Tafel Polarization Curves Research Articles

An Environmentally Friendly Yellow Composite Pigment: Leaching Stability and Corrosion Inhibition Properties

AbstractThe novel PbCrO4‐based composite pigments, X‐PbCr/CHAP (X=10, 30, 40, 50), consist of different weight percentages of PbCrO4 and carbonate hydroxyapatite (CHAP) were synthesized by sequence precipitation‐calcination process. These pigments showed significantly higher leaching stability compared with PbCrO4. Electrochemical impedance spectroscopy and Tafel polarization curves were used to investigate the corrosion efficiencies of the pigments. The obtained results clearly demonstrated the inhibitive action of X‐PbCr/CHAP pigments. The composite pigments showed higher corrosion resistance compared with pure PbCrO4 due to the formation of phosphate and calcium hydroxide species as a passive layer over the surface of the steel.

Vinyl ester/silica aerogel nanocomposite coatings with enhanced hydrophobicity and corrosion protection properties

AbstractVinyl ester (VE) resins have been widely used in the coating industry. However, research on its potential in anti‐corrosion applications has been limited. In this work, silica aerogels were first synthesized and then incorporated into the VE resin at 5, 10, and 15 wt% with respect to the VE content. Based on the morphological results, higher inclusions of silica aerogels (10 and 15 wt%) were significantly aggregated at the surface layer of the coatings leading to a highly rough surface structure which was also proved by atomic force microscopy. In fact, the aerogel nanoparticles formed a very packed structure leading to the formation of an effective physical barrier against corrosive agents. Fourier‐transform infrared spectroscopy also revealed that the nanocomposite coatings exhibited a lower water absorption behavior which could be beneficial for the anti‐corrosion behavior. Wetting results demonstrated that the water contact angle has essentially increased from 61° for the pure VE coating to 92° for the aerogel‐loaded coating. Such enhancement in hydrophobicity and also the creation of a physical barrier at the surface layer of the coatings led to promising barrier results as found by Tafel polarization curves. The protection efficiency was dramatically improved to 97.9% for the highest inclusion of silica aerogel.

In situ solvothermal growth of Cu2ZnSnS4 thin film for counter electrode of dye-sensitized solar cells

Quaternary Cu2ZnSnS4 (CZTS) nanocrystalline thin films were in situ grown on FTO coated conductive glass by a low cost solvothermal method. The effect of the reaction time and the concentration of precursor solution on the purity and morphologies of the deposited thin films was studied. The morphology, crystal structure and composition of the deposited thin films were characterized by scanning electron microscope, high resolution transmission electron microscope, X-ray diffraction, Raman spectroscopy and energy-dispersive X-ray spectroscopy. The pure wurtzite CZTS nanoparticles can be formed as the reaction time is 20 h. The film prepared at the optimized precursor solution concentration has uniform thickness, smooth surface and tight binding between the nanoparticles. The performance of the deposited CZTS thin films used as the counter electrode for dye-sensitized solar cells (DSSCs) was evaluated by measuring photocurrent density-voltage curves of DSSCs, electrochemical impedance spectroscopies and Tafel polarization curves of the symmetric cells. Photoelectric conversion efficiency of DSSC based on the optimized CZTS counter electrode reached 6.19%. The excellent photoelectric performance is attributed to the better surface morphology and conductive skeleton of the prepared CZTS thin film. The in situ solvothermal preparation method of the CZTS thin films for counter electrode of DSSCs is green, low cost and simple.

Effect of the sample form on the corrosion behavior of steels for concrete in 3% NaCl medium

Corrosion of steel constitutes a major preoccupation in the field of civil engineering and the building sector. In this paper, we investigated the electrochemical behavior of two steel specimens with different forms (latched steel and smooth steel) in a 3 wt.% NaCl solution. For this purpose, we studied the steel samples by linear polarization, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The surface morphologies of the substrates were examined by scanning electron microscopy coupled with energy diffraction spectroscopy (SEM/EDS). Results of linear polarization, Tafel polarization curves and EIS show that latched steel (LS) is more susceptible to corrosion than smooth steel (SS) in saline solution. Gravimetric and SEM/EDS analysis after 10 days of immersion confirmed the results obtained by electrochemical methods. All of our results are in agreement and demonstrate that the sample form plays a key role in corrosion resistance.

Ethanol extract of waste potato peels for corrosion inhibition of low carbon steel in chloride medium

Abstract Corrosion of low carbon steels is a big constraint in their smooth use for engineering applications. Corrosion not only destroys their designed properties but also harms their physical appearance. Several researchers are working to minimize the effect of corrosion on low carbon steel. In this regard, they have consumed a lot of synthetic and natural materials till date. Nowadays, researchers are showing their trust on natural materials for corrosion inhibition application due to their easy availability, negligible toxicity and easy synthesis process as well as eco-friendly nature. It is an established fact that waste natural materials (WNMs) like banana peels have very high potential for being used in corrosion inhibition application due to their bioactive contents. However, WNMs have not been explored frequently by the researches despite their supreme technical and economical importance in corrosion inhibition. In this work, ethanol extract of waste potato peels is used for corrosion inhibition of low carbon steel in 0.5 M NaCl. The inhibition properties of the extract are determined by weight loss measurements, open circuit potential (OCP) curves, electrochemical impedance spectroscopy (EIS), Tafel polarization curves and linear polarization resistance (LPR) techniques. Results show that maximum corrosion inhibition efficiency of 70% has been achieved using 1000 mg L−1 of the extract. Scanning electron microscopy (SEM) and energy dispersive X-RD Spectroscopy (EDX) has also shown that the extract has successfully protected low carbon steel in 0.5 NaCl.

Waste Solanum melongena stem extract for corrosion inhibition of mild steel in 1M NaCl

Abstract Corrosion of metals is a serious problem for the economy and human lives of any country. Several researchers have been working to minimize the loss of corrosion damage. Green corrosion inhibitors (GCI) are a simple solution of the corrosion problem since GCI is non– toxic, efficient in corrosion inhibition, biodegradable and available at low cost. In this regard waste natural materials (WNM) have attracted a great attention of the scientists since their use as corrosion inhibitors is economic, safe and eco-friendly (recycling of the waste). In this work, Solanum melongena steam (brinjal cap) aqueous extract (SMSAE) is used for corrosion inhibition of low carbon steel (LCS) in 1 M NaCl. The extract is characterized by Uv–visible and FTIR spectroscopy, which suggest that the extract is electrochemical active. The corrosion inhibition properties of the extract was determined by weight loss measurements, electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) curves and Tafel polarization curves (TPC). The results show that the extract is giving inhibition efficiency > 70% at 500 mg L-1 of the extract. Surface and compositional analysis was performed by Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, which evidently illustrate that the extract is successfully inhibiting corrosion of mild steel in 1 M NaCl. It can be said based on results that SMSAE (WNM) is providing good inhibition efficiency and can be used in different applications.

Effect of La Addition on the Microstructure and Properties of Al-Fe-Mn Alloys for Lithium Battery Current Collectors

Good electrical conductivity, mechanical properties and electrochemical performance are required for aluminum alloys acting as cathode current collectors of lithium ion batteries (LIBs). The effect of La alloying on the microstructure, mechanical properties and the electrochemical performance of Al-Fe-Mn alloys were characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, tensile test, conductivity test and Tafel polarization curve test. The experiment results showed that Al13Fe4 and Al6(Mn, Fe) precipitates tended to nucleate and grow along the grain boundaries. The addition of La to the Al-Fe-Mn alloy could help to refine grains and spheroidize secondary phases. These changes in microstructure could improve the tensile strength and elongation at room temperature and a high temperature of 125°C and enhance the corrosion resistance of the alloy. However, the spheroidized precipitates tended to aggregate in the alloy with 0.15 wt.% La and this uneven aggregation resulted in a decrease in tensile strength and elongation in comparison to the alloy with 0.1 wt.% La, which suggested an optimal La content for the Al-Fe-Mn alloy.

Preparation of cobalt–manganese-modified lead dioxide anodes and the study of their electrochemical performance in electrowinning copper

The anode materials PbO2–MnO2, PbO2-CoOx, and PbO2–MnO2-CoOx, were prepared by anodic oxidation in the nitrate system. The microstructure and chemical composition of the anode materials were characterized by scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of the anode materials were studied by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and Tafel polarization curves (Tafel). The results indicate that the coating of PbO2–MnO2-CoOx anode materials with a spherical structure, and the PbO2–MnO2 and PbO2-CoOx anode materials with a stacked pellet structure. Compared with PbO2, PbO2–MnO2, and PbO2-CoOx anodes, PbO2–MnO2-CoOx anodes have the maximum exchange current density (j0) values, the minimum charge transfer resistance (Rct) values, and minimum the self-corrosion current density (icorr) in electrowinning Copper solution. The cell voltage of Cobalt-containing Manganese anode material is lower than that of traditional Pb–Sn–Sb anode material, Indicating that the Cobalt-containing Manganese anode material is of practical value to reduce energy consumption.

The microstructures and corrosion behavior of cladding layer on Ti-6Al-4V alloy using arc deposition with Ar and CO2 mixed shield gas

The surface modification of Ti6Al4V in biomedicine aims at the regeneration and healing of bones. It prolongs the service life, which is the basic understanding of friction and corrosion occurring at the biomaterial/human fluid interface. To modify the Ti6Al4V surface, CO2 was added to the shielding gas during the arc cladding process so that the strengthening phase TiOx and TiC were obtained in the cladding layers. A continuous cladding layer is obtained on the surface of Ti6Al4V without any pores and slag inclusions. After adding CO2 in the shielding gas, a large amount of TiOx and TiC are obtained in the cladding layers. As the amount of TiOx phase and TiC phase increases in the cladding layer, the microhardness gradually increases from 350HV to about 600HV. The effect of electrochemical corrosion of different cladding layers was studied in 3.5% NaCl solution using tafel polarization curves and electrochemical impedance spectroscopy(EIS). With the increase of the CO2 flow rates in the shielding gas, the value of Icorr gradually decreases from (5.12 ± 1.1) × 10−8 A/cm2 to (2.45 ± 0.5) × 10−8 A/cm2, and the pits on the corroded surface are gradually reduced, which indicates that the corrosion resistance of the cladding layers is gradually improved.

Electrochemical behavior of two dyes as corrosion inhibitors for carbon steel in acid medium and studying their biological activities by practical and theoretical aspects

The inhibitive action of azo dye aminophenol derivatives, namely 6-(4-benzenesulfonic acid azo)-3-aminophenol (compound (1)) and 4-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-3-aminophenol (compound (2)) against the corrosion of C-steel in 2 M HCl solution using Tafel polarisation, surface morphology, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. The inhibition efficiency increased with increasing inhibitor concentrations and decreased with increasing temperature. Tafel polarization curves showed that the corrosion rate was decreased with increasing compounds concentration into HCl solution. Inhibition efficiency values obtained from various methods employed were in reasonable agreement. It was found that the order of % IE of these investigated compounds obey the following order: compound (2) > compound (1). Also, the antimicrobial and antifungal activities of the aminophenol derivatives compounds (1 and 2) and comparing them with the standard antibacterial and antifungal drugs were described. The results showed that the compound (2) is very good antibacterial agents against Bacillus subtilis and Staphylococcus aureus. The compound (2) is more active than the compound (1) and penicillin G against Bacillus subtilis and Staphylococcus aureus. It was found that the compound (2) is more active than penicillin G which is used as the antibacterial standard drug against Enterobacter sp. and Klebsiella pneumoniae. Molecular docking was used to predict the binding between aminophenol derivatives compounds (1 and 2) and the receptors of the crystal structure of Staphylococcus aureus (3q8u) and the crystal structure of Escherichia coli (3t88). The compound (2) showed best interaction with receptor of Staphylococcus aureus (3q8u) than the compound (1).

Evaluation of the corrosion inhibitory effect of Napoleonaea Imperalis leaf extract on mild steel in a 1.3 M H2SO4 medium

The study investigated the corrosion inhibitory effect of Napoleonaea imperalis leaf extracts (‘NI’) on Mild steel (M-steel) in 1.3 M H2SO4. Weight loss, potentiodynamic and electrochemical impedance spectroscopy (EIS) at 303 K–343 K were the investigative approaches adopted in the study. The resultant oxide from the study was characterized using Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscope (SEM). Meanwhile, the experimental results were validated using theoretical calculations. The experimental findings showed that by increasing the inhibitor concentration (from 0.2 to 1.0 g/L) at a low operational temperature of 303 K, an increased inhibition efficiency (from 47.93 to 85.54%) was observed. The organic functional groups responsible for inhibition effect were identified in the FTIR result. Similarly, the SEM result showed the occurrence of significant transformation on the M-steel surface due to effective corrosion inhibition by ‘NI’. The range of values of the free energy of adsorption, ∆Gads (− 12.88 to − 5.83 kJ/kmol) and heat of adsorption, Qads, (− 24.10 to − 5.10 KJ/kmol) indicates the occurrence of physisorption process. The negative values obtained for the free energy of adsorption is an indication for a spontaneous and exothermic inhibition process. Tafel polarization curves depicted the inhibitor used in the study as a mixed-type. Similarly, the density functional theory (using molecular dynamic simulations) suggested a dependent adsorption process with coordinate bonds via metal/inhibitor interface. The study succinctly demonstrated an excellent inhibition performance of ‘NI’ in M-steel corrosion.

An electrochemical method to investigate the effects of compound composition on gold dissolution in thiosulfate solution

AbstractThe electrochemical behavior of gold dissolution in the Cu2+–NH3–S2O32−–EDTA solution has been investigated in detail by deriving and analyzing the Tafel polarization curve, as this method is currently widely implemented for the electrode corrosion analysis. The dissolution rate of gold in Cu2+–NH3–S2O32−–EDTA solution was determined based on the Tafel polarization curves, and the effects of various compound compositions in a Cu2+–NH3–S2O32−–EDTA mixture on the corrosion potential and corrosion current density were analyzed. The results showed that the corrosion potential and polarization resistance decreased, whereas the corrosion current density increased for certain concentrations of S2O32−–NH3–Cu2+and EDTA, indicating that the dissolution rate of gold had changed. The reason for promoting the dissolution of gold is also discussed.

Comprehensive performance test and analysis of graphene-enhanced chromium-free Dacromet coating

Abstract The proposed work aims to improve the comprehensive properties of the composite coating by adding different content of graphene into the coating solution. Firstly, the formulation of the coating solution was determined by the L16(45) orthogonal test. Secondly, the conventional properties of the coating were tested using the optical microscope and micro-vickers hardness tester. Thirdly, the corrosion resistance of the coating was tested by the rapid ammonium nitrate corrosion test, immersion test, and neutral salt spray test. The changes of the microstructure and composition of the coating before and after corrosion were observed and analyzed using the scanning electron microscope, energy dispersive spectrometer, X-ray diffractometer, and Raman spectrometer, and the Tafel polarization curves and electrochemical impedance spectroscopy of the composite coatings with different graphene contents were tested by electrochemical experiments. The results show that the hardness of the coating increases with the increase in the content of graphene. Graphene intercalates between zinc and aluminum powders in a flaky structure, which reduces the appearance of voids and enhances the protection of chromium-free Dacromet coatings, slows down the penetration of electrolyte solutions and effectively slows down the penetration of corrosive media. The addition of a small amount of graphene can increase the corrosion potential and decrease the corrosion current density of the chromium-free Dacromet coating, the Nyquist low frequency of the coating is higher in the same period and the salt spray resistance of the coating is the best.

Reduced graphene oxide/silica nanocomposite‐reinforced anticorrosive fluorocarbon coating

AbstractReduced graphene oxide‐silica (rGO/SiO2) nanocomposite filler was prepared with a ball milling process and then modified using a coupling agent of NH2C3H6Si(OC2H5)3(KH‐550) to improve its dispersion in the fluoroethylene vinyl ether (FEVE) coating. The surface properties and morphologies of the modified rGO/SiO2(M‐rGO/SiO2) nanocomposite filler and M‐rGO/SiO2‐reinforced FEVE coating were characterized by using Fourier transform infrared spectroscopy (FT‐IR) and scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and Tafel polarization curves were applied to illustrate the corrosion resistance of the coating. The results showed that the M‐rGO/SiO2composite can disperse well in the coating and efficiently extend the corrosion path, enhancing the anti‐corrosion property of the FEVE coating. Therefore, the |Z|0.01 Hzof M‐rGO/SiO2reinforced FEVE coating maintained at around 1010 Ω·cm2in the 30 days test cycle and a protection efficiency of up to 95.18% was achieved.

Corrosion Inhibition and Passivation Delay Action of Lauroamide Propylbetaine on Zinc in Alkaline Medium

The effects of lauroamide propylbetaine on zinc corrosion and passivation are investigated in 7.0 M KOH solution saturated with ZnO by Tafel polarization curve, electrochemical impedance spectroscopy and linear sweep voltammetry. It demonstrates that lauroamide propylbetaine acts as cathodic-type inhibitor and restrains zinc corrosion in alkaline medium through reducing the hydrogen evolution. With increasing concentrations of lauroamide propylbetaine, the corrosion inhibition effect and charge transfer resistance of zinc electrode enhance, and the corrosion inhibition efficiency reaches up to 84.1% in the presence of 800 ppm lauroamide propylbetaine. It is confirmed that the adsorption of lauroamide propylbetaine on the surface of zinc electrode follows Langmuir isotherm model. Besides, anodic polarization curves suggest that a small quantity of lauroamide propylbetaine is advantageous to delay the passivation of zinc electrode. Results reveal that the corrosion of zinc surface is alleviated in alkaline medium in the presence of 800 ppm lauroamide propylbetaine.

High-efficiency photoelectrochemical cathodic protection performance of the iron-nitrogen-sulfur-doped TiO2 nanotube as new efficient photoanodes

Novel iron-nitrogen-sulfur-tridoped titanium dioxide nanotubes (Fe-N-S-TiO2 NTs) have been synthesized via single step anodization of titanium using potassium ferricyanide, as a suitable additive, in dimethyl sulfoxide (DMSO) electrolyte and applied as photoanodes in the photocathodic protection of stainless steel 403 (SS403). Photocurrent density, open circuit potential and Tafel polarization curves have been used to study the photocathodic protection effect of the samples prepared. Upon the addition of potassium ferricyanide to the anodizing electrolyte and titanium dioxide nanotube doping, the light absorption of the Fe-N-S-TiO2 NTs were increased to the visible region, comparable with pure TiO2 NTs, according to the results obtained. Enhanced photoelectro-response activity and photocathodic protection performance for 403 stainless steel are exhibited by Fe-N-S-TiO2 NTs under light illumination. In addition, the optimal sample electrode (FT4) potentials shifted negatively to −683 mV under illumination.

Lemon seeds as green coating material for mitigation of mild steel corrosion in acid media: Molecular dynamics simulations, quantum chemical calculations and electrochemical studies

Natural materials are the subject of high priority for corrosion scientists, now a day. Various natural materials have been used to date for corrosion protection of metals. However, their utilizations have been done either in inhibition (mostly) or coating applications (only in composite form). In present work, lemon seed (alone) is used for inhibition as well as coating protection of mild steel (MS) corrosion in acid media. Aqueous extract of lemon seed (ALS) is used as inhibitor, whereas chloroform extract of lemon seed (CLS) is used to form wet (CLSW) and dry (CLSD) coating on MS substrate. Characterizations of ALS, CLSW and CLSD have been done by UV–visible spectroscopy, FTIR spectroscopy, HRSEM, EDAX and AFM analysis. Corrosion testing of both extracts has been performed in 1 M HCl by ac impedance measurements (AIM) and Tafel polarization curves (TPC). The results show that ALS gives very low inhibition of MS corrosion (~45%), while MS coated with CLSD/CLSW provide high efficiency protection (~98%) to the substrate. Theoretical analysis tools, i.e., molecular dynamics simulations and quantum chemical calculations, are also used to determine corrosion properties of lemon seed molecule, which suggest that lemon seed can be prominent material for prevention of MS corrosion.

Ammonium thiocyanate functionalized graphene oxide-supported nanoscale zero-valent iron for adsorption and reduction of Cr(VI)

In this study, ammonium thiocyanate functionalized graphene oxide (ATGO)-supported nanoscale zero-valent iron composite (ATGO-nZVI) employed to extract Cr(VI) from aqueous solution, was successfully synthesized by chemical oxidative polymerization and sodium borohydride reduction method. Characteristics of X-ray diffraction and high-resolution transmission electron microscopy confirmed the high disperse and activity of nZVI after supported by ATGO. Batch experiments showed that the removal efficiency of ATGO-nZVI was higher than that of bared nZVI and ATGO. Furthermore, the stability of ATGO-nZVI composite was higher than that of nZVI, which was proved by the Tafel polarization curves. Dynamic experiments suggested that the removal process was confirmed to be in agreement with not only the pseudo-second-order model for adsorption but also Langmuir-Hinshelwood first-order model for reduction process, which revealed that the removal of Cr(VI) by ATGO-nZVI composite was dominated by chemical surface-limiting step. Considering the experiments and characterization, the removal mechanism containing rapid adsorption of Cr(VI) onto the ATGO-nZVI surface and reduction by nZVI was clarified. The above results suggested that ATGO-nZVI would become a promising remediation material for Cr(VI) pollution cleanup.

PRODUCTION AND PROPERTIES OF COMPOSITE ELECTROCHEMICAL COATINGS WITH ELECTROCHEMICALLY DISPERSED GRAPHENE BASED ON NICKEL MATRIX

In this work, the effect of addition of colloidal solutions of electrochemical exfoliated graphene (EEG) to the Watts bath on the process of obtaining composite coatings based on a nickel matrix was studied. It was found that the introduction of nanoparticle additives has a significant effect on the value of cathodic overvoltage during electro reduction of Ni2+. The strongest inhibition of the cathode process takes place with the introduction of 0.2 g/l of additives investigated. Further increase in the concentration of nanoparticles in the bath reduces the effect. The inhibition of the cathodic reduction of Ni2+ is associated with the adsorption of graphene nanoparticles on the active faces of growing nickel crystallites and the blocking of the accessible surface for Ni2+ reduction. Due to the increase in cathodic polarization during the deposition of the composite coating, the crystallites of the deposited nickel decrease in size and the texture of the crystal structure of the coating changes. According to energy dispersive spectroscopy data, carbon has been included in the composite coating. The carbon content in the coating increases with increasing concentration of nanoparticles in the working electrolyte. The inclusion of negatively charged nanoparticles of electrochemically dispersed graphene in the resulting precipitate becomes possible due to adsorption of Ni2+ and recharging of graphene nanoparticles. It was found that the optimal concentration of electrochemically dispersed graphene in the working electrolyte is 0.1-0.2 g/l. At a given nanoparticle content in the working bath, the porosity and roughness of the coatings decreases. The Tafel polarization curves for composite coating samples obtained in a 0.5M NaCl solution showed that the inclusion of graphene nanoparticles in the resulting coating leads to a shift of the corrosion potential to the negative area. With an increase in the carbon content in the coating, the shift in corrosion potentials increases, and the value of corrosion currents increases. For samples of composite coatings obtained at an EEG additive concentration of 0.1 g/l, a slight improvement in the protective properties is noted, which is associated with a decrease in the porosity of the coatings.

Superhydrophobic surface based on nano-engineering for enhancing the durability of anticorrosion

ABSTRACT Here, a new class superhydrophobic surface based on nano-engineering was proposed and prepared to improve the durability of corrosion protect. Moreover, the durability of anticorrosion was evaluated by the Tafel polarization curves and electrochemical impedance spectroscopy under various damages of mechanical abrasion, chemical immersion and cool/thermal treatment. The superhydrophobic surface based on nano-engineering still showed excellent anticorrosion performance, such as low corrosion current (∼10−10 A cm−2), large polarization resistance (>150.0 MΩ cm2) and low corrosion rate (∼10−6 mm/year). The good durability was attributed to the special nano-engineering with low surface roughness and surface energy. The work provides a new method to improve the durability of the superhydrophobic surfaces for application in anticorrosion technology.