EIS Tests Research Articles

Newly Synthesized Morpholinyl Mannich Bases as Corrosion Inhibitors for N80 Steel in Acid Environment.

New Mannich bases, 3-morpholino-1-phenylpropan-1-one (MPO) and 3-morpholino-1-phenyl-3-(pyridin-4-yl) propan-1-one (MPPO), were synthesized, characterized, and studied as corrosion inhibitors for N80 steel in 1 M hydrochloric acid (HCl) solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and FT-IR spectroscopy. The inhibition efficiency increases with increasing inhibitor concentrations, and the corrosion inhibition efficiency of the MPO and MPPO could reach 90.3% and 91.4%, respectively, at a concentration of 300 ppm at 305 K. The effect of the temperature on the corrosion inhibition behavior of inhibitors was discussed. Electrochemical tests showed that the synthesized inhibitors are mixed. The EIS test results showed that the presence of MPO and MPPO reduced the double-layer capacitance in the corrosion process, thereby reducing the charge transfer resistance. The SEM and EDX results showed that the MPO and MPPO formed a uniform adsorption film on the surface of the N80 steel. The adsorption mechanism of the inhibitors was simulated with different adsorption models and the results showed that the inhibitors were the chemisorbed type. The results of the FT-IR spectroscopy proved that the inhibitor interacted with metal atoms on the steel surface.

Construction of hydrophobic lauric acid film on aluminum alloy and its corrosion resistance mechanism

6061 aluminum alloy is one of the light metal materials, which has the advantages of good elasticity and lightweight. However, aluminum alloy is susceptible to corrosion in industrial applications. Therefore, in this paper, we successfully prepared an organic lauric acid film on the surface of aluminum alloy by electrodeposition. The film was characterized by SEM, EDS, WCA, XPS, EIS, FT‐IR, and neutral salt spray test. According to the results of the EIS test, impedance value has increased by two orders of magnitude compared to the substrate, and corrosion current density reached 8.51 × 10−7 A/cm2. The salt spray test was conducted for 192 h before the corrosion point appeared, indicating that the film have better anticorrosion ion permeability. Calculated chemical results show that COOH of lauric acid is the dominant reaction group and the carboxyl group is near the aluminum alloy surface for the reaction equilibrium state, which provide a theoretical basis for the study of the film.

Fabrication of nanostructured iron-cobalt layered double hydroxide: An innovative approach for the facile synthesis

Studying semiconductive materials-based supercapacitors is significant for developing next-generation energy storage devices. However, the fabrication of a novel semiconductive material-based electrode with self-supporting design, flexible support, and nanoarchitecture is a challenge for the material researcher of 21st century. We present a facile method to fabricate three-dimensional (3D), porous, conductive electrodes based on semiconductive materials with high electrochemical performance. We fabricate the FeCo-LDH sample via hydrothermal route and decorate it on the flexible carbon cloth (CC) to get a flexible and self-supporting electrode. Textural, morphological, elemental, thermal, and functional group studies of the hydrothermally generated powder were performed using XRD, SEM, EDX, TGA, and FTIR methods. Well-known EIS, GCD, and CV tests were used to evaluate the electrochemical possessions of the FeCo-LDH/CC electrode. The performed electrochemical experiments indicated that our manufactured FeCo-LDH/CC electrode has an excellent specific capacity of 1041F/g at 0.5 A/g. Our self-supporting and flexible electrode has excellent cycle stability (it loses only 7.3 percent of its capacity after 5000 GCD cycles). It retains 79.2 percent of its capacitance when the current density increases from 0.5 A/g to 9 A/g. The superior electrochemical activity observed is attributed to the electrode's novel structure and logical design. According to the electrochemical experiment findings, our manufactured FeCo-LDH/CC electrode has great promise for practical applications in next-generation electrochemical capacitors.

Facile fabrication of BiOBrxCl1-x hierarchical microspheres photocatalysts for efficient degradation of diverse pollutants under visible light

The development of excellent photocatalysts is of great significance for the efficient photocatalytic degradation of persistent organic pollutants, but the low carrier separation efficiency and poor light absorption capacity usually restrict the performance of photocatalysts. Herein, we fabricated BiOCl, BiOBr and BiOBrxCl1-x nanosheets (NSs) photocatalysts by a simple one-step hydrothermal approach. BiOBr0.7Cl0.3 nanoplates (NPs) and BiOBr0.7Cl0.3 microspheres (MSs) composites were further synthesized by adjusting the precursor solvent via ethylene glycol-assisted hydrothermal method. Their structural properties were examined by comprehensive characterization techniques. XRD and UV-vis DRS results confirmed that the formation of BiOBrxCl1-x solid solution. PL and EIS tests were used to evaluate the carriers’ separation efficiency of the photocatalysts. The photocatalytic performance was evaluated through the degradation of tetracycline hydrochloride (TC-HCl) under visible light irradiation, and BiOBr0.7Cl0.3 MSs exhibited superior photocatalytic activity, which could degrade 90.40% of TC-HCl under visible light illumination within 40 min. The quenching experiments identified that superoxide radical (•O2−) predominated in the degradation of TC-HCl by BiOBr0.7Cl0.3 MSs. And the degradation pathway and mechanism of TC-HCl by BiOBr0.7Cl0.3 MSs were proposed. What's more, the BiOBr0.7Cl0.3 MSs also exhibited considerable photocatalytic capability in the elimination of multiple fomites.

Microstructure and Corrosion Properties of Electrodeposited CoCrFeMnNi High Entropy Alloy Coatings

This study investigated the effect of potential change on the microstructure and corrosion properties of CoCrFeMnNi HEA coatings synthesized by the electrochemical deposition method. The films were precipitated in an electrolyte based on a DMF-CH3CN organic system comprising Co, Cr, Fe, Mn, and Ni cations. GIXRD pattern in all samples showed a single face-centered-cubic structure. SEM-EDS results show that the coating morphology and the elements value in alloy composition vary at different coating potentials. Coatings were uniform and crack-free surfaces. The results of the wettability test showed all coatings were super-hydrophilic. All the alloys exhibited similar passivation and negative hysteresis processes in the CPP test. However, the 5 V sample exhibited a lower Epit value than the 6 V, and none of the samples were sensitive to pitting corrosion. The CPP test result showed that the corrosion current density of the 5 V sample was 0.0525 μA/cm2, the minimum corrosion rate for the coated samples, and has improved the corrosion resistance of the substrate by about 44 times. The EIS test results showed the excellent performance of the coatings in enhancing the corrosion resistance compared to Cu substrate and similar alloy samples in a 3.5 wt% NaCl solution, as the protection efficiency was about 90%. These High entropy alloy coatings are suitable for engineering applications in which higher corrosion protection is needed.

Communication—Investigation of the Unstable Phenomenon of Electrochemical Impedance Spectroscopy Measurements for Pt Electrode in a Rotating Disk Electrode

The instability of Pt electrode during EIS measurement was investigated in RDE. Our results show that this unstable phenomenon is mainly reflected on charge transfer resistance (Rct). The range of Rct change exhibits a strong dependence on the applied potential. During the repeated EIS tests at above 0.8 V, Rct continuously increase as the testing time, while the double-layer capacitance of Pt electrode reduces, implying the formation of Pt-oxides on the electrode interface. Furthermore, the stability becomes worse at higher potential. After repeated experiment for eight times at 0.9 V, Rct increases to 3.5 times higher of the initial value.

Water-Triggered Self-Healing Composite Coating: Fabrication and Anti-Corrosion Application.

Self-healing coatings formulated by stimuli-responsive container technology are regarded as a prospective strategy for long-term corrosion protection. However, such types of coatings suffer from low coating adaptability and delays in corrosion protection because the occurrence of corrosion is prior to the release of healants from containers. Herein, we took advantage of the easy hydrolysis of MOF-199 for water-induced self-healing properties. Mixed corrosion inhibitors were loaded into MOF-199 and then incorporated into acrylic coating. The water sensitivity of MOF-199 was investigated and EIS tests were used to evaluate the self-healing performance. Due to the collapse of the porous MOF-199 structure, corrosion inhibitors could be released from MOF-199 with the invasion of water into acrylic coating. The corrosion resistance performance of damaged self-healing coating gradually increased. The metal exposed to artificial defects was well protected due to a barrier formed by corrosion inhibitors. Owing to these merits, this self-healing coating is recommended for use in various fields of engineering for corrosion resistance.

Turnip peel extract as green corrosion bio-inhibitor for copper in 3.5% NaCl solution

In this study, for the first time, we report turnip peel extract (TPE) as an eco-friendly, inexpensive vegetable waste and green bio-inhibitor for copper corrosion in 3.5 wt% NaCl solution. Ultrasound-assisted water extraction was used to prepare the TPE, and this method allows us to naturally and directly use this substance as a green inhibitor in corrosive media. GC-MS analysis was utilized to detect the main chemical compounds of TPE. EIS tests and potentiodynamic polarization techniques were used to determine the resistance of copper against corrosion in 3.5 wt% NaCl solution. SEM-EDS analysis was utilized to analyze the surface morphology and elemental identification of the copper surface. It was found that by the increment of the amount of TPE, the inhibition efficiency (IE) increased, the maximum IE was almost 92% which is promising. Also, the inhibition efficiency of TPE was studied in different corrosive solution temperatures (298–338 K) that showed the increment of temperature, reduces the inhibition efficiency, although IE is almost 64% at 338 K which is acceptable. The adsorption mechanism of TPE molecules on the copper surface is considered as physical adsorption due to the positive value of ΔH and adsorption isotherm which was matched with the Langmuir isotherm model.

Influence of SiO2 nanoparticles incorporating into ceramic coatings generated by PEO on Aluminium alloy: Morphology, adhesion, corrosion, and wear resistance

In this investigation, plasma electrolytic oxidation method was employed to incorporate SiO2 nanoparticles at concentrations of 5, 10, and 15 g/l in Al2O3 ceramic coatings on al7075. Phases, morphology and chemical composition and corrosion behavior of all specimens were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), EIS and polarization tests, respectively. A pin-on-disc test with an applied force of 10 N against 52100 steel pin was employed to evaluate the wear quality. The results showed incorporating 10 g/L of SiO2 nanoparticles modified the microstructure of coating better than other concentrations of nanoparticles and with the most closed cavities, had an adhesion strength of 47 MPa and a corrosion rate of 5.2 × 10-9 A.cm−2 which was 24 times less than that of the substrate (12.65 × 10-8 A.cm−2). In addition, 10 g/l of SiO2 nanoparticles formed a dense coating and played a role as a solid lubricant in abrasion so that it had the lowest friction coefficient and abrasion depth.

Effect of tensile stress on the corrosion performance of silicone-epoxy coatings on 2024 Al-alloy

The degradation failure of silicone-epoxy coating on 2024 Al-alloy under tensile stresses were studied by EIS and pull-out adhesion tests. The results showed that tensile stress could delay the corrosion of the coating system only in the elastic stage, but promote the corrosion of the coating system in viscoelastic stage. The water solubility was dominated by entropy effect while water diffusion was dominated by enthalpy effect. The diffusion coefficient and water uptake under tensile stress not only depends on the uneven distribution of micropores and spatial distribution of polymer chains, but also were related to the concentration of trapped water.

MoO42−-doped oxidative polymerized pyrrole-graphene oxide core-shell structure synthesis and application for dual-barrier & active functional epoxy-coating construction

Sodium molybdate (Na2MoO4) doped graphene oxide/polypyrrole nanocomposite (GO-PPy + Na2MoO4) was synthesized and considered as a multi-functional corrosion inhibitor container to be embedded into the epoxy coating. To ensure the decoration of GO surface by PPy nanoparticles and doping of molybdate ions into the GO-PPy structure, several analyses such as FT-IR, Raman, ICP-OES, zeta potential, FE-SEM/EDS, and TEM were used. The active-barrier anti-corrosion features of GO-PPy and GO-PPy + Na2MoO4 in 3.5 wt% NaCl solution were screened by EIS, salt spray, pull-off, and cathodic disbanding tests. Potentiodynamic polarization analyses showed 77% inhibition efficiency in the solution containing GO+PPy + Na2MoO4 compared to the blank solution. The GO-PPy + Na2MoO4 reinforced epoxy coating exhibited the highest impedance (log ׀Z׀10 mHz = 10.58 Ω·cm2, after 63 days) and the lowest delamination values (3.58%, after 63 days) in comparison with the pure epoxy coating (EP) (log ׀Z׀10 mHz = 6.1 Ω·cm2 and delamination value = 48.75%, after 63 days). The interaction of the NH bonds in the PPy chain with the oxide layer, and the formation of molybdate-containing compounds resulted in a considerable enhancement of the epoxy coating adhesion to the metal surface in the presence of GO-PPy + Na2MoO4.

Cage-shaped [P(W3O10)4]3- nanoclusters deposited carbon nitride to construct a dual-functional catalyst for photocatalytic mineralization wastewater and dye detector

In this work, [P(W3O10)4]-g-C3N4 composite catalyst is prepared from phosphotungstic acid and thin-layer carbon nitride at high temperature, which can efficiently remove Rhodamine B (RhB) organic wastewater by photocatalysis. The results of UV–vis, TPC, PL and EIS tests show that the introduction of [P(W3O10)4]3- increases the light absorption range of the g-C3N4 and prolongs the recombination time of photogenerated electrons and holes. The degradation efficiency of g-C3N4 and the [P(W3O10)4]-g-C3N4 catalyst are compared and analyzed, and the corresponding active species (O2·-) is proposed. The new catalyst can decolor and mineralize the RhB solution in a short time, and its degradation rate and mineralization rate are 98.0% and 81.0%, respectively. Interestingly, [P(W3O10)4]-g-C3N4 catalyst and RhB solution mixture can be used as a chili powder dye detector. Its special performance can be attributed to the dissociation of the composite catalyst under acid conditions, and the newly formed H3PW12O40 combines with the RhB solution to change color. In short, a dual-function catalyst is synthesized to remove water pollution, and its advantages such as high efficiency, rapidity and strong practicability are worthy of attention.

Influence of 2,6-dihydroxybenzoic acid on the corrosion behavior and discharge performance of AZ31 Mg alloy

The influence of different concentrations of 2,6-dihydroxybenzoic acid (2,6-DHB) on corrosion performance and discharge properties of AZ31 Mg alloy is studied by means of EIS, potentiodynamic polarization and half-cell discharge test. It was found that low concentration of 2,6-DHB (0.01 M) can enhance the corrosion resistance of Mg alloy, since it acts as complexing agent to decrease the self-corrosion rate and suppress cathodic hydrogen reaction. High amount of additive in NaCl solution accelerates the dissolution rate of the substrate, leading to deteriorated corrosion performance. The discharge properties of the Mg anode have been greatly modified by the presence of 2,6-DHB. 76.86% of utilization efficiency and 1668.17 mAh g−1 of specific capacity have been achieved for AZ31 Mg alloy in 3.5 wt % NaCl solution with addition of 0.01 M organic additive. High amount of complexing agent promotes self-corrosion and dissolution rate of the substrate, which is detrimental to the discharge properties of the anode.

Microstructure and corrosion resistance of TLPB of Inconel 625 to 316l SS

In this paper, the microstructure and electrochemical behaviour of a transient liquid phase (TLP) bonding between Inconel 625 and 316L stainless steel with a Cu interlayer were investigated. The TLP bonding was performed at 1090°C and 1120°C for 30 and 60 min. For microstructural analysis, FESEM and TEM were used. To analyse the corrosion resistance, EIS and Potentiodynamic polarisation tests in 3.5% NaCl were performed on the joint. Microstructural analysis suggested the presence of Mo–Nb, Cr–Mo and Nb-rich precipitations in the diffusion affected zone (DAZ) in the Inconel 625 side and Mo–Nb and Mo-rich precipitates in the Cu interlayer. The EIS and potentiodynamic polarisation tests showed that the highest corrosion resistance was achieved for the 1120°C-30 min sample.

Effect of channel-rib width ratio and relative humidity on performance of a single serpentine PEMFC based on electrochemical impedance spectroscopy

The geometry configuration of proton exchange membrane fuel cell (PEMFC) which is considered as a promising energy conversion device has great influence on PEMFC performance. In this paper, effect of channel-to-rib width ratio and relative humidity of reactant gas on the performance are compared based on two single PEMFCs. The EIS testing results below 50 A are given and analyzed. The results obtained from polarization curves, power density curves and EIS fitting results prove that: 1. Compared with cell 3:4, the anode high humidification has a greater addition to the performance of cell 1:1; 2. PEMFCs with different geometry configurations of flow field have their own suitable working condition ranges; 3. The charge transfer resistance is the dominating factor when current loading is below 2.0 A cm−2.

Detailed experimental investigation of the highly active corrosion inhibitive green molecules based on zinc cations/Nepeta Pogonosperma extract and toward the corrosion mitigation of mild steel in the saline solution

This work has been focused on the synergistic corrosion retardation performance (CRP) of the Nepeta pogonosperma leaves from the Lamiaceae family, which is locally called Larzeh (LA), and zinc cations (Zn2+) over the mild steel plates (MSPs) in the 3.5 wt% sodium chloride (NaCl) solution (3.5%-SCS). Different concentrations of the LA extract and Zn2+ were dissolved in the saline solutions to prepare the solution systems. The electrochemical evaluation of MSPs submerged in the solution systems was performed using EIS and PP tests. Among various ratios of LA:Zn, the 300:700 ppm LA:Zn solution illustrated the highest CRP (119.3 kΩ cm2) and efficiency (93.7%) after 12 h and was selected as the optimal solution, while the CRP values of the blank, 700:300, and 500:500 ppm LA:Zn were 1.59, 57.1, and 38.4 kΩ cm2, respectively. In the presence of 700:300, 500:500, and 300:700 ppm LA:Zn, Icorr decreased from 3.78 μA cm−2 for the blank solution to 0.372, 0.345, and 0.236 μA cm−2, respectively. WCA results proved that a more hydrophobic layer (≈55°) was formed on the MSP with 300:700 ppm LA:Zn compared to those with 700:300 (≈33°) and 500:500 (≈24°) ppm LA:Zn. The surface characterization of MSPs submerged in 300:700 ppm LA:Zn solution was carried out using FT-IR, Raman, and GIXRD analyses. Surface characterization results proved the construction of a thicker multilayer zinc-centered organic inhibitive layer by the 300:700 ppm LA:Zn extract over the MSP surface compared to other MSPs with maximum amounts of O (7.85 wt%), C (6.55 wt%), N (1.78 wt%), and Zn (20.57 wt%) elements.

High water and oxygen reactivity inducing excellent anti-corrosive performance in waterborne Ti2CTx/epoxy composite coating

The water and oxygen reactivity of MXene is one of its intrinsic characteristics, which is very detrimental in the areas including electromagnetic shielding, sensors, supercapacitors, etc. However, it plays an active role in anticorrosive coatings. In this work, few layer Ti2CTx obtained via LiF + HCl etching and ultrasonic treatment were added into waterborne epoxy coating through liquid phase blending method. They were found distributing in the coating evenly and stably. The EIS tests showed that the coating with 1.0 wt% Ti2CTx content could maintain an impedance modulus value of 108 after 21 days of immersion, which is over 2 orders of magnitude higher than that of the pure epoxy coating. The adsorption interaction effects of Ti2CTx (including the surfaces and edges) on water and oxygen were further investigated by DFT calculations. The distribution of oxidation products TiO2 in the coating were also investigated through experimental observations to analyze their corrosion protection mechanism. This study has important implications for the potential application of highly water and oxygen reactive MXene in the field of anti-corrosive coatings.

Investigating MCM-41/metal-organic framework nanocomposites as silicon-containing electrodes for supercapacitor

For both batteries and supercapacitors, developing electrodes based on Silicon is of enormous interest. The purpose of this study was to prepare two nanocomposites, MZ8 (MCM-41/ZIF-8) and MU66 (MCM-41/UiO-66), that have been specifically designed to function as electrode materials. The cyclic voltammograms showed enlarged potential window and galvanostatic charge-discharge by confirming the samples' successful synthesis process and morphological structure via XRD, FT-IR, TGA, BET, TEM, and FESEM plots gave excellent specific capacitance.MU66 with spherical morphology and average particle size around 50 nm creates more appropriate pores, and more accessible pathways showed higher capacitance (992 F g − 1 @ 0.5 Ag−1), while MZ8 (351 F g − 1 @ 0.5 Ag−1) with hexagonal morphology and average particle size around 350 nm stands more durable (100%) after 4000 cycles. MZ8 displayed an EDLC with semi-rectangular CV and symmetric charge-discharge graphs, while MU66 showed inflation at lower sweep rates and lowered current densities, representing a hybrid charge mechanism. Based on the EIS test, MZ8 showed lower charge resistance and was more conducive to taking the barriers of the low capacitance of Si-based electrodes. We believe that the fabrication of Si-containing materials into MOFs can protect Si from swelling-shrinking and maintain close contact between Si and electrolyte to use both merits of MOF structures and Si capacity.

Chemically controlled nitrogen-doped reduced-Graphene/Graphite oxide frameworks for aiding superior thermal/anti-corrosion performance: Integrated DFT-D & experimental evaluations

For the first time, via a one-pot hydrothermal synthesis method, two types of controlled edge/basal plane N-doped r-GO/graphite oxide (EDNRGO/BPNRGO) platforms were prepared using urea as a cheap, accessible, and eco-friendly precursor. The N-doping impact of the carbon structure on the GO capacity for controlled adsorption/desorption of metal cations as anti-corrosion material was assessed. The reduction degree of the GO oxygen functional groups and the nitrogen atom doping extent were analyzed via UV–Vis, Raman, XPS, FTIR, XRD, and TGA tests. The ID/IG extents resulted from the Raman test were respectively 1.02 and 1.09 for the EDNRGO and BPNRGO, indicating the higher defects for the BPNRGO sample. TGA output evidenced that the thermal stability of the graphene structures was deeply improved after nitrogen doping to 8% (EDNRGO) and 39% (BPNRGO) in comprising with pure-GO. The elemental analysis illustrated 4.87 and 7.78% nitrogen atom existence in the EDNRGO and BPNRGO samples, respectively. The above-mentioned analyses proved that the GO nitrogenation in the EDNRGO type has occurred at a lower level, and mostly in the edge of the graphene sheet than BPNRGO. The XPS test achievement confirmed the higher nitrogenation level in the BPNRGO sample than EDNRGO, recording N/C ratios of 0.061 and 0.003 for BPNRGO and EDNRGO samples, respectively. Also, it was found that most of the N-atoms were successfully inserted within the GO structure for BPNRGO. After selecting a reasonable pH range by zeta potential test, the constructed N-doped GO samples were modified by zinc ions. The corrosion inhibition activations of about 80% and 65% were obtained from the EIS test results for the Zn2+ containing BPNRGO and EDNRGO samples, respectively.

Adsorption behavior of Ti3C2Tx with h-BN nanosheet and their application in waterborne epoxy anti-corrosion coating

The addition of MXene nanosheets can significantly improve the anticorrosive properties of organic coating for its microstructure and intrinsic characteristics. But it may promote the corrosion of steel substrate for its high conductivity once forming the conductive networks. In this work, OH group modified h-BN was used to enhance the corrosion protection of waterborne Ti3C2Tx/epoxy coating and reduce the formation of the Ti3C2Tx MXene conductive networks. The B and N vacancy defects were found significantly improving the adsorption stability of Ti3C2Tx/h-BN by density functional theory (DFT) calculation, and the Ti3C2Tx/h-BN adsorption structure was observed through experiment observation. The compactness and anti-corrosion performance of composite coatings were dramatically improved after the addition of Ti3C2Tx and h-BN nanosheets. The EIS tests show that Ti3C2Tx/h-BN/epoxy coating could maintain one time constant after 21 days of immersion, and its impedance modulus at |Z|f = 0.01 Hz is over 1.5 orders of magnitude higher than that of the pure epoxy coating. This work will not only clarify the interaction mechanism between h-BN and Ti3C2Tx, but also provide a strategy for disrupting the conductive network of Ti3C2Tx.