Linear Polarization Curves Research Articles

Increasing of the corrosion resistance by preparing the trivalent nickel complex

This paper is intended to investigate the preparation of a complex ion Ni chloride (II) and with ligand Schiff base (N, N) dimethyl of the amino Benzaldhyde and characterized ligand prepared and complexion Ni chloride(II). These metallic organic chemical compounds have been checked using Spectroscopic Techniques Spectrums of infrared and spectra of UV. The study included a test of the Corrosion Rate of free matter and nickel complex in tap water solution in a linear polarization method By the linear polarization curves resulting from Tafel device readings. The results showed that the nickel complex has an effective inhibitory effect due to the low current value, which increases its corrosion resistance.

Corrosion Behaviour of Cu/Carbon Steel Gradient Material

Research on improving the corrosion resistance of carbon steel has become a hot topic in the iron and steel field in recent years. Copper plating on the surface of carbon steel is considered an effective means to improve its corrosion resistance, but the copper-plated carbon steel material prepared by this method has the problems of poor abrasion resistance, easy delamination of copper layer and similar issues, which affect the service performance of the copper-plated carbon steel material. To solve this problem, a new type of material whose surface is copper and the copper element is gradually diffused into carbon steel was developed by a plating-diffusion method, which is defined as a copper-carbon steel gradient material. Carbon steel with a copper plated surface and the Cu-Fe/carbon steel gradient material with 80% Cu content on the surface were prepared by the same method. The cross-sectional microstructure and composition of different samples were analysed, and the corrosion behaviors of samples in 3.5% NaCl solution were studied by the linear polarization curve method and electrochemical impedance spectroscopy. The cross-sectional microstructure result shows that the diffusion of copper in carbon is mainly carried out along its grain boundary, and the diffusion of copper will inhibit the growth of grains during heat treatment. As shown in the results of corrosion behaviors, there is no pitting corrosion in the corrosion process of all samples, as well as the stable passive film. All samples showed active dissolution. Compared with carbon steel, the corrosion potential of the Cu/carbon steel gradient material becomes more positive from −600 mV to −362 mV, the corrosion current density decreases from 53.0 μA/cm2 to 30.6 μA/cm2 and the radius of electrochemical impedance spectroscopy enlarges while the corrosion resistance is improved, and the corrosion resistance is mainly obtained by its surface copper layer. The corrosion resistance of Cu-Fe/carbon steel gradient material is lower than that of Cu/carbon steel gradient material, while it is still better than carbon steel, and it shows a clear passivation trend during corrosion. Therefore, the copper/carbon steel gradient material can significantly improve the corrosion resistance of carbon steel. Even after the surface copper layer is destroyed, the gradient material can protect the matrix and improve the service life of the material.

On the application of scattering matrix measurements to detection and identification of major types of airborne aerosol particles: Volcanic ash, desert dust and pollen

Atmospheric aerosols play key roles in climate and have important impacts on human activities and health. Hence, much effort is directed towards developing methods of improved detection and discrimination of different types of aerosols. Among these, light scattering-based detection of aerosol offers several advantages including applications in both in situ and remote sensing devices. In this work, new scattering matrix measurements for two samples of airborne desert dust collected in Spain and China are reported. The average extrapolated scattering matrices of airborne desert dust and of volcanic ash at two wavelengths have been calculated and compared with the aim of finding criteria to distinguish these two types of aerosol. Additionally, the scattering matrix of cypress pollen has been measured and extrapolated to explore differences with mineral dust that can be exploited in atmospheric detection. Field measurements of the backscattering linear depolarization ratio δL(180°) are used to obtain information about non-sphericity and discrimination between fine and coarse aerosol. However, the average δL(180°) for the three types of aerosols considered in this work in the visible spectral range is δL(180°) = 0.40 ± 0.05. This shows that δL(180°) is not informative about the composition or morphology of irregular particles. By contrast, measurements of scattering matrix elements or depolarization ratios at different scattering angles may provide information about the structural differences of particles, and in particular may enable to differentiate airborne volcanic ash from desert dust, which are otherwise similar in terms of size and optical constants. Cypress pollen shows a characteristic degree of linear polarization curve that is very different from that of polydisperse irregular mineral dust. Light scattering field instruments and remote sensing methods could extract more information about the characteristics of aerosol particles if modifications were introduced to measure the phase curves of several scattering matrix elements or depolarization ratios.

Investigation of Corrosion Protection of Austenitic Stainless Steel in 5.5 M Polluted Phosphoric Acid Using 5-Azidomethyl-7-morpholinomethyl-8-hydroxyquinoline as an Ecofriendly Inhibitor

The use of 5-azidomethyl-7-morpholinomethyl-8-hydroxyquinoline (AMH) as a corrosion inhibitor for AISI 321 stainless steel in 5.5 M polluted phosphoric acid was investigated using the hydrogen evolution technique, linear polarization curves, and impedance spectroscopy. Impedance measurements revealed that the dissolution of AISI 321 in 5.5 M polluted phosphoric acid was controlled by an activation mechanism, unchanged even with the addition of AMH at different concentrations. Polarization results showed that the inhibition ability was enhanced with increasing inhibitor concentration. AMH acted as a mixed-type inhibitor by random adsorption on the alloy surface, whatever the nature of the reaction that is taking place. The adsorption of AMH on the AISI 321 surface was also discussed via the Langmuir adsorption isotherm. The influence of elevating the solution temperature on the corrosion inhibition performance was studied. A quantum chemistry study with the DFT method was also conducted, which supplied a logical and exploitable theoretical explanation of the adsorption and the inhibition action of AMH on AISI 321.

Evolution of Electrochemical Behavior, Electrical Conductivity, and Microhardness of Electrodeposited W Coatings Enhanced by Ni During Long Immersion in 3% NaCl Media

This paper deals with detailed physical and electrochemical properties of electroplated W enhanced by massive Ni coatings. Corrosion behavior of elaborated deposits in 3% NaCl solution is examined, as well as the influence of immersion time in corrosive media on the morphology, electrical conductivity, and microhardness of all coatings. Characterizations are carried out using atomic force microscopy, scanning electronic microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. The linear polarization curve and EIS during long-term immersion tests were used to identify and quantify corrosion compounds on surfaces. All obtained coatings corrode in the 3% NaCl solution, leading to uniform corrosion for the enhanced W coating, while this is not the case for the pure Ni film. The main corrosion products for the enhanced W coatings are NiO, Ni(OH)2 and WO3.

Electrodeposition of Bi-Se thin films involving ethylene glycol based electrolytes

The work is devoted to the electrochemical deposition of Bi-Se thin films from ethylene glycol-based electrolytes. The studies have been carried out by potentiodynamic and galvanostatic methods under various conditions, using Pt and Ni electrodes. By recording cyclic and linear polarization curves, the potential range of deposition of thin Bi-Se films on Pt (-0.75 to -1.2 V) and Ni (0.2 to -0.85 V) electrodes was determined. A comparison of the polarization curves of two electrodes showed that co-electrodeposition of Bi and Se occurs in approximately the same potential range. In order to find the optimal mode and composition of the electrolyte, the effect of various factors (concentration of initial components, temperature, etc.) on the process of co-electrodeposition of Bi with Se was studied. In addition, the samples of Bi-Se thin films obtained on Ni electrodes using the galvanostatic method were studied by scanning electron microscope (SEM) and X-ray phase analysis. The results of X-ray phase analysis confirmed the formation of thin Bi2Se3 films with and without additional heat treatment step. Elemental analysis of obtained films carried out by EDS shows that films contained 62.79 wt. % Bi and 37.21 wt. % Se.

ELECTROCHEMICAL SYNTHESIS OF IRON MONOSELENIDE THIN FILMS

In the presented research work, the kinetics and mechanism of the deposition process of thin iron, selenium and Fe-Se films have been studied by recording a cyclic and linear polarization curves by potentiodynamic method using Pt and Ni electrodes. Individual and co-deposition potential areas of the components of the electrolyte on the Pt electrode were determined. In order to determine the optimal electrolysis mode and electrolyte composition, the effect of various factors (concentration of initial components, temperature, etc.) on the co-electrodeposition process of Fe-Se was studied. In addition, Fe-Se samples deposited on the surface of Ni electrodes were thermally treated at 4500C and studied by SEM and X-ray phase analysis methods. Elemental analysis of the films shows that they contain 42.2% Fe and 57.8% Se.

Alkyd based water-reducible anticorrosive paints and their antifungal potential

Concerns about ozone layer, contamination, fossils resources and health, has banned or restricted the use of traditionally organic solvents in paints. As a consequence, new resins that employed water as main solvent are being studied. Among these resins, alkyds are the most studied one as they can also be synthesised from natural vegetable sources, making them more acceptable.The aim of this paper was to study the anticorrosive behaviour of alkyd / polysaccharide paints containing zinc phosphate or zinc aluminum phosphate as main pigment and their performance against fungal growth. Two different PVC (pigment volume concentration) were studied. Painted panels were studied by exposition to salt spray and humidity chambers, where rusting and blistering degrees were evaluated, and by electrochemical tests (corrosion potential measurements, ionic resistances determination, linear polarization curves and polarization resistances determination).Results showed that these type of paints can be used to protect steel and that the type of pigment and the PVC are important to the protection. Besides, good selection of both also prevents fungi growth in a high humid environment.

Study of electrochemical deposition of Ni-Mo thin films from alkaline electrolytes

The process of co-deposition of Ni with Mo from alkaline electrolytes was studied by taking linear and cyclic polarization curves of Pt electrode at various concentrations of initial components and potential scan rates. Solutions of Na2MoO4∙2H2O and NiSO4∙7H2O were used as sources of ions of the main components in NH4OH electrolyte. It was found that co-deposition of nickel with molybdenum goes through the oxide formation stage, and a solid solution of these two metals is deposited on the cathode surface. The film obtained at constant current on Ni electrode under optimal conditions was found amorphous, but additional thermal treatment at 500 °C for one hour made it polycrystalline. This was confirmed by peaks in X-ray diffraction patterns, corresponding to NiMoO4, Ni, and MoO3. The proposed electrolyte and electrolysis conditions allow to obtain thin films with molybdenum content ranging from 17.1 to 50.9 at.%. The co-deposition of Ni with Mo is limited by diffusion of these ions to the cathode surface. The knowledge of the mechanism of co-deposition of Ni and Mo will make possible a selection of optimal conditions for deposition of alloys of the required composition with satisfactory electrocatalytic properties.

ELECTROCHEMICAL REDUCTION OF SELENIUM IONS FROM ORGANIC SOLUTION

Due to the unique properties of metal dichalcogenides, they are wide used in various fields of nano- and optoelectronics. Bi2Se3 is one of the promising n-type semiconductor materials belonging to the Av – Bvı group, with a band gap of 0.3 eV. To obtain these compounds by co-electrodeposition, we study the electroreduction of the initial components separately. Therefore, the study is devoted to the electrochemical reduction of selenite ions from the ethylene glycol solution. By drawing cyclic and linear polarization curves on Pt electrodes, the kinetics, the mechanism of the process, and the influence of various factors on the electroreduction of selenite ions are studied. Using the obtained data on the influence of temperature, the effective activation energy was calculated by the Gorbachov method. The calculation results show that the electroreduction of selenite ions from ethylene glycol is accompanied by electrochemical kinetics closer to diffusion

Nanocomposites formed by combination of urchin like NiS with Ni-nanoparticles/N-doped nanoporous carbon, derived from nickel organic framework, and decorated with RuO2 nanoparticles: Construction and kinetics for hydrogen evolution reaction

Fabrication of active, stable, and cost effective electrocatalysts, as alternative cathodes to Pt or Pt-based materials for catalytic hydrogen production, is important for different industrial purposes, such as hydrogen therapy in medicine, syntheses in pharmaceutical and nutrient, and clean carbon-free energy carrier in industry.Herein, construction, characterization and examination of an efficient electrocatalyst for hydrogen evolution reaction (HER) in alkaline media is reported. The catalyst system is based on nanocomposites formed of urchin-like nickel sulfide incorporated with nickel nanoparticles and nitrogen doped-nanoporous carbon, and decorated electrochemically with ruthenium (IV) oxide on the glassy carbon electrodes, leading to GCE-NiS/Ni/NNPC/RuO2 system.Physicochemical characteristics of the prepared composite systems are studied by several surface, solution and electrochemical methods, from which the system is characterized.Then, electrocatalytic activity of the GCE modified with the composite, is studied for the HER by means of the steady-state linear sweep voltammetry (LSV), polarization curves (Tafel plots), and electrochemical impedance spectroscopy (EIS). The obtained data are analyzed by using appropriate equivalent circuit models, from which the HER kinetics are quantitatively determined.The results revealed that the electrode modified with the prepared composite, GCE-NiS/Ni/NNPC/RuO2, is an efficient electrocatalyst for the HER in alkaline solution, where an overpotential of −82.54 mV at the current density of 20 mA cm‒2 (η20 =− 82.54 mV) with Tafel slope of 49.88 mV dec‒1 is observed. These activities are very close to those obtained on Pt-based electrode materials. The origin of the enhancement in the HER activity can be attributed to (i) the high surface area of the urchin-like structure along with nanoporous carbon, and (ii) the synergistic chemical coupling effects between the NiS, Ni/NNPC and RuO2nanoparticles.

Corrosion resistance of alkali-activated binary reinforced concrete based on natural volcanic pozzolan exposed to chlorides

Alkali-activated concretes are being considered as an alternative environmentally friendly construction materials compared to the ordinary Portland cement. However, although these materials have reported mechanical properties comparable to those of OPC, the corrosion of reinforcing bars is a major durability issue that needs to be studied. This article studies the corrosion performance of an alkali-activated binary reinforced concrete (AABC) based on natural volcanic pozzolan (NP) and ground blast furnace slag (GBFS) exposed to chlorides ions. OPC concrete was used as reference material. To carry out the study, accelerated chloride ingress methods (impressed voltage, wet-dry cycles, and saltwater immersion (3.5% NaCl)) were used. Monitoring of the corrosive process was carried out using the techniques of half-cell potential, linear polarization resistance, polarization curves and curves of current intensity versus time. As complementary techniques, surface electrical resistivity and resistance to chloride ion penetration were evaluated. AABC showed higher resistance to chloride ion penetration compared to OPC concrete, a reduction of the charge passed up to 60% at 360 days of exposition. In general, the various accelerated chloride ingress techniques employed in the present research revealed that reinforcing steel embedded in AABCs have a higher resistance to corrosion compared to steel bars embedded in Portland cement (OPC)-based concrete. It should be noted that the B constant values obtained for AABC differ from the values commonly used in (OPC)-based concretes. In addition, the results indicate that the ranges of corrosion probability, such as half-cell potentials or corrosion currents, specified for OPC concretes should be checked for its application in alkali-activated concretes.

Study of the anticorrosive properties of “quebracho colorado” extract and its use in a primer for aluminum1050

Tannins have been used to replace chromate in wash-primers as a temporary (“in transit”) protection for metals. In the present work, the anticorrosive properties of “quebracho colorado” tannins were tested in water solution and in wash primers to protect aluminum alloy 1050. Polarization curves (linear and Tafel) and corrosion potential measurements were done on the alloy in contact with different concentrations of the tannin. A tannin wash primer was prepared and coated panels were tested in 100% humidity chamber (ASTM D 2247) and by electrochemical techniques (linear polarization curves, corrosion potentials and ionic resistances). Chromate and talc primers as well as no-coated aluminum alloy were also tested, as control, to compare the results.

Near-infrared light photothermally induced shape memory and self-healing effects of epoxy resin coating with polyaniline nanofibers

Polyaniline (PANI) nanofibers were synthesized by interfacial polymerization at 20 °C. The ultraviolet–visible–near-infrared light (NIR) absorption spectra indicated two absorptions at 450 nm and 848 nm, which exhibited the NIR-absorbing characteristic of PANI. The photothermal conversion temperature of PANI nanofibers increased with the NIR power density of 808 nm. The nanofibers were added to the epoxy resin to prepare NIR-induced shape memory and self-healing coating. The shape memory effect of the composites was measured via NIR irradiation of 2 W cm−2 808 nm. The surface morphologies of the scratched and healed coatings were investigated by optical stereomicroscopy. The healing performance of the intact, damaged, and healed coatings was also evaluated by linear sweep voltammetry and polarization curves. Results indicated that the shape recovery time of the composite decreased as PANI content increased. The composite with 5 wt% PANI exhibited the best shape memory effect and multiple self-healing performances. Moreover, PANI nanofibers improved the protection performance of the epoxy resin coatings. The electrochemical results indicated that the coating with 5 wt% PANI had good self-healing performance when the scratched area was irradiated by NIR. This finding was attributed to the photothermal conversion effect and passivation function of the PANI nanofibers.

Experimental Phase Function and Degree of Linear Polarization Curves of Millimeter-sized Cosmic Dust Analogs

Abstract We present laboratory measurements of the phase functions and degree of linear polarization (DLP) curves of a selection of millimeter-sized cosmic dust analog particles. The set includes particles with similar sizes but diverse internal structure (compact and porous) and absorbing properties. The measured phase functions are found to be in all cases very different from those of micron-sized particles. They show a monotonic decrease with increasing phase angle from the back- to the side-scattering region, reaching a minimum at large phase angles before a steep increase of the forward peak. This is in stark contrast to the phase functions of micron-sized particles, which are rather flat at low and intermediate phase angles. The maximum of the DLP for millimeter-sized compact particles is shifted toward larger phase angles (∼130°) compared to that of micron-sized particles (∼90°). Porosity plays an important role in the measured DLP curves: the maximum significantly decreases for increasing porosity as a result of multiple scattering within the particle. Large porous particles with highly absorbing inclusions can reproduce both the OSIRIS/Rosetta phase functions and ground-based DLP observations of comet 67P/Churyumov–Gerasimenko.

Rebar corrosion behavior of coral aggregate seawater concrete by electrochemical techniques

Purpose Coral aggregate seawater concrete (CASC) is a new type of lightweight aggregate concrete that is becoming widely used in reef engineering. To investigate the corrosion behavior of different kinds of rebar in CASC exposed to simulated seawater for 0-270 d, the electrochemical techniques, including linear polarization resistance (LPR) technique and the electrochemical impedance spectroscopy (EIS), were used in the present work. Design/methodology/approach The electrochemical techniques, including LPR technique and the EIS, were used in the present work. Findings Based on the time-varying law of linear polarization curves, self-corrosion potential (Ecorr), polarization resistance (Rp), corrosion current density (Icorr), corrosion rate (i), and the characteristics of EIS diagrams for different types of rebar in CASC, it can be found that the anti-corrosion property of them can be ranked as epoxy resin coated steel > 2205 duplex stainless steel (2205S) > 316 L stainless steel (316 L) > organic coated steel > ordinary steel. Additionally, the linear regression equation between Rp and charge transfer resistance (Rct) was established. Finally, the EIS corrosion standard of rebar was established from the LPR corrosion standard, which provides a direct standard for the EIS technique to determine the condition of rebar in CASC. Originality/value The linear regression equation between polarization resistance and charge transfer resistance was established. And the EIS corrosion standard of rebar was established from the LPR corrosion standard, which provides a direct standard for the EIS technique to determine the condition of rebar in CASC.

From Half‐Cells to Membrane‐Electrode Assemblies: a Comparison of Oxygen Reduction Reaction Catalyst Performance Characteristics

AbstractSeveral studies relying on the improvements to the important oxygen reduction reaction (ORR) activity for increasing the performance of fuel cells have been reported. However, the application of catalyst conditions used for realizing the excellent activity in a half‐cell to a single‐cell does not guarantee the translation of the excellent performance. Therefore, we investigated the performance characteristics of various types of commercially available catalysts, including alloy catalysts, and compared the trends between the half‐cells and single‐cells using linear scan voltammetry (LSV), polarization curves (IVP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. Furthermore, regression analysis was performed to identify the influential factors for examining the complex relationship between the half‐cell and single‐cell performance parameters. The study reveals, that it is highly challenging to express the performances of the catalyst and single‐cell using isolated factors. Additionally, even though the measured activity of the catalyst in a half‐cell is higher than that in the other half‐cells, the difference does not manifest significantly in the single‐cell when the conditions required for its activity are not optimized, indicating that the overall performance of the fuel cell membrane electrode assembly (MEA) is not determined solely by the catalyst.

Short-period corrosion of X80 pipeline steel induced by AC current in acidic red soil

Effect of alternating current (AC) on the corrosion behavior of X80 pipeline steel has been investigated using electrochemical techniques and surface analysis methods in real acidic red soils. The AC current dramatically enhances the corrosion of steel coupon, and the corrosion rate increases with the AC current density increasing. Compared with strong polarization curve, linear polarization curve is more suitable to evaluate the AC corrosion tendency of the steel coupon. The oxidizing effect of the AC current which acts as an oxidant increases the contents of ferric ions, which verifies the Faradaic rectification effect.

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.

Experimental phase function and degree of linear polarization of cometary dust analogues

We present experimental phase function and degree of linear polarization curves for seven samples of cometary dust analogues namely: ground pieces of Allende, DaG521, FRO95002 and FRO99040 meteorites, Mg-rich olivine and pyroxene, and a sample of organic tholins. The experimental curves have been obtained at the IAA Cosmic Dust Laboratory at a wavelength of 520 nm covering a phase angle range from 3{\deg} to 175{\deg}. We also provide values of the backscattering enhancement (BCE) for our cometary analogue samples. The final goal of this work is to compare our experimental curves with observational data of comets and asteroids to better constrain the nature of cometary and asteroidal dust grains. All measured phase functions present the typical behavior for \mu m-sized cosmic dust grains. Direct comparison with data provided by the OSIRIS/Rosetta camera for comet 67P Churyumov-Gerasimenko reveals significant differences and supports the idea of a coma dominated by big chunks, larger than one micrometer. The polarization curves are qualitatively similar to ground-based observations of comets and asteroids. The position of the inversion polarization angle seems to be dependent on the composition of the grains.We find opposite dependence of the maximum of the polarization curve for grains sizes in the Rayleigh-resonance and geometric optics domains, respectively.