Linear Polarization Techniques Research Articles

In vitro corrosion behavior of Ti-Mo-W alloys in artificial saliva

Titanium and its alloys are preferred materials used for medical devices manufacturing due to their specific properties. The corrosion behavior in artificial saliva of the newly developed Ti-Mo-W alloys, with elastic modulus closer to the human bone value was studied by means of linear polarization technique in the following steps: i) measurement/monitoring of open circuit potential (EOC) over 6 hours; ii) tracing linear polarization curves from ±200 mV (vs. OCP) - Tafel plots, with a scan rate of 0.167 mV/s. Electrochemical tests were performed according to ASTM G59-97 (2014)using a Potentiostat/Galvanostatto which a low current interface (LCI) was coupled. The tests were performedin Fusayama Meyer artificial saliva with a pH of 5.2 at the human body temperature (37±0.5°C) which mimic the oral environment. The results indicate that the alloys Ti15Mo7W and Ti15Mo11W have better corrosion behavior than Ti6Al4V.

Magnetic field evolution in solar-type stars

AbstractWe discuss selected aspects regarding the magnetic field evolution of solar-type stars. Most of the stars with activity cycles are in the range where the normalized chromospheric Calcium emission increases linearly with the inverse Rossby number. For Rossby numbers below about a quarter of the solar value, the activity saturates and no cycles have been found. For Rossby numbers above the solar value, again no activity cycles have been found, but now the activity goes up again for a major fraction of the stars. Rapidly rotating stars show nonaxisymmetric large-scale magnetic fields, but there is disagreement between models and observations regarding the actual value of the Rossby number where this happens. We also discuss the prospects of detecting the sign of magnetic helicity using various linear polarization techniques both at the stellar surface using the parity-odd contribution to linear polarization and above the surface using Faraday rotation.

Evaluation of the electrocatalytic properties of Tungsten electrode towards hydrogen evolution reaction in acidic solutions

Hydrogen has concerned interest universally as an environmentally nontoxic and renewable fuel. Electrocatalytic hydrogen evolution reaction (HER) is one of the utmost favorable methods for hydrogen creation on a vast scale; however, the high cost of Pt-based supplies, which demonstrate the highest activity for HER, forced investigators to look for cheaper electro-catalysts. Tungsten has been considered as an effective, active and low cost electrocatalyst for the hydrogen evolution reaction, mostly in alkaline media, and we have investigated here its behavior in acid electrolytes. HER has been studied utilizing linear polarization technique and electrochemical impedance spectroscopy (EIS). It happens on W at rather low overpotential (−0.32 V vs. NHE at 10 mA cm−2, in 0.5 M H2SO4), yet more cathodic than the widely used Pt/C catalyst, but not so far from more sophisticated systems developed recently. The effect of acid concentration on the HER rate and the electrode stability was investigated. Cathodic transfer coefficient and exchange current density were calculated for the HER from Tafel curves obtained in H2SO4 solution at concentrations ranging from 0.1 to 3.0 M. EIS experiments were performed under both open circuit and/or cathodic polarization. It was found that the hydrogen evolution rate is relatively high under low overpotential, confirming that W is a possible applicant to substitute more expensive electrocatalysts usually used for the HER under acidic conditions. The process is economic and appropriate with no need for specific treatments, as supported by additional X-ray diffraction (XRD), Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) characterization of the tungsten electrode surface.

Corrosion Behavior of Fe-Al-Zn Interphased Dual Phase Steel in Marine Environment

Intercritical heat treatment operation has been in use for the development of Dual Phase Steel (DPS) and has been found to improve the mechanical properties of the steel. In spite of the enhancement a limitation was however observed as to its corrosion susceptibility. In a bid to further enhance the corrosion resistance of the DPS while maintaining its mechanical properties, galvanealing operation was adopted which involving the immersion of the DPS into Al-Zn melt and subsequently subjecting it to annealing operation at 550°C. Weight loss and linear polarization technique were used to measure or evaluate its resistance in 3.5% NaCl (a simulated marine environment). A minimum of 3 samples was used per immersion time. From the result, it was observed that there is a general sharp decrease in the corrosion rate of the GAS as compared to the control sample. The sample immersed and allowed to dwell in the melt for 20 seconds and further annealed with a soaking time of 20 minutes exhibited the highest corrosion resistance. The polarization curve also shows that the substrate was generally passivated, and this is as a result of the Al-Zn/Fe adhesiveness.

Integration of MoO2 Composite on the Micro-evolution and Anticorrosion Mitigation of Zn–Ni–MoO2 Thin Films Coating by Electrodeposition System

Zinc–nickel–molybdenum nano-composite coating was deposited on carbon steel substrate using electrolytic deposition technique. The MoO2 integration into zinc–nickel matrix was investigated with reverence to particulate concentrations from 10 to 15 g/L, voltage 5–1.0 V and 1 A/dm2. The effect of the percentage variation of MoO2 particle inclusion into the zinc–nickel lattices’ was seen, and surface morphology, with intermetallic phase transformation of the nano-composite were obtained using scanning electron microscopy coupled with energy dispersive spectroscopy. The corrosion behaviour and micro-hardness characteristics of the Zn–Ni–MoO2 composite deposits were studied using linear polarization technique. The result shows that the incorporation of MoO2 particles into the zinc–nickel matrix disperses evenly with increasing concentration of MoO2 particle and significantly modified the crystal orientation of the Zn–Ni–MoO2 deposit. A content of 10 g vol.% MoO2 particle incorporated Zn–Ni–MoO2 nano-composite deposit was found to obtained good corrosion, wear and better micro-hardness properties.

Corrosion behaviour of carbon steel and corrosion resistant steel under elevated temperature and chloride concentration in simulated concrete pore solution

Corrosion of reinforcing steel in marine environment is a major durability problem in reinforced concrete structures. This problem is exacerbated under hot weather conditions. Specialty steel bars are used in place of conventional carbon steel (CS) bars to avoid corrosion problems in severe environments. This article reports the corrosion-resistance behaviour of carbon and two specialty steel bars under varying chloride concentration (500, 1000 and 2000 mg/L) and temperature (25 and 55 °C). The corrosion resistance of CS and specialty bars was evaluated using linear polarization resistance and potentiodynamic polarization techniques. The morphology of the exposed specimens was evaluated using a scanning electron microscope coupled with energy dispersive spectroscope. The corrosion rate increased as the exposure temperature was increased from 25 to 55 °C. Uniform corrosion was noted on the specimens exposed to low temperature (25 °C) while pitting corrosion was noted on those exposed to elevated temperature (55 °C). Both uniform and pitting corrosion was noted, at both the exposure temperatures, on alloying/microstructure (A/M) steel while marginal pitting corrosion was noted on stainless steel (SS) specimens exposed to 55 °C. Polarization data indicated enhanced corrosion resistance of A/M and SS under hot chloride environments compared to CS bars.

Experimental and Computational Chemistry Studies on the Inhibition Efficiency of Phthalic Acid (PHA) for the Corrosion of Aluminum in Hydrochloric and Tetraoxosulphate (VI) Acids

In this work, phthalic acid is investigated for its corrosion inhibition properties (for aluminum in solutions of HCl and H2SO4) through experimental and computational chemistry methods. The experimental approach was achieved by using gravimetric (weight loss), linear and potentiodynamic polarization techniques as well as two spectroscopic techniques (Fourier transformed infra red and scanning electron microscopy). The theoretical approach incorporated the computation of semi empirical parameters and Fukui functions. Data obtained from weight loss were in strong agreement with those obtained from polarization methods. They generally pointed to the conclusion that phthalic acid inhibited the corrosion of aluminum better in solution of HCl than in solution of H2SO4. The inhibition efficiency of the inhibitor increases with increase in concentration but with increasing period of contact and temperature, the inhibition efficiency notably decreased. Confirmation of a physical adsorption mechanism was established by observed low values of activation energy and free energy of adsorption as well as the trend of decrease in inhibition efficiency with temperature. Frumkin and El awardy et al. adsorption isotherms best fitted the adsorption characteristics of phthalic acid on aluminium (in both HCl and H2SO4 media). The isotherms revealed that the inhibitor occupies more than one adsorption site and exhibited attractive behavior. Calculated quantum chemical parameters were within the range reported for good corrosion inhibitors while Fukui function, Huckel charge, HOMO–LUMO graphs and FTIR analyses indicated that phthalic acid is adsorbed on aluminum surface via the carboxylic oxygen atom.

Corrosion inhibition of N80 steel in simulated acidizing environment by N-(2-(2-pentadecyl-4,5-dihydro-1H-imidazol-1-YL) ethyl) palmitamide

A novel palmitic imidazoline compound, N-(2-(2-pentadecyl-4,5-dihydro-1H-imidazol-1-yl)ethyl)palmitamide (NIMP) has been successfully synthesized and characterized with Fourier transform spectroscopy (FTIR), Proton nuclear magnetic resonance (1H NMR), and Carbon-13 nuclear magnetic resonance (13C NMR). NIMP has been tested as corrosion inhibitor for N80 steel in 15% HCl solution at low and elevated temperatures using weight loss measurements, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), linear polarization (LPR), and electrochemical frequency modulation (EFM) techniques. The experimental investigation was supported with surface examination using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDAX), and Fourier transform spectroscopy (FTIR). NIMP is found to be effective in retarding N80 steel dissolution in 15% HCl solution at studied temperatures. The optimum concentration of NIMP is 300 ppm and this concentration afforded corrosion protection efficiency of 97.92% and 95.59% at 25 °C and 60 °C respectively from weight loss measurements. Chemisorption is proposed as the mechanism of adsorption of NIMP molecules onto N80 steel surface based on the value of standard enthalpy of adsorption (100.34 kJ/mol). PDP results disclosed that NIMP acted like a mixed type corrosion inhibitor but with principal effect on cathodic corrosion reactions. Surface screening results are in agreement with experimental results that NIMP molecules adsorbed on N80 steel surface. NIMP can be utilized as an acidizing corrosion inhibitor.

Enhancing Biocompatibility and Corrosion Resistance of Ti-6Al-4V Alloy by Surface Modification Route

Titanium (Ti) and its alloys are widely used as candidate materials for biomedical implants. Despite their good biocompatibility and corrosion resistance, these materials suffer from corrosion after implantation in biological environments. The aim of this research work is to study the effect of two coatings on biocompatibility and corrosion behavior of Ti-6Al-4V biomedical implant material. Hydroxyapatite (HA) and hydroxyapatite/titanium dioxide (HA/TiO2) coatings were thermal-sprayed on Ti-6Al-4V substrates. In the latter case, TiO2 was used as a bond coat between the substrate and HA top coat. The corrosion behavior of coated and un-coated samples in Ringer’s solution was studied by potentiodynamic and linear polarization techniques. Before and after corrosion testing, XRD and SEM/EDS techniques were used for the analysis of phases formed and to investigate microstructure/compositional changes in the coated specimens. The cellular response was analyzed by the MTT (microculture tetrazolium) assay. The results showed that both the HA, as well as, the HA/TiO2 coatings significantly increased the corrosion resistance of the substrate material. The HA coating was found to be more biocompatible as compared to the un-coated and HA/TiO2-coated Ti-6Al-4V alloy.

Economic use of waste Musa paradisica peels for effective control of mild steel loss in aggressive acid solutions

Cost effective prevention of steel corrosion utilizing eco-friendly materials is a high priority subject for the industries, these days. In this regard, we have explored ethyl acetate extract of Musa paradisica peels (EAEMPP) for mild steel protection in acidic media (hydrochloric and sulfuric acids). The electrostatic interaction of EAEMPP molecules with mild steel has been verified using UV–vis spectroscopy that clearly indicates extract molecules being adsorbed on the surface. The corrosion behavior of mild steel substrate in the presence of the fruit peel extract was investigated by Tafel polarization curves, linear polarization and electrochemical impedance spectroscopy (EIS) techniques. The results of electrochemical study strongly validate that EAEMPP limits the oxidation as well as reduction reactions at the active centers of the metal surface and thus retards mild steel corrosion in both acidic media. Variations in surface morphology of the mild steel with and without inhibitor have been studied via scanning electron microscopy (SEM) and atomic force microscopy (AFM), which has directly verified the reductions of corrosion loss. The adsorption behavior of the extract in both acid media is also studied, which is described suitably with Langmuir isotherm. Quantum chemical parameters, calculated by DFT calculations, have also aided in better understanding of the corrosion inhibition mechanism. We believe that employing green inhibitors from food waste may be useful in corrosion protection of mild steel with economical and ecological approach.

The vertical Non-uniform corrosion of Reinforced concrete exposed to the marine environments

Reinforced concrete (RC) structures usually are exposed to a wide variety of combined actions, which may cause various damages to the structures. The main objective of this study is to investigate the vertical non-uniform corrosion of reinforcement bar in concrete that was exposed to the marine environments. The concrete embedding rebar electrodes array (CRA) was designed and made based on the wire beam electrode (WBE). To simulate the submerged, tidal and splash marine environments, the marine environment simulation equipment (MESE) was set up. Electrochemical behaviors of rebar electrodes were characterized using the WBE method, linear polarization (LP) technique and electrochemical impedance spectroscopy (EIS). To monitor the carbonation and chloride ion penetration of concrete, the pH and chloride ion profiles of the concretes were analyzed. The vertical non-uniform corrosion of rebars was caused by the difference of oxygen concentration, moisture content, free chloride content and pH value in vertical direction. The macroscopic galvanic corrosion between the splash zone rebars and the tidal zone rebars was inhibited and the galvanic corrosion between the adjacent rebars was promoted by the high resistivity of the splash concrete. The concrete carbonation was a metathesis reaction between the bicarbonate ion (HCO3−) of seawater and the alkaline hydration products of concrete in the marine environments.

Gelatin: A green corrosion inhibitor for carbon steel in oil well acidizing environment

Corrosion inhibition performance of an environmentally benign compound, gelatin on X60 steel in 15% hydrochloric acid (HCl) at 25 °C, which simulate oil well acidizing environment was investigated in this study. The inhibition efficiency of the gelatin was examined using weight loss, potentiodynamic polarization (PDP), linear polarization (LPR), and electrochemical impedance spectroscopy (EIS) measurements techniques. Both the weight loss and the electrochemical results showed that the gelatin exhibits high inhibition efficiency and the inhibition efficiency increases with increasing gelatin concentration. The addition of low concentration of potassium iodide improves the inhibition efficiency of gelatin considerably. The ATR-FTIR and SEM/EDX surface morphology analyses provide evidence of formation of protective gelatin film on the metal surface. The gelatin molecules are predicted to adsorb on the metal surface through an interaction between the nitrogen and oxygen atoms of gelatin and the metal surface to form a metal/gelatin complex on the metal surface.

Electrochemical investigation of gel polymer electrolytes based on poly(methyl methacrylate) and dimethylacetamide for application in Li-ion batteries

In the present work, gel polymer electrolytes (GPEs) were prepared using poly(methyl methacrylate) (PMMA), lithium perchlorate (LiClO4) and dimethylacetamide as a plasticizer. Solution-casting technique was used to fabricate GPEs containing different weight percentage of PMMA. The degree of crystallinity of GPE samples was studied by X-ray diffraction (XRD) analysis. Fourier transform infrared (FT-IR) spectroscopy was applied to study the level of interactions between lithium salt and PMMA in the prepared GPEs. Electrochemical properties were studied by electrochemical impedance spectroscopy, linear sweep voltammetry and DC polarization techniques. Lithium ion conductivity of GPEs was determined by calculating the bulk resistance of polymer electrolytes from Nyquist plot. Increasing PMMA content of GPEs resulted in an improvement in the electrochemical potential window from 4.2 to 4.5 V. The highest lithium transference number (0.42) and also the best electrochemical properties were obtained for GPE containing 0.75 M LiClO4 and 10 wt% PMMA. Scanning electron microscopy images of the optimized GPE showed a porous and heterogeneous surface structure which is desirable for application in Li-ion batteries.

Effect of SnO2/SiO2 nano particle dispersant on the performance characteristic of complex multi-doped composite coating produced through electrodeposition on oil and gas storage tap

Abstract The effect of SnO2/SiO2 nano particle dispersant on the performance characteristic of complex zinc multi-doped composite coating produced through electrodeposition is studied. The degradation behaviour in term of wear and chemical corrosion activities were considered as a major factor in service. The wear mass loss was carried out with the help of reciprocating tester. The electrochemical corrosion characteristics were investigated using linear polarization technique in 3.5% simulated sodium chloride media. The outcome of the analysis shows that the developed coating was seen to provide a sound anti wear characteristics in its multidoped state. The corrosion resistance properties were observed to be massive compared to the binary based sample. It is expected that this characteristic will impact on the performance life span of storage tap in oil and gas.

Effect of current density and ZnO nano particles influence on the microstructure and mechanical strengthening properties of Zn-TiO<sub align="right">2-ZnO alloys at constant deposition time

In this work, the effect of current density and particle loading on microstructure and mechanical properties of Zn-TiO2-ZnO nanocomposite produced via electrocodeposition are investigated. The morphological characteristics of the nano-composite coatings were characterised by scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). Mechanical examination was carried out using Dura scan micro-hardness tester and CERT UMT-2 multi-functional tribological tester. The corrosion properties were evaluated using linear polarisation technique in 3.5% NaCl. The result showed that the coatings exhibited good stability and the quantitative particle loading significantly improved the micro-structural properties of the coating. It is also noticed that the hardness performance and corrosion resistance of the coatings were significantly impacted with over 70% improvement as against the as-received samples.

Effect of current density and ZnO nano particles influence on the microstructure and mechanical strengthening properties of Zn-TiO2-ZnO alloys at constant deposition time

In this work, the effect of current density and particle loading on microstructure and mechanical properties of Zn-TiO2-ZnO nanocomposite produced via electrocodeposition are investigated. The morphological characteristics of the nano-composite coatings were characterised by scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). Mechanical examination was carried out using Dura scan micro-hardness tester and CERT UMT-2 multi-functional tribological tester. The corrosion properties were evaluated using linear polarisation technique in 3.5% NaCl. The result showed that the coatings exhibited good stability and the quantitative particle loading significantly improved the micro-structural properties of the coating. It is also noticed that the hardness performance and corrosion resistance of the coatings were significantly impacted with over 70% improvement as against the as-received samples.

Recovery of Terbium from LiCl-KCl-TbCl3 System by Electrodeposition Using Different Electrodes

To extract terbium from LiCl-KCl-TbCl3 molten salts, the electrochemistry of Tb(III) was investigated on Cu and Zn coated W electrodes by a range of electrochemical techniques. A depolarization effect for Tb(III) reduction was observed on the two electrodes owing to the formation of Cu-Tb and Zn-Tb intermetallics. The Gibbs energies of formation for Zn12Tb and Cu5Tb were calculated by open circuit chronopotentiomery, and showed that the formation of Zn12Tb on Zn electrode is easier than the one of Cu5Tb on Cu electrode. The exchange current intensities for Tb(III)/Zn12Tb and Tb(III)/Cu5Tb couples were estimated using linear polarization technique. It was found that j0(Tb(III)/Zn12Tb) > j0(Tb(III)/Cu5Tb), which revealed that the reaction rate of Tb(III) on Zn electrode is faster than that on Cu electrode. The electroextraction of Tb was conducted on the two electrodes under the same conditions, and the extraction rates and efficiencies on liquid Zn electrode are higher than those on Cu electrode when electroextraction time is less than 3 h. The products were checked by XRD and SEM with EDS, and are comprised of Zn and Zn17Tb2 in the Zn-Tb alloy and CuTb and Cu2Tb in Cu-Tb alloy, respectively.

Effect of ionic liquid additives on oxygen evolution reaction and corrosion behavior of Pb-Ag anode in zinc electrowinning

Three ionic liquid salts, 1-Ethyl-3-methylimidazolium chloride [EMIM]Cl, 1-Ehyl-3-methylimidazolium bromide [EMIM]Br, and 1-Ehyl-3-methylimidazolium ethyl sulfate [EMIM]ESO4 were chosen as additives in order to examine their effects on the oxygen evolution reaction (OER) and corrosion of Pb-0.7%Ag anode in zinc electrowinning. Results of 24 h of anodic polarization showed that the presence of these additives depolarized the OER. A reduction of 25 mV of anodic potential was obtained by addition of 5 mg L−1 of [EMIM]ESO4 to that obtained from free-addition electrolyte. Corrosion measurements employing linear polarization technique revealed that corrosion rate of Pb-0.7%Ag was decreased by ∼25–42% by the addition of [EMIM]ESO4 or [EMIM]Br. Corrosion current was found to be decreased in the order of [EMIM]ESO4 < [EMIM]Br < Gelatin ≤ Blank < [EMIM]Cl. Electrochemical impedance spectroscopy demonstrated that addition of ILS to the zinc sulfate electrolyte increased the charge transfer resistance of the anodic dissolution reaction except for [EMIM]Cl. Zero resistance ammeter and scanning reference electrode techniques showed the same corrosion tendency obtained from other techniques and proved that no localized corrosion was observed in the presence of Cl¯ ions.

Performance Evaluation Effect of Nb2O5 Particulate on the Microstructural, Wear and Anti-corrosion Resistance of Zn–Nb2O5 Coatings on Mild Steel for Marine Application

In this study, we developed Zn–Nb2O5 composite coatings from sulfate bath for wear and corrosion performance on mild steel by electrodeposition technique. The effect of Nb2O5 particulate on the Zn–Nb2O5 properties was investigated. The particle volume fraction was varied within between 10 and 20 wt%. The structural properties of the composite coatings were characterized using scanning electron microscope equipped with energy-dispersive spectrometer. The hardness and wear of the composite coating were measured with diamond base microhardness indenter tester and sliding CETR reciprocating wear testers, respectively. The corrosion properties were examined in 3.65% NaCl using AUTOLAB 101 Metrohm potentiostat–galvanostat with linear polarization technique. The results showed that average hardness value of 192.6 and 200.6 HV and passivation potential of 4.39E?08 and 5.30E?08(X) were obtained for the 10–20 wt% Nb2O5 particulate on the Zn–Nb2O5 coatings. The wear performance improves by 63.4% as against the control sample. In all, this study established that up to 20 wt% of Nb2O5 in Zn–Nb2O5 composite coating significant corrosion, wear and microhardness propagation resistance of mild steel was attained.

Aspects of the Structure and Corrosion Resistance of Materials Used in Tongue Piercings

For centuries, piercing was an expression of art around the world and constituted a significant part of the culture and rituals of many different civilizations. This study evaluated the microstructure and the corrosion resistance in artificial saliva of two newly implantable devices used in tongue piercing. We investigated materials microstructure by optical microscopy and scanning electron microscopy (SEM), followed by an energy-dispersive X-ray spectroscopy (EDX) analysis in order to determine elemental composition. The corrosion resistance was determined by linear polarization technique. The corrosion tests were performed in artificial saliva Fusayama Meyer (composition: 0.4 gl-1NaCl, 0.9 gl-1 KCl, 1 gl-1 urea, 0.69 gl-1 NaH2PO4, 0.795 gl-1 CaCl * 2H2O) with a pH = 5.2 at temperature of 37 ± 0.5°C. The materials used for these types of implants were identified as Ti-6Al-4V alloy (sample 1) and austenitic stainless steel (sample 2). From corrosion resistance evaluation point of view, sample 1 showed the most electropositive value and hence better corrosion behavior compared to sample 2, having the Ecor potential -398.24 mV but this is clearly according the chemical composition of these two metallic biomaterials.