Polarization Curve Method Research Articles

Adsorption properties and inhibition of mild steel corrosion in hydrochloric solution by some newly synthesized diamine derivatives: Experimental and theoretical investigations

New diamine derivatives, namely 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]ethanol (DAME) and 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]propanol (DAMP) were synthesised and their inhibitive action against the corrosion of mild steel in 1 M HCl solution were investigated at 308 K. The detailed study of DAME is given using gravimetric measurements and polarization curves method. Results show that DAME is a good inhibitor and inhibition efficiency reaches 91.7% at 10 −3 M. Tafel polarization study revealed that DAME acts as a mixed-type inhibitor. The inhibitor adsorption process in mild steel/DAME/hydrochloric acid system was studied at different temperatures (308–353 K) by means of weight loss measurements. The adsorption of DAME on steel surface obeyed Langmuir’s adsorption isotherm. The kinetic and thermodynamic parameters for mild steel corrosion and inhibitor adsorption, respectively, were determined and discussed. The comparative study of inhibitive performance of the two diamine derivatives revealed that DAME is more effective than DAMP. Quantitative Structure–Activity Relationship (QSAR) approach has been conducted in attempt to correlate the corrosion inhibition properties of these diamine derivatives with their calculated quantum chemical parameters.

Interaction of Ti–6 wt.% Si alloy with tissue fluid: experimental modeling

The methods of potentiodynamic polarization curves and quantitative Auger electron spectroscopy are used to determine the mechanism whereby a dense protective nanofilm (up to 20 nm thick) forms. The film consists of Ti2O, TiO, and Ti2O3 lower titanium oxides and forms under the layer of TiO2 (10 nm) and oxygen chemisorbed over an orthopedic prosthesis (90.2 at.% Ti–9.8 at.% Si alloy) during electrolysis in a 3% NaCl solution, as the main component of the tissue fluid (Hank’s physiological solution).

ANODIC ELECTROCHEMICAL BEHAVIOR OF X80 PIPELINE STEEL IN NaHCO<SUB>3</SUB> SOLUTION

X80 steel has the potential to be widely used for building the gas transmission pipelines because of its high-intensity and high-toughness. Its corrosion performance is a key problem for the life expectancy, especially in soil environment. The anodic electrochemical behavior of X80 pipeline steel in NaHCO3 solution was studied using potentiodynamic polarization curve, dynamic electrochemical impedance spectroscopy (DEIS) as well as SEM observation. The results show that the shape of the polarization curves changes with HCO 3 concentration. The corrosion rate of X80 pipeline steel first increases and then decreases with the increase of HCO 3 concentration. 0.009 mol/L is the critical concentration of HCO 3 for forming the passive film of the X80 pipeline steel. There is no anodic current peak in the solution when HCO 3 concentration is below 0.009 mol/L, and one anodic current peak below 0.05 mol/L and two anodic current peaks above 0.1 mol/L. The results of the DEIS measurements are in complete agreement with the potentiodynamic polarization curve. The corrosion products change with polarization potential and two equivalent circuits are used to explain the experimental spectra of X80 pipeline steel in the whole corrosion process. Therefore, the combination of dynamic polarization curve and DEIS methods can be well used to investigate the corrosion behavior of X80 pipeline steel in NaHCO3 solution at various potentials. In addition, different corrosion products forming at various potentials and the corrosion mechanisms of X80 pipeline steel are briefly analyzed.

Совместное электролитическое осаждение оксида кобальта (III) с оксидами никеля (III) и хрома (III) и образование бинарных оксидных систем

With the help of the polarization curves method (E-lgIa) there are investigated the anode processes at Co2O3 anode deposition together with the doping additives – nickel (NiO, Ni2O3) and chromium (Cr2O3) oxides at the electrolysis from the mixed sulfate solutions. The possible mechanisms of these processes interconnection with nucleation and crystal growth of binary oxide compounds of Co-Ni and Co-Cr and crystal structure formation of anode deposits are considered.

Protective oxide layers formed during electrochemical oxidation of hafnium carbide

The composition of oxide nanofilm formed on the HfC anode under electrolysis of a 3% NaCl solution at potentials between – 0.20 and +1.90 V is studied using the potentiodynamic method of polarization curves and Auger electron spectroscopy and SEM methods. The film consists of the upper layer formed in polymolecular chemosorption of O2 and Cl2 gases followed by the HfO2 + C (1 : 1) layer. Two inner layers represent a 7 at.% O2 solid solution in HfC and a mixture of HfC0.7O0.3 and HfO (7 : 1). The oxide film 30–40 nm thick formed at potentials up to 1.35 V is protective and ensures very high corrosion resistance of HfC without any further polarization.

Microencapsulation technology for thiourea corrosion inhibitor

The microencapsulation technology was brought in to solidify corrosion inhibitor in order to prolong the releasing time of it. In this work, thiourea (H2NCSNH2) was used as a corrosion inhibitor and microcapsuled using glutin and polyvinyl alcohol (PVA), respectively, as protective agent. The re-sealing process was used as a way to prolong the releasing time of the H2NCSNH2 encapsulated in microcapsules. It was found that the H2NCSNH2 microcapsule corrosion inhibitor using PVA as a protective agent had a better releasing time. The releasing times of the H2NCSNH2 microcapsule corrosion inhibitors were prolonged from 18 to 48 h by re-sealing process and using PVA as a protective agent. Both the use of PVA as a protective agent and the application of the re-sealing process decreased the encapsulation efficiency of the H2NCSNH2. The performance parameters on protecting Q235 carbon steel from corrosion in 0.1-M H2SO4 solution were evaluated by polarization curve and electrochemical impedance spectra methods. The results showed that the H2NCSNH2 released into the solution from microcapsules could well protect Q235 carbon steel from corrosion and the corrosion-inhibiting mechanisms of it were the same as that of H2NCSNH2.

Influence of embedded particles on microstructure, corrosion resistance and thermal conductivity of CuO/SiO 2 and NiO/SiO 2 nanocomposite coatings

Homogeneous CuO/SiO 2 and NiO/SiO 2 nanocomposite coatings containing CuO and NiO nanoparticles in silica matrix were successfully synthesized by sol–gel process on an aluminum alloy substrate, respectively. The evolution of phase and morphology of both nanocomposites was characterized by XRD, SEM, TEM and FTIR. The effect of incorporating various nanoparticles on the corrosion behavior and the thermal conductivity of nanocomposite coatings was investigated by potentiodynamic polarization curve and comparative exponential method. The thermal conductivity as well as the corrosion resistance of nanocomposite coatings was significantly improved by the introduction of metal oxide particles. In comparison with NiO/SiO 2 nanocomposite coatings, CuO/SiO 2 composite coatings displayed lower protective behavior as well as higher thermal conductivity. Experimental results revealed that those improvements can directly be related to the nanocomposite effect and the nature of added nanoparticles.

Effect of 3-Amino-5-mercapto-1,2,4-triazole on Electroless Nickel Deposition

Abstract The effects of organic additive, 3-amino-5-mercapto-1,2,4-triazole (AMTA) on bath stability, deposition rate, reaction activation energy, and Ni-P coating composition in acidic electroless nickel plating were investigated. Polarization curve method and infrared reflection spectroscopy were used to analyze the mechanism of the effect of AMTA on electroless nickel deposition. It was observed that AMTA improved bath stability, decreased the deposition rate, and increased the reaction activation energy. It was also revealed that AMTA decreased the phosphorus content and increased the sulfur content in Ni-P coating. In addition, AMTA inhibited the anodic oxidation of hypophosphite and accelerated the cathodic reduction of Ni2+. Infrared reflection spectroscopy result indicates that AMTA was adsorbed on the surface of Ni-P and interacted with Ni2+ to form an AMTA-Ni2+ compound. On the basis of the results of this study, the mechanism of the effect of AMTA on electroless nickel deposition was deduced.

Anodic processes occurring upon V2O5 electrodeposition

Kinetics of the anodic processes occurring upon V2O5 electrodeposition from VOSO4 solutions containing Na+ ions was studied by the method of polarization curves. The mechanism of their formation was suggested, based on the analysis of the morphology of the deposit surface.

Hydrogen peroxide reduction on amalgamated platinum electrodes covered with a monolayer of stearic acid

The reduction of hydrogen peroxide and, for comparison, oxygen on an amalgamated platinum electrode covered with a monolayer of stearic acid is studied by methods of polarization curves and impedance spectroscopy. In contrast with the oxygen reduction, the reduction of dissolved hydrogen peroxide occurs predominantly on the monolayer surface, rather than inside it. This is explained by the difficulty of penetration of the polar molecule of hydrogen peroxide into hydrocarbon environment.

Metal Removal Rate of the Electrochemical Mechanical Polishing Technology for Stainless Steel - The Electrochemical Characteristics

Electrochemical mechanical polishing technology was studied in this research in order to investigate the effects of electrochemical parameters such as the electrolyte, pH values, and operating potential on the metal removal rate of polishing AISI 316L stainless steel (SS316L). The dynamic polarization curve method was employed to evaluate the effects of the compositions of electrolyte (phosphoric acid and H2O2) and electrochemical parameters (pH values, H2O2 concentration, and operating potential) on the metal removal rate of SS316L. The results showed that SS316L, in the lower-pH-value electrolyte solution, will have a shorter passive region and higher current densities of both passive and trans-passive regions. The concentration of hydrogen ions was higher at lower pH values, resulting in damage of the passive film. The H2O2 additive will also release hydrogen ions which will accelerate the reaction. Thus, the passive region was severely shortened. However, the H2O2 will also release OH− ions. Therefore, the pH value of the electrolyte will increase slightly, and the current density in the trans-passive region decrease slightly. The electrochemical reactions were strong (higher metallic dissolution rate) at pH 2 solution. Therefore, the metal removal rate was higher. An appropriate amount of H2O2 additive (6 vol %) may also improve the electrochemical reactions and increase the polishing efficiency.

Continuous electricity production from artificial wastewater using a mediator-less microbial fuel cell

A microbial fuel cell (MFC) was optimized in terms of MFC design factors and operational parameters for continuous electricity production using artificial wastewater (AW). The performance of MFC was analyzed through the polarization curve method under different conditions using a mediator-less MFC. The highest power density of 0.56 W/m 2 was achieved with AW of 300 mg/l fed at the rate of 0.53 ml/min at 35 °C. The power per unit cell working volume was 102 mW/l, which was over 60 times higher than those reported in the previous mediator-less MFCs which did not use a cathode or an anode mediator. The power could be stably generated over 2 years.

Kinetics and mechanism of electrolytic corrosion of titanium-based ceramics in 3% NaCl solution

The kinetics of electrolytic oxidation (in 3% NaCl solution at 20 °C) of TiN–AlN, TiB 2–AlN, TiB 2–TiN and TiC 0.5N 0.5 binary ceramics, manufactured by HIP method, were studied using a potential-dynamic method of polarization curves. For determination of oxidation mechanism, the chemical analysis concerning titanium ions state in the solution as well as an XRD, SEM and AES analyses of oxidized surface layers were used. In all the cases the oxidation of ceramics above proved to be the multistage process, the peculiarities of different stages were discussed on the base of experimental data obtained by the methods pointed out. It was shown that these ceramics are exceptionally corrosion-resistant. The rate of oxidation only slightly increases in the row: TiN–AlN → TiB 2–AlN → TiB 2–TiN → TiC 0.5N 0.5.

Electrochemical Properties of Intermetallic Compounds Mg2Ni, MgNi2, and the Hydride Mg2NiH4in 30% KOH Solution

Using the potentiodynamic polarization curve method, x-ray phase analysis, and Auger electron spectroscopy, we have studied the mechanisms for cathodic and anodic processes occurring in a 30% KOH solution on the surface of the intermetallic compounds Mg2Ni, MgNi2 and the hydride Mg2NiH4. In contrast to MgNi2, we observed hysteresis of the cathodic polarization curve for Mg2Ni due to formation of a surface layer (a mixture of the hydride phases β‐Mg2NiH4 and Mg2NiH3.85) on the sample, as a result of reaction between Mg2Ni and atomic hydrogen. We have shown that the surface of the samples is considerably enriched in magnesium and depleted of nickel, and their corrosion resistance in the indicated electrolyte is determined by active dissolution of nickel and formation of a surface layer (∼25 nm) on the electrodes consisting of MgO and Mg(OH)2 in the case of Mg2Ni and Mg2NiH4, and also of MgO, Mg(OH)2, and NiO in the case of MgNi2. The intermetallic compound MgNi2 was the most corrosion-resistant, probably because of the presence of a monolayer of the oxides MgO and NiO on the original surface.

Chemical composition and corrosion resistance of passive chromate films formed on stainless steels 316 L and 1.4301

The chemical composition and corrosion behavior of the natural and formed by chemical treatment in chromium-containing solution passive films on 316 L and 1.4301 stainless steel surfaces have been investigated by means of X-ray photoelectron spectroscopy and electrochemical in situ method of anodic polarization curves. It have been established that the oxide films formed by the chemical treatment have different chemical composition (Cr-enriched), color and reduced corrosion resistance compared to the natural passive films on both steels. The results have shown that the lower part of the oxide layer represents a uniform modified passive film and the upper one is a porous Cr 3+-enriched film with an island-like structure. The latter permits a direct contact of the solution with the modified passive film which controls the corrosion resistance by the dissolution of the Fe 3+ oxides present in the lower thinner layer.

Comparative Study of the Chemical Resistance of Titanium Nitride and Stainless Steel in Media of the Oral Cavity

We have shown that TiN powders practically do not react with biochemical media in the body. Using the polarization curve method, x-ray phase analysis, and Auger-electron spectroscopy of the electrode surface, we have studied the reaction of titanium nitride and 12Kh18N10T stainless steel with distilled water, a 3% solution of NaCl, HCl, and gastric juice. We have demonstrated the high corrosion resistance of both materials in H2O (which is also typical for saliva); but in the presence of salt and when gastric juice is ejected from the esophagus into the oral cavity, the corrosion resistance of steel may decrease by several orders of magnitude compared with TiN. In the case of a titanium nitride electrode, we have also established the mechanism of the protective (inhibiting) action of organic reagents contained in the biochemical media, while stainless steel dissolves in gastric juice significantly more rapidly than in hydrochloric acid with the same pH 2.0.

Electroplating with Chromium–Cobalt Alloy

Electroplating of Cr–Co alloy from sulfate electrolyte based on Cr(III) and Co(II) is studied. The effect of electrolyte composition, pH of solution, and the electrolysis conditions on the alloy composition and the coating quality is shown. The peculiarities of the plating kinetics are studied by a method of partial polarization curves. It is shown that the protective properties of Cr–Co alloy coating are higher than those of chromium and Cr–Fe alloy coatings.

Electrochemical impedance of passive iron in sulfuric acid water-organic solutions

The passive state of iron in sulfuric acid solutions in dimethylformamide and dimethyl sulfoxide containing different amounts of water is studied by the impedance method in a wide range of ac frequencies and also by the methods of polarization curves and open-circuit potential transients. In the studied systems, the metal passivation potential is shown to shift in the positive direction with a decrease in the water content in the solvent. The open-circuit potential of the destruction of the passive layer (Flade potential) is independent both of the nature of the solvents and the water amount in them. The impedance characteristics of passive iron can adequately be modeled by an equivalent circuit consisting of two parallelR-C circuits, i.e. similarly to a circuit used earlier for modeling the impedance of a passive Fe electrode in neutral aqueous solutions. The physical meaning of the equivalent-circuit elements calculated from the impedance measurements is analyzed. The effects the electrode potential, the organic-solvent type, the water content in the latter, etc. have on the elements are discussed. The obtained results suggest that the potential difference applied to the interface between passive iron and studied solutions is located mainly in the Helmholtz layer.

Catalytic decomposition of 3-chloroperoxybenzoic acid by immobilized catalase in a non-aqueous medium.

Catalytic activities of catalase (CAT) immobilized on graphite--GMZ, soot--"NORIT" and "PM-100" to mediate decomposition of 3-Cl-C6H4COOOH (3-CPBA) in acetonitrile have been investigated. Under these conditions, the kinetic parameters Km, k, Ea, Vmax, and Z0 were calculated. Conclusions on a probable mechanism of the catalytic process observed were drawn from the calculated values of deltaG*, deltaH*, and deltaS*. A quantitative UV-spectrophotometrical approach was used as the basic analytical tool. The electrochemical reduction of oxygen generated in enzyme catalysed 3-CPBA decomposition was examined with polarization curves method.

Comparison of polarization curve—and electrochemical quartz crystal microbalance methods for determination of copper corrosion rate

The two methods of determining corrosion rate of copper in different media, polarization curve (PC) and electrochemical quartz crystal microbalance (EQCM), has been compared. The polarization curve method based on Gauss–Newton non-linear fitting was applied to estimate corrosion rate and other electrochemical parameters in the low polarization region. The frequency shift of EQCM during the corrosion process was simultaneously recorded during the polarization process and directly related to the mass change of the copper electrode. The results of electrodeposited copper from these two methods in the solutions with different inhibitors were also compared. It was obvious that the presence of inhibitors including benzotriazole and benzoic acid influenced corrosion rate and other electrochemical parameters. It was found that EQCM was a promising technique in determining corrosion rate for its fast, efficient and reliable operation.