutions. Additionally, there appeared to be a radial pH variation within the gap over time. The pH value is the lowest at the gap mouth, which is in line with the in situ optical observation result that the severely corroded region is at the mouth of the gap. The decrease in pH value inside results in the negative shift of open circuit potential (OCP) and the initiation of CC of 201-SS. The increased anodic dissolution rate in the acidic solution accelerates the breakdown of passive film inside, reducing the initiation time and stimulating the spread of CC.

Anodic Dissolution Rates Accelerate with Decreasing MoS2 Nanoflake Thickness

Electrochemical gating of 2D transition metal dichalcogenide (TMD) electrodes is an emerging frontier in the field of semiconductor electrochemistry. In this approach, an applied bias modifies the charge carrier concentration of the 2D TMD, causing band edge shifts and drastic changes in charge transfer rates. However, leveraging this effect for (photo)electrocatalysis is practically limited by the stability of the TMD material under gating conditions. Gerischer showed anodic dissolution of bulk TMD electrodes can occur in the dark and hypothesized that the reaction proceeds via an electron tunneling mechanism from surface states to the TMD conduction band [H. Gerischer, D. Ross, and M. Lubke, Z. Physickalische Chem., 139, 1 (1984)]. Here we investigate this possibility in single MoS2 nanoflakes using in situ optical microscopy and explore whether Gerischer’s electron tunneling mechanism can explain anodic dissolution rates of thin 2D semiconductors. Spatially resolved measurements show anodic dissolution initiates at perimeter edge sites and accelerates exponentially with decreasing layer thickness, consistent with Gerischer’s tunneling mechanism. Interestingly, single layer MoS2 is impervious to anodic dissolution at applied potentials >200 mV more positive than those required to drive dissolution in bulk and multilayer-thick nanoflakes.

Initial dissolution of Mg-containing phase and corrosion product formation in cut-edge corrosion of Zn-11%Al-3%Mg-0.2%Si coated steel

Simulated cut-edge specimens of Zn-11%Al-3%Mg-0.2%Si coated steel were fabricated, and their corrosion behaviors were assessed using salt spray test (SST). The Mg-containing phases in the coating near the simulated cut-edge dissolved during early corrosion, leading to the formation of protective corrosion products on the steel surface. The corrosion products suppressed the oxygen reduction reaction on the steel. Additionally, the anodic dissolution rate of the coating layer decreased after the SST. Consequently, the cut-edge corrosion rate of the Zn-Al-Mg coating after the deposition of the corrosion products decreased compared with that of a conventional Zn coating.

Electrochemical and Microstructural Characterization of Cr-Coated NdFeB in Neutral Wet Environment

Naturally, NdFeB–based permanent magnets exhibit high chemical instability, especially, in wet environments. This makes them highly susceptible to corrosion, which leads to severe structural collapse. Applying thin surface coatings can improve the resistance to wet corrosion. In this work, 0.5 µm of chromium (Cr) film was sputtered on a sintered NdFeB–based magnet and the resistance to corrosion and microstructural damage was investigated in 3.5% NaCl solution with respect to an uncoated magnet. This was achieved by complementing potentiodynamic polarization and electrochemical impedance spectroscopy with scanning electron microscopy (SEM). The Cr coating caused a positive displacement of corrosion potential and lowered the rate of anodic dissolution. It also favored higher charge transfer resistance at the magnet–solution interface, and delivers a protection efficiency of ~ 60 %. Furthermore, grain boundary attack and deterioration were also significantly reduced by the Cr coating.

Effect of Acinetobacter lwoffi on corrosion behavior of 7B04 aluminum alloy

In this work, the corrosion of 7B04 Aluminum alloy in cultured A. lwoffi was studied using electrochemical and surface analysis techniques. The study found that the presence of bacteria led to an increase in the pH value of the solution when compared to a sterile system. The electrochemical results indicated accelerated anodic dissolution rate and cathodic oxygen reduction rate of Al alloy, resulting in increased corrosion current density in the A. lwoffi system. Surface analysis, such as scanning electron microscope and stereomicroscope, revealed a large number of corrosion pits, and the severity of the corrosion phenomenon was attributed to the denitrification effect of A. lwoffi, indicating that A. lwoffi promoted the corrosion of Al alloy.

Accelerated development of Ti-6Al-4V microbial corrosion triggered by electroactive sulfate-reducing Desulfovibrio ferrophilus biofilm in enriched artificial seawater containing soluble electron shuttle

In this work, microbial corrosion behavior of Ti-6Al-4V (TC4) alloy caused by electroactive Desulfovibrio ferrophilus biofilm in enriched artificial seawater containing soluble electron shuttle was investigated. The addition of riboflavin-shuttle did not significantly change the planktonic and sessile cell counts but accelerated the microbiologically influenced corrosion of TC4 alloy. The Hilbert-Huang transform revealed the evolution of corrosion pits and the maximum pit depth enhanced with the increase of electron shuttle concentration. Electrochemical measurements proved that riboflavin-shuttle decreased the shuttled electron barrier and increased the anodic dissolution rate. Phase, organization and grain size of alloy were influenced by the MIC.

Effect of Passive Oxide Film Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

Effect of Passive Oxide Film Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

Effect of the Structure of Passive Oxide Films and Surface Temperature on the Rate of Anodic Dissolution of Chromium–Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 1. Anodic Dissolution of Chromium–Nickel Steel in a Nitrate Solution

Effect of the Structure of Passive Oxide Films and Surface Temperature on the Rate of Anodic Dissolution of Chromium–Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 1. Anodic Dissolution of Chromium–Nickel Steel in a Nitrate Solution

Self-Sustained Constant Anodic Dissolution Rate on Iron Electrode Under a Magnetic Field

The evolution of the wavy surface of an iron electrode with anodic polarization time in a sulfuric acid solution under a 0.4 T magnetic field is quantified by 3D tomographic depth profile measurements. The electrode surface after anodic dissolution under a magnetic field is irregular and the 3D profile changes with the anodic polarization time. The anodic dissolution rate is specific to the geometrical location on the electrode, which is, in general, insensitive to the polarization time as well as the surface irregularity.

Enhanced corrosion inhibition of copper in acidic environment by cathodic control of interface formation with 2-mercaptobenzothiazole

Electrochemistry along with advanced surface analyzes (X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry) were implemented to investigate copper corrosion inhibition by 2-mercaptobenzothiazole (2-MBT) in hydrochloric aqueous solution and the effects of electrochemical control on the formation of the inhibiting interface. It is shown that reducing the native surface oxide by cathodic reduction prior to exposure to the inhibitor drastically decreases the rate of anodic dissolution. Additionally, increasing the exposure time of the metal surface to the inhibitor results in even better protection against dissolution. 2-MBT adsorbs as multilayers and bonds to both metallic copper and residual copper oxide islands via its sulphur atoms. Partial dissociation of the molecule, releasing the exocyclic sulphur, which then bonds to metallic Cu, is observed. Further dissociation of the molecule, releasing the endocyclic sulphur, is induced by anodic polarization, forming defects in the organic layer and thus compromising the barrier properties of the organic layer.

Effects of Applied Cathodic Current on Hydrogen Infusion, Embrittlement, and Corrosion-Induced Hydrogen Embrittlement Behaviors of Ultra-High Strength Steel for Automotive Applications

The effects of the electrogalvanizing conditions (a combination of plating current and time) on hydrogen infusion, embrittlement, and corrosion-induced hydrogen embrittlement (HE) behaviors of ultra-high strength steel were examined. A range of experimental and analytical methods, including electrochemical impedance spectroscopy, hydrogen permeation, polarization, and slow strain rate test, were employed. The results showed that the applied cathodic current density during electrogalvanizing had an inverse relationship with the Zn crystalline size. A smaller cathodic current density and longer plating time led to a larger crystalline size, resulting in a higher infusion rate of hydrogen atoms, and HE-sensitivity (i.e., mechanical degradation with larger density of secondary crack in fracture surface). On the other hand, a larger cathodic current density and shorter plating time caused a higher anodic dissolution rate and smaller polarization resistance of the coating when exposed to neutral aqueous environments. Hence, a higher rate of galvanic corrosion between the coating and exposed steel substrate (e.g., locally damaged areas around coating layer) resulted in a higher infusion rate of hydrogen atoms and HE-sensitivity. This study provides insight into the desirable plating conditions for electro-Zn plating on ultra-high strength steels with enhanced resistance to hydrogen infusion and embrittlement, induced by aqueous corrosion.

Effects of aging treatment and pre-deformation on stress corrosion cracking of magnesium alloy

As a medical implant material, the mechanical degradation behavior of magnesium alloy in service environment is of great significance. The Mg–4Zn–0.1Sr alloy is an ideal biomedical alloy, while solute Zn atoms are easy to cause the stress corrosion cracking (SCC) of the alloy. In this paper, the distribution of Zn atoms in Mg–4Zn–0.1Sr alloy is changed by aging treatment, so as to reduce the SCC of the alloy promoted by the Portevin-Le Chatelier effect. In comparison with the as-solutionized alloy, the tensile strength and the elongation of the alloy aged at 160 °C for 400 h in Hanks' solution are increased by 42% and 107%, respectively. In order to improve the aging kinetics, twins and dislocations are introduced by pre-compression. Twins and dislocations promote the diffusion of Zn atoms during aging treatment and make the distribution of precipitates more dispersed. The dislocations can be recovered by aging treatment to avoid promoting anodic dissolution and hydrogen embrittlement. Twin boundaries cannot easily migrate due to the nailing of Zn atoms, the latter of which improves the mechanical properties and leads to grain refinement, and have a good effect on reducing the anodic dissolution rate of the alloy. In comparison with the as-solutionized alloy, the tensile strength and the elongation of the alloy with 3% pre-compression and aging at 160 °C for 200 h are increased by 47% and 77%, respectively. The mechanism of mechanical property improvement of the alloy in Hanks' solution by the thermomechanical treatment is revealed.

Galvanic current analysis of AA6016/SM490 couple using experimental and numerical simulation data in various NaCl solutions

The corrosion behavior of the AA6016/SM490 couple in NaCl solutions was analyzed by experiments and simulations. In experiments, galvanic corrosion occurred between anodic AA6016 and cathodic SM490. In addition, as decreasing in NaCl concentration, the anodic dissolution of SM490 proceeded. From FEM simulations, it was found that as decreasing in NaCl concentration, the anodic current on AA6016 became insufficient to commensurate with the cathodic current on SM490; therefore, the anodic dissolution of SM490 proceeded simultaneously. The anodic dissolution rate of SM490 in 0.5 and 0.05 wt% NaCl was 13 and 18 times larger, respectively, than that in 5 wt% NaCl.

Accelerated anode and cathode reaction due to direct electron uptake and consumption by manganese dioxide and titanium dioxide composite cathode in degradation of iron composite

The movement towards the clinical application of iron (Fe) has been hindered by the slow degradation rate in physiological environments. Herein, manganese dioxide (MnO2) particles were compounded with titanium dioxide (TiO2) particles by mechanical ball milling, and then the mixed powders were incorporated into Fe and fabricated into an implant using selective laser melting. On the one hand, MnO2 had a higher work function (5.21 eV) than Fe (4.48 eV), which inclined electrons to transfer from Fe to MnO2 to accelerate the anode reaction. On the other hand, MnO2 catalysed the oxygen reduction reaction (ORR) through a four-step proton-electron-coupled reaction, which caused more oxygen to flow into the sample to improve the cathode performance. Besides, anatase TiO2 with high conductivity was compounded with MnO2 to construct a composite cathode, which facilitated electron transport from the cathode to the electrolyte, further consuming electrons and promoting cathode reaction. Results showed that Fe-MnO2-TiO2 had a high limiting current density of 5.32 mA·cm−2 and a large half-wave potential of −767.4 mV, indicating an enhanced ORR activity. More significantly, Fe-MnO2-TiO2 had a higher average electron transfer number (2.9) than Fe-MnO2 (2.5), demonstrating a faster electronic consumption reaction and higher cathode performance. In addition, the Fe-MnO2-TiO2 also exhibited fast instantaneous and long-term degradation rates (0.33 ± 0.03 and 0.19 ± 0.02 mm/year), suggesting a high anode dissolution rate. In conclusion, introducing the cathode with high work function and ORR activity provides novel pathways for accelerating the degradation rate of Fe-based implants.