Linear Polarization Techniques Research Articles

Potential of Tomato Pomace Extract as a Multifunction Inhibitor Corrosion of Mild Steel

The aim of this paper is to investigate tomato pomace extract (TPE) as a multifunctional “green” vapor phase corrosion inhibitor for prevention from the atmospheric corrosion of mild steel and as a corrosion inhibitor in neutral media of 0.5 M NaCl solution. TPE would be an effective inhibitor with the efficiency of around 98% in both corrosive conditions. The chemical profile of the TPE was analyzed using gas chromatography mass spectrometry (GC–MS) and high-performance liquid chromatography analysis (HPLC-DAD-MS). The major volatile constituents identified in tomato pomace extract were alcohols (12.5%), fatty acids (23.78%), aldehydes (41.6%), ketones (8.65%), and terpenoids (9.11%). The predominant semi-volatile and high molecular weight chemical components in tomato pomace extract were phenolic acids and flavanols [caffeic acid (2.03 ± 0.3 μg/g), chlorogenic acid (37.23 ± 0.80 μg/g), gallic acid (10.2 ± 0.80 μg/g)]. The corrosion protection properties of the TPE as multifunctional corrosion inhibitor were studied using accelerated corrosion tests (weight loss method) and electrochemical methods [polarization curves and linear polarization technique (LPR)]. The mechanism of steel inhibition by TPE formulations was studied with the help of scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations. TPE acts as a "pro-inhibitor" of the steel corrosion in neutral solution. The analysis confirmed that the growth of inhibitory properties is prolonged and corrosion rate is reduced after 40–48 h of exposure. The inhibition efficiency increases with increasing exposure time and reaches 98% after 48 h. Quantum-chemical calculations were used to predict the adsorption/inhibition properties of some of the main compounds of the extract and compounds formed as a result of chemical conversion. This work to contributes interpretation/explanation and understanding of the mechanism of action of green corrosion inhibitors in neutral solution.

Corrosion Protection of CNTs/CNFs Modified Cement Mortars

The aim of this study is to examine the performance of nano additives in two different sets of mortar specimens armed with reinforcing steel rebars. In particular, three sets of reinforced concrete cylinders with additives of 0.1% wt of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been exposed to a solution of 3.5% NaCl, and further examined for the impact of nano-modification on corrosion performance. The anti-corrosive performance of these additives was investigated through linear polarization technique (LPR), mass loss and mercury porosimetry technique (MIP). From the investigation results, it is found that the addition of CNTs/CNFs causes lower steel corrosion, whereas the pore structure of concrete with CNTs/CNFs can significantly reduce the mass loss rate and the relative permeability.

Improving mild steel corrosion resistance in tap water: Influence of water flow and supply rates

The mild steel corrosion has been studied in hot tap water (50 °C) using linear polarization technique in the laboratory set-up that models water circulating system. The influence of water flow rate (0.15–0.45 m/s) and water supply rate (0–70 % of system volume per hour) on corrosion kinetics have been investigated. The corrosion products, formed on the surface of the steel corrosion probes, have been analyzed with XRD. It has been found, that in condition of low water flow rate (0.15 m/s) and in the absence of water supply the corrosion rate is high (0.29 mm/year) due to low blocking abilities of the surface deposits. Amorphous Fe(OH)3 is the main corrosion product to be detected on the surface. The increase in water flow rate above 0.15 m/s and water supply rate above 30 % of system volume per hour leads to the 1.6 times corrosion rate reduction (to 0.18 mm/year) due to the formation of dense surface layer of calcium carbonate and iron oxyhydroxides. The results obtained can be utilized to improve the corrosion performance of hot water supply systems.

Asidik Çözeltide Yumuşak Çelik için Çevresel Olarak Sürdürülebilir Yeni Bir Yeşil Korozyon İnhibitörü Olarak Plagiochila porelloides (Marchantiophyta)’e Genel Bir Bakış

In this study, the corrosion inhibition effect of Plagiochila porelloides (Torr. ex Nees) Lindenb. extract, a Marchantiophyta species, on mild steel in hydrochloric acid solution at 298 K was investigated for the first time by applying electrochemical impedance spectroscopy (EIS), linear polarization (LPR) and potentiodynamic polarization techniques. Experiments were performed by immersing mild steel electrodes in acidic solutions containing different concentrations of Plagiochila porelloides extract for 1 hour before each electrochemical measurement to equilibrate with the aggressive solution. Liverwort extract showed a strong inhibitory effect as a result of 1 hour electrochemical experiments, and as the extract concentration increased, the protective effect of mild steel in acidic solutions raised. In addition, the surface images of the electrodes in 1.0 M HCl solutions with and without liverwort extract after 1-hour exposure were examined by an optical microscope and it was shown that the metal surface in the inhibited extract solution had a smoother appearance compared to the uninhibited metal surface. Electrochemical findings and surface images support each other.

Electrochemical separation of La from LiCl-KCl fused salt by forming La-Pb alloys

To separate La from LiCl-KCl fused salt by forming La-Pb alloy, the electrochemical codeposition of Pb(II) and La(III) on inert W electrode and electroreduction of La(III) on liquid Pb were explored, respectively, using a group of electrochemical measurement methods. The formation mechanism reduction peak potentials of La-Pb intermetallics were obtained from the results of cycle voltammetry (CV), square wave voltammetry (SWV) and anodic stripping voltammetry (ASV). The kinetic data of La(III)/La (in Pb) couple on liquid Pb cathode, for instance, exchange current density, transfer coefficient, charge transfer resistance and activation energy, were studied by linear polarization and Tafel techniques. Moreover, constant potentials electrolysis (CPE) and constant current electrolysis (CCE) were conducted onliquid Pb cathode to recover La from fused salt. The electrolytic products checked by SEM-EDS and XRD were composed of LaPb3 phases.The maximum separation efficiency of La could reach 92.03% after CCE (0.15 A) for 7 h, which confirmed the feasibility of separating La from LiCl-KCl fused salt.

IMPROVING MILD STEEL CORROSION RESISTANCE IN TAP WATER: INFLUENCE OF WATER FLOW AND SUPPLY RATES

The mild steel corrosion has been studied in hot tap water (50 °C) using linear polarization technique in the laboratory set-up that models water circulating system. The influence of water flow rate (0.15-0.45 m/s) and water supply rate (0-70 % of system volume per hour) on corrosion kinetics have been investigated. The corrosion products, formed on the surface of the steel corrosion probes, have been analysed with X-Ray Diffraction (XRD). It has been found, that in condition of low water flow rate (0.15 m/s) and in the absence of water supply the corrosion rate is high (0.29 mm/year) due to low blocking abilities of the surface deposits. Amorphous Fe(OH)3 is the main corrosion product to be detected on the surface. The increase in water flow rate above 0.15 m/s and water supply rate above 30 % of system volume per hour leads to the 1.6 times corrosion rate reduction (to 0.18 mm/year) due to the formation of dense surface layer of calcium carbonate and iron oxyhydroxides. The results obtained can be utilized to improve the corrosion performance of hot water supply systems.

CARACTERIZAÇÃO E COMPARAÇÃO DE PROPRIEDADES MECÂNICAS E RESISTÊNCIA DE CORROSÃO DA TI-10MO-20NB, TI-6AL-4V E TI-CP PARA APLICAÇÕES BIOMÉDICAS

One of the main biomedical material for implants, the Ti-6Al-4V alloy, over time generates oxides of V and Al that accumulate in the body and cause cytotoxic effects. Researches have been making an effort for developing an alternative β metastable Ti alloy that combines corrosion resistance, biocompatibility and good mechanical properties. In view of this scenario, the present work aims to characterize a Ti-10Mo-20Nb alloy and compare the results obtained with a commercial purity Ti alloy and Ti-6Al-4V alloy. Ti-10Mo-20Nb samples were subjected to heat treatment at 1000°C, after that they were water quenched. A hot swagging process at 900°C was applied resulting on a cross section reduction of 80%. The alloy was characterized by optical microscopy, scanning electron microscopy (SEM), Vickers microhardness and the linear polarization technique. For the Ti-10Mo-20Nb alloy the ratio between the hardness and the elastic modulus was of 3.22, the hardness value of 238 HV and the elastic modulus of 74 GPa. The Ti-10Mo-20Nb alloy showed a better mechanical as well as biological compatibility due to the non-cytotoxic of its alloy elements, Mo and NB, in spite of the lower corrosion resistance value when compared to other alloys, it is still possessing reasonable resistance to corrosion and develops a remarkable passivation layer. As such Ti-10Mo-20Nb is a promising alternative for biomedical applications due to its superior mechanical properties and better biocompatibility with human bone.

Synthesis of Zinc Oxide Nanomaterials via Sol-Gel Process with Anti-Corrosive Effect for Cu, Al and Zn Metallic Substrates

Nanosized zinc oxide (ZnO) particles modified with different silane coupling agents (octyltriethoxysilane (OTES), octadecyltriethoxysilane (ODTES) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS)) were synthesized in basic catalysis using the sol-gel method. The structure and morphology were characterized by dynamic light scattering (DLS), environmental scanning electron microscopy (ESEM) and Fourier transform infrared spectroscopy (FTIR) for bonding characteristics. The final hybrid materials were deposited on three types of metallic substrates (aluminum (Al), copper (Cu) and zinc (Zn)) in order to obtain coatings with ultrahydrophobic and anti-corrosion properties. Water wettability was studied revealing a contact angle of 145° for the surface covered with ZnO material modified with ODTES. The water contact angle increased with the length of the alkyl chain supplied by the silica precursor. The anti-corrosive behavior of ZnO/silane coupling agents particles deposited on metallic substrates was studied by the linear polarization technique in neutral medium.

Double layer lanthanide –Pt/TiO2 nanotube arrays electrode as a cost-highly efficient electrocatalyst for hydrogen evolution in acid media

Self-organized anodic double layer TiO2 nanotube arrays (TNTAs) were sensitized by an electrochemical anodization process on a Ti sheet with a two-step anodization method. The prepared sample, followed by hydrothermal treatment with Nd(NO3)3 and/or Gd(NO3)3 and/or PtCl4 solution at 180 °C for 2 h, produced Nd-Pt-TNTAs, Gd-Pt-TNTAs, Nd-Gd-Pt-TNTAs and Pt-TNTAs. The morphological and structural properties were studied by SEM, XRD and Raman spectra techniques. The hydrogen evolution reaction (HER) performance on Lanthanides-Pt-TNTAs was investigated using the Tafel linear polarization technique. The calculated values of the activation energy are in good agreement with the trend in catalytic activity. The excellent performance of doped TNTAs with low activation energy (E a) is due to the formation of an excitation energy level below the conduction band of TiO2 from the binding of electrons with oxygen vacancies decreasing the excitation energy resulting in robust electrocatalytic activity. The very low value of E a for Nd-Gd-Pt-TNTAs (2.02 kJ/mol) compared to other electrochemical catalysts used for hydrogen evolution reactions containing titanium nanotubes was achieved for the first time. This makes the Lanthanides –Pt-TNTAs prepared in the present work optimal catalysts for electrodes and promising for applications in fuel cells or as water splitting materials. Highlights Synthesis of self-organized anodic double layer TiO2 nanotube arrays (TNTAs) on a Ti sheet with a two-step anodization method. Nd, Gd, Pt were deposited on anodic TNTAs arrays by hydrothermal method. The HER mechanisms on Lanthanides-Pt-TNTAs in acidic media has been discussed. The order of catalytic activity based on the values of activation energy was Nd-Gd-Pt-TNTAs > Gd-Pt-TNTAs > Nd-Pt-TNTAs > Pt-TNTAs > undoped TNTAs.

Electrodeposition and Growth of Iron from an Ethylene Glycol Solution

The electrochemical reduction of iron (III) ions into zero-valent iron from a solution of ethylene glycol was accomplished. The kinetics and mechanism of the electroreduction process were investigated by cyclic and linear polarization techniques. The influence of temperature, potential sweep rate, and concentration of iron (III) ions on the electroreduction process was also studied. The observed values of effective activation energy revealed that the investigated electroreduction process is accompanied by mixed kinetics control. Moreover, the results of SEM and X-ray diffraction analysis confirmed the deposition of thin Fe films under the optimized conditions.

Development of novel electrochemical sensor for the detection of biological warfare agents: enzyme, antibody, and DNA free

There is an urgent need to develop a novel sensor that can quickly and accurately detect biological warfare agents (BWAs). A novel electrochemical sensor was specially designed and developed for Staphylococcus aureus as a potential BWAs without using any enzyme, antibody, or genetic material. Cyclic voltammetry (CV), linear resistance polarization (LRP), chronoamperometry, impedance spectroscopy, and Differential Pulse Voltammetry (DPV) techniques were used for fast and accurate detection of BWAs. Co-precipitation technique was used for the synthesis of CuO nanoparticles (NPs) for their use in the electrochemical sensor. The effect of temperature, stirring and addition of CuO NPs was thoroughly investigated. The storage, stability, and performance of electrochemical sensor was tested for 45 days. The current response of the electrochemical sensor was found linear with the correlation coefficient, R2 = 0.991. The major advantage of this novel electrochemical sensor is that immobilization of enzyme, antibody, or DNA is not required in sensing technology as the immobilization process makes biosensors a highly specific. The novel electrochemical sensor was very quick, accurate, non-specific, and provide reliable results in the qualitative and quantitative estimation of pathogenic bacteria as a potential BWAs. A novel electrochemical sensor was specially designed and developed for the detection of Staphylococcus aureus pathogenic bacteria as a potential BWAs without using any enzyme, antibody, or genetic material. Cyclic voltammetry, linear resistance polarization, chronoamperometry, impedance spectroscopy, and Differential Pulse Voltammetry (DPV) experiments were carried out for fast and accurate detection of BWAs. Storage, stability, and reusability of the electrochemical sensor was tested for continuous 45 days. The current response of the electrochemical sensor was found to be linear with the correlation coefficient, R2 = 0.991. The major advantage of this novel sensor is that immobilization of enzyme, antibody, or DNA is not required in sensing technology as the immobilization process makes biosensor a highly specific. The novel electrochemical sensor was proved to be very quick, accurate, non-specific, and provide reliable results in the qualitative and quantitative estimation of pathogenic bacteria as a potential BWAs.

The Effect of Nb2O5-Ni Coatings on the Microstructural and Corrosion Behavior on Carbon Steel for Marine Application

In this study, we developed Nb2O5-Ni composite coatings on carbon steel by DC sputtering technique. The effect of Nb2O5 particulate on the Ni coating properties was investigated. The weight percents of Nb2O5 in Ni coating were 0, 12, 15, and 30 wt%. The structural properties of the composite coatings were characterized using scanning electron microscope equipped with energy-dispersive spectrometer. The microhardness and thickness of composite coatings were measured, in addition to examine the corrosion properties in 3.5% NaCl using MLab 200 potentiostat/galvanostat with linear polarization technique. The results showed that hardness value increased to 164 HV for 30 wt% Niobia compared with 155 HV for Ni coating and the thickness increased slightly for Nb2O5-Ni composite coatings. The corrosion performance improved to obtain efficiencies better than Ni coating alone.

Surface effect of environmentally assisted corrosion growth of automotive welded steel performance

Failure of steel in automobile industries due to environmentally assisted medium in service is alarming. In this study an effort has been made to investigate critically the corrosion induced performances of automotive welded part. The experimental correlation on the effect of corrosive media (NaCl and HCl solutions) on the base metal, heat affected zone (HAZ) and weld metal formed were examined using linear potentiodynamic polarization technique. The hardness, microstructural and phase rationale of the studied joint was evaluated using, diamond base indenter, Scanning electron microscope and x-ray diffractograms respectively. The results revealed that the base metal has no detrimental phase transformation unlike the HAZ and the weld joint region. The hardness value of 185 HV welded joint was obtained compared to 235.95 HV of base region. The corrosion propagation in the 3.5NaCl and 1 M HCl shows that pitting deterioration occurs at the welded position in all case as a result of the shift in grain refinement and micro-straining during welding process.

Petiveria alliacea root extract as Green Inhibitor for Acid Corrosion of Aluminium

Corrosion inhibition of aluminium in 0.5M 𝐻 􀀀􀀁􀀂 by methanol root extracts of Petiveria alliacea was investigated by weight loss and linear polarization techniques. The weight loss is concentration dependent and increases with increasing concentration of Petiveria alliacea root extracts (PARE). The inhibitor (PARE) exhibited highest inhibition efficiency of 75.28% at the highest inhibitor concentration of 8g investigated. Inhibition was found to increase with increasing PARE concentration. PARE showed molecular adsorption of phytochemicals present as active ingredients through the hetero atoms in their molecules. Polarization studies showed that the extracts act as a mixed type inhibitor. The inhibitor obeyed the Langmuir adsorption isotherm equation.

Electrochemical extraction of metallic Y using solid and liquid double cathodes

To select proper electrode material for the extraction of rare earth elements and purification of salt, double cathode electrolysis cell was designed to compare the extraction of Y on solid and liquid electrodes. The electrode process kinetic and thermodynamic data of Y(III) on liquid Zn electrode and solid Cu electrode were studied employing cyclic voltammetry (CV), open-circuit chronopotentiometry (OCP) and linear polarization (LP), respectively. The thermodynamic results indicated that the reduction peak potentials of (Y–Zn)solution and Zn-rich Y–Zn compound are more positive than that of Cu-richest Y–Cu compound, and the standard molar Gibbs energy of formation for (Y–Zn)solution is smaller than those for Y–Cu compounds, which meant (Y–Zn)solution formed easily. Furthermore, the dynamic properties, such as exchange current densities and charge-transfer resistances of Y(III)/Cu7Y and Y(III)/(Y–Zn)solution couples, were determined employing LP technique. The reaction activation energies for the two couples were also estimated according to the relationship of exchange current density and temperature, which showed the reaction activation energy for Y(III)/Cu7Y couple is larger than that for Y(III)/(Y–Zn)solution couple. To compare to the extraction rate and efficiency, the electrochemical extracting Y on single cathode (solid Cu or liquid Zn) and double cathodes (solid Cu and liquid Zn) was executed by constant current electrolysis under same conditions. The results displayed that the extraction rate and efficiency of metallic Y is higher on liquid Zn electrode in the first 6 h, and only a small amount of metallic Y was deposited on solid Cu electrode in double cathode system.

Anodic Protection Assessment Using Alumina-Forming Alloys in Chloride Molten Salt for CSP Plants

The generation of a natural protective coating in alumina-forming alloys was analyzed using a ternary chloride molten salt as a thermal energy storage material for concentrated solar power (CSP) technology. The formation of the protective layer was monitored using electrochemical impedance spectroscopy (EIS). A protective layer model for the OCT alloy and a localized corrosion model for the OCI and OC4 alloys were obtained after 5 h of immersion. The corrosion rates calculated using the linear polarization technique (LPR), were 8.03, 21.55, and 7.61 mm/year for OC4, OCI, and OCT alloys, respectively. These results were confirmed by scanning electron microscopy and X-ray diffraction. Our analysis showed that MgAl2O4 was the main protective coating generated by the alumina-forming alloys.

Electrochemical Reaction of Sm(III) on Liquid Sn Electrode

The electrochemical study of Sm(III) ions was conducted on Sn film electrode in eutectic LiCl-KCl in the temperature range from 773 K to 923 K by a series of electrochemical techniques. The results of current reversal chronopotentiometry of Sm(III) on W electrode showed that the redox reaction related to Sm(III) is a kind of soluble/soluble system, which meant that Sm(III) was reduced to Sm(II) on W electrode. On Sn film electrode, the reduction of Sm(III) was found to be two-step process: Linear polarization (LP) and Tafel techniques were conducted to measure the exchange current density (j0) of Sm(II)/SmSn3 couple. The variation of j0 with temperature accords with the Arrhenius law, and the activation energy was evaluated to be 14.32 kJ mol−1 and 14.08 kJ mol−1, respectively. Moreover, the feasibility of extracting Sm on Sn film electrode was examined by constant potential electrolysis at −1.45 V in the LiCl-KCl-SmCl3-SnCl2 molten salt for 3 h. XRD result indicated the formation of SmSn3. Constant current and potential electrolysis were performed to extract metallic Sm on liquid Sn pool electrode. The alloy samples were characterized by SEM-EDS and XRD, which displayed the existence of SmSn3 and Sm4Sn3 phases in Sm-Sn alloys.

Improving the structural properties and corrosion behaviour of electroless deposited Ni-P-Zn coatings on mild steel for advanced processes

Hydrated crystal of ZnSO4·7H2O was co-deposited with NiSO4·6H2O, and NaH2PO2·H2O processed electrolyte to develop a ternary phase electroless coating on mild steel for advanced application. The coating was produced in an aqueous nickel electrolyte solution with zinc at a temperature of 90 ℃ and varying time conditions between 20 and 50 min. The effects of the developed coatings on microstructure and physical properties were investigated using scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), and optical microscopy. The corrosion characteristics of the coatings examined in 0.5 M H2SO4 and 3.5% NaCl were analyzed using linear potentiodynamic polarization technique. The microstructure revealed that the constituent deposited on the steel. A more uniformly distributed crystallite with minimal pores was observed at 20 min of Ni-P-Zn coating, while the tiniest film was observed at 50 min of the coating without crack. There was also a fully compact grain within the intermetallic matrix of the coating due to the synergetic effect of the electrolyte constituent with the strengthening phase of Zn7Ni4P2, Zn2Ni5P, and Zn3Ni. Corrosion study established that Ni-P-Zn exhibits significant corrosion resistance at the optimum time within the examined environments with little SO42- and Cl- ions.

Nickel-nanodiamond coatings electrodeposited from tartrate electrolyte at ambient temperature

In this study, nanocrystalline Ni and Ni-diamond coatings were obtained by electrodeposition from tartrate electrolyte at ambient temperature aiming at improving corrosion and wear properties of the material. The created surfaces were investigated with regard to microhardness, adhesion, wear- and corrosion-resistance. The various methods such as atomic force microscopy, scanning electron microscopy, electrochemical impedance spectroscopy and linear polarization technique were applied to study the coating surface properties. The introduction of nanodiamond particles into the coating led to a rougher surface structure and a bigger grain size in comparison to bare nickel coating. Our study shows that the addition of 5·10−2 (g dm−3) of nanodiamonds to the plating bath is enough to obtain composite coatings with a clear increase in microhardness and wear resistance. The slightly improved corrosion resistance of the coating, decrease in corrosion current density from 0.41 to 0.14 μA cm−2 in neutral chloride-containing medium, and nobler values of the corrosion potential were also observed.

Mechanical and corrosion behaviour of hydroxyapatite reinforced Mg-Sn alloy composite by squeeze casting for biomedical applications

Abstract Magnesium alloys have gained increasing attention for biomedical applications due to their biocompatibility and the biodegradability. Hydroxyapatite (HA) is known to be a highly bioactive because of its similar chemical and crystallographic structures to bone. Therefore, HA is believed to be a potential ceramic material for the fabrication of Mg based composites, to combine the advantages of both Mg and HA. But, in general, the composites known to be more susceptible to corrosion attack than the matrix alloy. Hence, in the present work, Sn is used as an alloying element to evaluate its effect on mechanical as well as corrosion properties of Mg/HA composites. Mg with 5 wt% HA and Mg-1 wt% Sn-5 wt% HA composites were prepared separately by stir assisted squeeze casting route. The phase analysis and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS) respectively. Mechanical properties were evaluated by conducting the compression and micro hardness tests. Corrosion properties of as-cast composites were studied by linear polarization, Tafel and electrochemical impedance spectroscopy (EIS) techniques. The results of both XRD and SEM-EDS revealed that the main constitutional phases of as-cast Mg/HA composites were α-Mg and HA whereas, in Mg-Sn/HA composites, the phase Mg2Sn was observed along with fine distribution of HA particles. In both the cases, no interfacial reactions observed. The yield strength, ultimate compression strength and hardness were found to be increased with the addition of Sn in Mg/HA composites. Furthermore, the addition of Sn also played an important role in increasing the corrosion resistance of the Mg/HA composites which was attributed the refinement of grain size and the formation of Mg2Sn phase along the grain boundaries. Hence, it was concluded that the addition of Sn improves both mechanical and corrosion properties of Mg/HA composites.