Polarization Diagrams Research Articles

New Benzimidazole derivatives as efficient organic inhibitors of mild steel corrosion in hydrochloric acid medium: Electrochemical, SEM/EDX, MC, and DFT studies

The corrosion of mild steel (MS), a widely used material in industry, represents a significant global challenge. In order to extend the durability of equipment, the use of corrosion inhibitors proves to be an effective solution, particularly in corrosive environments. In this research, two newly synthesized benzimidazole derivatives, namely 1-(cyclohex-1-en-1-yl)-3-[(3-phenyl-1,2-oxazol-5-yl)methyl]-2,3-dihydro-1H-1,3-benzodiazol-2-one (Benz1) and 1-(cyclohex-1-en-1-yl)-3-[(3-phenyl-4, 5-dihydro-1,2-oxazol-5-yl)methyl]-2,3-dihydro-1H-1,3-benzodiazol-2-one (Benz2), were evaluated as corrosion inhibitors for MS in 1 M hydrochloric acid solution. This study was conducted using both experimental methods and computational approaches. Potentiodynamic polarization diagrams (PDP) indicate that, depending on concentration effects, Benz1 and 2 function as mixed-type inhibitors, with a predominance of cathodic inhibition. The results of electrochemical impedance spectroscopy (EIS) show that the compounds tested offer high inhibition efficiencies of 96.32 % and 98.30 % at 10−⁴ M for Benz1 and 2, respectively. Inhibitor adsorption follows the Langmuir isotherm and involves chemisorption. SEM/EDX analyses confirm the presence of a protective film on the metal. In addition, DFT and Monte Carlo simulations reveal significant adsorption of the compounds on the MS surface, underlining their high potential as effective corrosion inhibitors.

The impact of mechanical post-treatment on the tribological and corrosion behavior of CrN/CrAlN coatings applied using the CAE-PVD technique

This study examined how wet microblasting affects the tribological and electrochemical properties of CrN/CrAlN nanolayered coatings. The coatings were applied to 430 stainless steel substrates using cathodic arc evaporation (CAE), a physical vapor deposition (PVD) technique. The microblasting was performed at three different pressures (2, 4, and 6 bar) after the deposition process. Field emission SEM and X-ray diffraction techniques were employed to characterize the microstructure and morphology of the samples. The nanoscale indentation method was utilized to evaluate the indentation properties of the coatings. The tribological properties of the samples were investigated by means of a ball-on-disk tester. The coatings’ corrosion behavior was tested by EIS and PDP in a NaCl solution (3.5 wt.%). The wear results indicated that the friction coefficient decreased from 0.3 for the non-treated coating to 0.27, 0.23, and 0.5 for the coatings microblasted at 2, 4, and 6 bar, respectively. The wear resistance increased by 10 % and 23 % for the coatings microblasted at 2 and 4 bar due to the higher compressive residual stress and resistance against plastic deformation (H/E value). The EIS results revealed that the coating microblasted at 2 bar had the highest RP (2425 × 103 W cm2) and the lowest corrosion rate after 24 h of immersion in a 3.5 wt.% salt solution. The results showed that the corrosion resistance at 2 bar pressure improved approximately 16 times. The Potentiodynamic polarization (PDP) diagrams also showed that the coating microblasted at 2 bar had the lowest current density (6.3 nA cm2), indicating the highest corrosion resistance. Therefore, the optimal microblasting pressure for tribological and electrochemical applications was 4 and 2 bar, respectively.

Optimization studies of expired mouthwash drugs on the corrosion of aluminum 7475 in 1 M hydrochloric acid: Gravimetrical, electrochemical, morphological and theoretical investigations

The aim of the present work is to study the corrosion inhibition of Al 7475 alloy by an expired mouthwash drug (EMWD) in a 1 M HCl solution. The corrosion rate was optimized by the Doehlert experimental design at various temperatures, concentrations of inhibitor, and rotational velocity. The corrosion behavior was investigated by mass loss, Tafel potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. SEM, MOMT, XRD, FT-IR spectrum, and drop wettability measurement were used in characterizations of EMWD and surface morphology. Optimum conditions for corrosion control of EMWD on aluminum were 44.12 °C, 141.71 mL/L of EMWD per liter of acid, and 234.89 rpm. Maximum corrosion inhibition efficiency was 84.717% at higher levels of temperature and inhibitor concentration. It is observed that EMWD follows the Langmuir Adsorption Isotherm with negative values of ΔGadso, proposing a stable spontaneous inhibition process. The inhibitor efficiency increased as the inhibitor concentration increased. Moreover, increasing the solution temperature and rotational velocity had an adverse influence on inhibitor efficiency. The results of mass loss were in good agreement with potentiodynamic polarization and EIS. Polarization diagrams revealed that the inhibitor acts as a mixed-type inhibitor. It could be concluded that response surface Doehlert design (RSDD) was adequately applicable in the optimization of corrosion inhibition process variables and that EMWD sufficiently inhibited the corrosion of the aluminum at the studied conditions. Simulation of the EMWD molecules adsorption on the metal surface by quantum chemical theoretical studies was a powerful tool for supporting experimental outcomes.

Fabrication and characterization of incorporated nickel coatings with different loadings of tungsten carbide microparticles: Investigation of mechanical and chemical properties

This study aims to investigate the strengthening effect of incorporated nickel coatings with different weight percentages (wt.%) of tungsten carbide (WC) microparticles on the various properties of the applied coatings on plain carbon steel. Therefore, different applied coatings, including pure and reinforced nickel with various wt.% of tungsten carbide were applied to the samples using the tungsten inert gas (TIG) welding method. Then, the microstructure, wear behavior, hardness, and corrosion of the coated samples with pure and incorporated nickel with 5, 10, and 20% tungsten carbide were obtained and compared with the uncoated sample. The obtained results show that reinforcing the applied coatings with WC has improved the behavior of the coatings in different properties so that the filled coating with 20% of tungsten carbide had the best results. For example, the wear rate of coated surfaces reinforced with 5, 10 and 20% of tungsten carbide was 12.56, 7.52, and 5.28 mg/m, respectively, which was much lower than the uncoated sample with a value of 24.41 mg/m. The maximum coating hardness equal to 49.6 Rockwell C was obtained for nickel coating reinforced with 20% of tungsten carbide, which can be due to the high percentage of powder compared to other samples, and the formation of finer grains. The corrosion results of the samples using cyclic polarization diagrams showed the improvement of the corrosion behavior by adding tungsten carbide so that the nickel coating reinforced with 20% of tungsten carbide had a corrosion current density of 7.15 × 10−7 amps/cm2. Finally, the obtained results show that strengthening the applied coatings by the TIG method using different wt.% of tungsten carbide up to 20% can improve the various properties of the coating.

Investigation of the initiation and propagation of filiform corrosion on aluminum alloys by electrochemical techniques

ABSTRACT Filiform corrosion (FFC) is a type of localized corrosion commonly observed on coated aluminum alloys (AAs). Preceding research has focused on qualitative approaches of FFC on pure and binary metals. However, there is a lack of studies clarifying the FFC behaviour of commercial AAs. The present study aimed to investigate the FFC response of different AAs via electrochemical (EC) measurements. To do so, AAs 1100, 2024(Cu), 3003(Mn), 5052(Mg), 6061(Mg, Si), and 7075(Zn), were selected. Polarization measurements were carried out and three EC factors were identified from the polarization diagrams: resistance to FFC initiation (ΔEPR), driving force for propagation (ΔEcorr), and FFC kinetics (iFFC). To validate the EC results, accelerated exposure testing was performed. Coated AAs were placed in an environmental chamber and inspected; two parameters (number of threads (N) and filaments length (L)) were calculated and found to agree well with the EC factors. Results suggested that alloying elements Cu and Mg brought higher resistance to FFC initiation and slower FFC kinetics; that is, AA 2024(Cu) and 5052(Mg) showed the best resistance to FFC. In conclusion, the composition of AAs plays a significant role in their FFC susceptibility and EC measurements are effective for investigating the FFC behaviour of AAs.

Mussel-inspired polydopamine (PDA)-chitosan (CS) bio-molecules grafted graphene oxide nano-platforms synthesis and application as sustainable smart anti-corrosion system

In this paper, an innovative strategy was planned for the rational construction of a unique nanocarrier by surface modification of the GO flakes with bio-compatible/bio-degradable materials based on polydopamine (PDA) and chitosan (CS). The outcome of the TGA, UV–vis, FE-SEM/EDX, Raman, XRD, and FTIR analyses confirmed the successful adsorption of the polydopamine, chitosan, and zinc cations on the GO surface. Along with the ICP-OES and UV–vis spectra, the release of the PDA and CS molecules as well as Zn (II) ions from the GO nanolayers relies on the pH. The pH-activated release of the inhibitive compounds makes the GPCZ-containing (GO-PDA-CS-Zn) coating a suitable nanocomposite for self-healing purposes. The barrier and active corrosion protection properties of the composites in the attendance and absence of the synthesized nanoparticles were appraised by PDS and EIS techniques. The polarization diagrams disclosed that in the presence of GPCZ nanoparticles, the icorr value of the metallic substrate reduced from 4.07 (blank surface) to 0.359 μA cm−2 (GPCZ sample). The significant protection efficiencies in the scratched GPC and GPCZ/EP coatings were around 90% after 72 h denoting the active protection performance in addition to self-healing functioning. The Rct values of 0.003, 0.05, 4, 5, and 49 GΩ cm2 for the blank, GO, GP, GPC, and GPCZ coatings respectively after 77 days of immersion in the saline electrolyte show the excellent impact of the coating pigmentation in providing effective protection which inhibited the coating degradation and delamination.

Study on the influence of scale on the phase transition properties of nanoisland

Based on the transverse field Ising model, a spin 1/2 nanoisland is designed, and then the phase transition properties of the nanoisland are studied from three different scales by using the decoupling approximation of Fermi-type Green’s function, which provides some reference for possible application research. The results of phase diagram show that the change of the number of nanoisland layers does not have much effect on the phase transition properties of nano-system, and the transverse field and interlayer exchange interaction have a single effect on the phase transition properties. The results of polarization diagrams show that the polarization curves are obviously steppe when there is little difference in Js/J between lattices and there are many spin lattices. In addition, when the scale increases to a certain extent, the influence of scale on the phase transition properties of nanoisland can be ignored.

The muon pair production in the process $$e^{+}e^{-}\rightarrow e^{+}e^{-}\mu ^{+}\mu ^{-}$$ through the two-photon mechanism at high energies: transverse momentum, rapidity and angular distributions

In the present paper, we investigate the muon pair production in the interaction between two quasi-real photons in $$e^+e^-$$ collision. We calculate the total and differential cross section of the process $$\gamma \gamma \rightarrow \mu ^+\mu ^-$$ at a beam energy of photons from 3 to 40 GeV in the center-of-mass and for different values of the muon transverse momentum, the muon rapidity and the muon angle. In the $$\gamma \gamma \rightarrow \mu ^+\mu ^-$$ process we also take the contribution of the Box+Vertex correction+ Soft photon emission+Vacuum polarization diagrams. We also study the cross section of the $$e^+ +e^- \rightarrow e^+ + e^- +\mu ^+ + \mu ^-$$ process as a function of the $$e^+ e^-$$ center-of-mass energy $$\sqrt{s}$$ in the region 5 GeV $$\le \sqrt{s} \le $$ 209 GeV using the two-photon mechanism. The obtained results are in satisfactory agreement with experimental data.

Seismic anisotropy accrued by seven unusually deep local earthquakes (between 50 and 60 km) in the Albertine Rift: implications of asthenospheric melt upwelling

We investigated the primary mechanisms triggering the S-wave splitting (SWS) of seven unusually deep local earthquakes (between 50 and 60 km) which originated in the lithosphere beneath the Rwenzori region. We attempted to develop an understanding of the relationship between anisotropic structures in the lithosphere and tectonic deformation processes. A total of 12 out of 44 waveforms showed evidence of SWS on their polarization diagrams. The fast-wave direction (φ) and delay-time (δt) were estimated using the covariance matrix and the cross-correlation coefficient methods, respectively. We observed a clockwise rotation of φ-directions (NW - SE and ~ENE - WSW) at stations located in the rift valley. We related this pattern of φ-directions to anisotropic fabric, probably lattice-preferred orientation of preexisting olivine, whose a-axes are aligned with ESE absolute plate motion (APM) vector. At stations located outside the rift valley, however, we observed WNW - ESE and NNW - SSE patterns of φ-directions. We associated these patterns to the shape-preferred orientation of structures frozen in the lithosphere that are aligned with the present-day APM direction. We observed δt values ranging between 0.04 ± 0.01s and 0.43 ± 0.02 s, which decrease with distance away from the rift axis. This further supported our concept that the anisotropy observed at stations located on the moving plate is related to aligned melt inclusions frozen in the surrounding lithosphere. We further observed that the δt values increase linearly with ray-path length, which could indicate a fairly uniform anisotropy between 50-km and 60-km depth. Our study reported no evidence of multi-layer anisotropy beneath the Rwenzori region.

Electrochemical mechanism of metall corrosion

Corrosion that occurs by an electrochemical mechanism is a combination of cathodic and anodic reactions that occur independently of each other. At that, the metal surface is considered to be equipotential one, i.e. the presence of short-circuited microgalvanic pairs on the surface is not a necessary condition for electrochemical corrosion. The anode and cathode processes are spatially separated. This is provided by the presence of conduction electrons in the interstitial spaces of the metal lattice. The present model of electrochemical corrosion justifies the use of polarization diagrams for the analysis of corrosion processes. The previously proposed model, based on the idea that a necessary condition for electrochemical corrosion is the presence of short-circuited microgalvanic elements on the metal surface, is erroneous. When considering electrochemical corrosion from the positions of this model, the use of polarization diagrams to study corrosion processes is not legitimate.

Hierarchical nanostructures of MgCo2O4 on reduced graphene oxide as a high-performance catalyst for methanol electro-oxidation

A flower-like binary transition metal oxide, in the form of MgCo2O4, was successfully synthesized and investigated by XRD and Raman spectroscopy as well as by SEM and TEM micrographs. A hybrid of MgCo2O4 with reduced graphene oxide (rGO) was prepared to distinguish between the rGO-riched and rGO-free catalysts for potential applications in direct methanol fuel cell (DMFC) anodes (methanol electro-oxidation process). The synergetic effect due to the proximity of magnesium and cobalt oxides, along with their hybridization on the rGO, makes MgCo2O4-rGO an efficient and low-cost catalyst for an anode electrode in the DMFC applications. EIS, CV, LSV tests, and cyclic stability of MgCo2O4-rGO for 2000 subsequent CV cycles confirm the pivotal role of rGO in the catalyst structure. Finally, the single-cell test indicated the suitability of our proposed catalyst for practical applications of DMFC. Indeed, the single-cell polarization diagrams show a significantly improved power density for single cells with MgCo2O4-rGO-based anode (19 mW cm−2) compared to MgCo2O4- based anode (11 mW cm−2).

Stevioside–Zn2+ system as an eco-friendly corrosion inhibitor for C1020 carbon steel in hydrochloric acid solution

An effective and biodegradable Stevioside from Stevia leaf was evaluated as a potential pickling inhibitor in combination with the Zn2+ cation for C1020 carbon steel (CCS). Considering its naturally occurring, cheap and environmentally safe properties, Stevioside has the potential to be widely used to inhibit the CCS corrosion in HCl solutions. The corrosion inhibition performances of Stevioside and Stevioside–Zn2+ were studied with the use of weight loss test, electrochemical techniques, and surface analysis methods. The results demonstrated an incorporation of Zn2+ component into the Stevioside layer can evidently improve the uniformity and anti-corrosion properties (i.e., 76.59 % versus 95.68 %). The optimal molar ratio of Stevioside/Zn2+ was found to be 1:2, and the highest inhibition efficiency was 95.68 % evidenced by electrochemical test. Polarization diagrams revealed that the Stevioside and Stevioside–Zn2+ behaved as mixed type inhibitors and mainly inhibited the anodic process. The surface morphology by SEM, SECM and XPS confirmed the effectiveness of the inhibitor. Molecular dynamics simulations disclosed that the inhibitor retard the CCS corrosion during the descaling process through the mechanism donor-acceptor interaction.

Apostichopus japonicus polysaccharide as efficient sustainable inhibitor for mild steel against hydrochloric acid corrosion

A bio-friendly polysaccharide from Apostichopus japonicus (AJPS) was evaluated as a potential inhibitor using weight loss test, electrochemical investigations, SEM and AFM methods. Weight loss measurement exhibited the percentage inhibition efficiency of 96.03% for AJPS and in the optimum concentration of 625 mg/L at 35 °C. Polarization diagrams revealed that the AJPS behaved as a mixed type inhibitor and mainly inhibited the anodic process. The inhibition performance of AJPS was optimized by factorial experimental designs, the optimized conditions for the minimum corrosion rate were CAJPS = 625 mg/L, t = 7 h, T = 35 °C. surface morphology by SEM and AFM confirmed the effectiveness of the inhibitor. Density functional theory (DFT) disclosed that the electron donor (EHOMO) and electron acceptor (ELUMO) of AJPS forms strong chemical bonds with the vacant d-orbital of mild steel surface

Experimental and theoretical studies of a novel synthesized azopyrazole-benzenesulfonamide derivative as an efficient corrosion inhibitor for mild steel

Herein, a novel inhibitor for the mild steel corrosion in an acidic environment based on azopyrazole-benzenesulfonamide derivative, namely 4-(2-(3-methyl-5-oxo-1-tosyl-1H-pyrazol-4(5H)-ylidene) hydrazinyl)-N-(pyrimidin-2-yl) benzenesulfonamide, is investigated. The electrochemical tests were performed using open-circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy. Furthermore, the corrosion inhibition mechanism is explained using Tafel polarization and Langmuir isotherm. The obtained findings revealed that corrosion resistance effectiveness increased as the resistant concentration grows. Moreover, Tafel polarization diagrams indicated that the compound used is a mixed-form inhibitor. The chemically quantum factors have been determined using the density functional hypothesis. A good correlation between the experimental findings and theoretical predictions is found from all the results of this study. In addition, the proposed corrosion inhibitor can be used for a wide range of industrial applications due to the high inhibition efficiency.

3-Methoxypropyl-amine as corrosion inhibitor for X80 steel in simulated saline water

The inhibition of X80 steel corrosion by a 3-Methoxypropyl-amine (MOPA) as a new corrosion inhibitor in saline solution (3.5 wt% NaCl) was optimized at different temperatures, inhibitor concentrations, the rotation speed of the solution and pH. Mass loss and polarization measurements were used to evaluate the corrosion rate and other kinetics parameters. The inhibition performance of MOPA was optimized by factorial experimental designs. Optimum conditions for the minimum corrosion rate were 12.89 °C, 8.63 g/l, 1097.69 rpm, pH 4.03. It was observed that MOPA follows the Langmuir adsorption isotherm with negative values of ΔGadso, proposing a spontaneous and stable inhibition process. According to ΔGadso values, a physical adsorption was suggested. The inhibitor efficiency increased with increasing the inhibitor concentration and pH of the solution. Moreover, increasing the solution temperature and rotation velocity had an adverse influence on inhibitor efficiency. Results of mass loss technique were agreed with the polarization one. Polarization diagrams revealed that the inhibitor affects as a mixed-type inhibitor. Surface morphology and FTIR spectrum studies were confirmed the effectiveness of the inhibitor. A theoretical quantum chemical simulation was a powerful tool for the optimization of the MOPA structure.

Protection of fuel filter with alkaline and acid zinc coatings

Galvanic coatings are applied so that the surface of the base material obtains appropriate properties, corrosion resistance, durability, aesthetic appearance, and long-term application in the appropriate industry. In this paper, the aim was to protect steel fuel filters with alkaline and acid zinc coatings of different thicknesses. The coating of zinc, which is applied from the alkaline electrolyte, provides good corrosion protection with excellent coating flexibility. The thickness of the coating by the X-ray fluorescence method was tested, followed by coating tests, corrosion resistance, and electrochemical tests. The results of adhesion showed a high quality coating, as no corrosion occurred during the test. The corrosion resistance tested by the salt chamber method speaks of the appearance of white and red corrosion. On alkaline electrolyte coatings, white corrosion occurred after 168 hours of exposure to the salt test, while on white zinc samples there was a white corrosion after 240 hours of exposure. Tafel polarization diagrams have been determined: corrosion potentials, current intensities, anode and cathode Tafel coefficients and calculated corrosion rates. The active and passive corrosion zone is determined by the cyclic voltammetry.

A Study of Galvanic Corrosion in Stagnant Ammonium Bisulfide Solution

Galvanic corrosion of carbon steel (CS) coupled to four different alloys, namely, 316 SS, 321 SS, Incoloy 825, and 2205 SS, was studied in deaerated 3.5% ammonium bisulfide solution (ABS) at 60°C by electrochemical techniques under stagnant condition. The electrochemical work included the measurements of the potential of separate alloys as well as the measurements of galvanic potential and galvanic current as a function of time and Evans (polarization) diagrams of coupled metals. The impact of galvanic coupling on the anodic and cathodic reaction rates was determined. It was found that the CS suffered galvanic corrosion when it was coupled to all of the selected alloys but at different rates; so, it is recommended to avoid the galvanic coupling of CS with any of the noble alloys in stagnant deaerated 3.5% ABS at 60°C. Results indicated that the best alloy to be used with the CS in stagnant deaerated 3.5% ABS solution at 60°C is SS 2205 since the galvanic couple has the lowest CR with a less negative Ecorr value, indicating that CS corrodes at a lower rate when it is coupled to SS2205 in this environment.

Fixed volume effect on polar properties and phase diagrams of ferroelectric semi-ellipsoidal nanoparticles

For advanced applications in modern industry, it is very important to reduce the volume of ferroelectric nanoparticles without serious deterioration of their polar properties. In many practically important cases, the fixed volume (rather than the fixed size) corresponds to realistic technological conditions of nanoparticles fabrication. The letter is focused on the theoretical study of the behavior of ferroelectric polarization, paramagnetoelectric coefficient and phase diagrams of semi-ellipsoidal nanoparticles with a fixed volume V. Our approach combines the Landau-Ginzburg-Devonshire phenomenology, the classical electrostatics, and the elasticity theory. Our results show that the size effects on the phase diagrams and polarization of semi-ellipsoidal BiFeO3 nanoparticles nontrivially depend on V. These findings provide a path to optimize the polar properties of nanoparticles by controlling their phase diagrams at a fixed volume.

Spin related transport in two pyrene and Triphenylene graphene nanodisks using NEGF method

The present study is conducted to evaluate the spin polarization in two pyrene and Triphenylene graphene nanoflakes. All calculations are performed using non-equilibrium Green's function (NEGF) method. The obtained results show that, graphene has no magnetic property and using Pyrene nanoflake results in a better spin switching at extreme magnetic fields. On the contrary, when applying magnetized electrodes, depending on the direction of magnetization of the two electrodes (either parallel or anti-parallel), different spin polarization diagrams are obtained. In this situation, it is observed that, in the case of electrodes magnetization in Triphenylene nanoflake a better spin switching is reached.

The effect of Al2O3 nanoparticles on tribological and corrosion behavior of electroless Ni–B–Al2O3 composite coating

In this study, the Ni–B–Al2O3 composite was successfully coated on the surface of Ck45 steel by elecroless method. X-Ray diffraction analysis (XRD) and scanning electron microscopy (SEM) were utilized in order to investigate and identify the coating properties. Wear behavior of the coating was studied by the pinon- disk test. Corrosion behavior of the Ni–B and Ni–B–Al2O3 coatings was investigated by using Tafel polarization diagrams in the 3.5% NaCl solution at room temperature. The obtained data demonstrate that the addition of Al2O3 nanoparticles to the coating has resulted in improving the tribological behavior of the coating due to the presence of the composite nanoparticles. Also, the results of electrochemical testing show that corrosion resistance of the electroless Ni–B coating with Al2O3 nanoparticles has dramatically increased.