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The purpose of this research is to study different extra-heavy crude oil-in-water emulsions that can be found in practice for corrosion process of X52 steel adding 60 mg.L-1 of non-ionic surfactant and a corrosion inhibitor (CI). Electrochemical impedance spectroscopy and Tafel plots are carried out. Thus, Bode-modulus and Bode-phase angle plots are discussed. Adsorption isotherms obtained from corrosion rate (CR) values are taken into account.

Two-electrode arrangement is used to characterize the pseudo-capacitance values for X52 steel exposed to water and crude oil phases, mainly. Electrochemical evaluations for X52 steel exposed to extra-heavy crude oil-in-water emulsions are recorded in a conventional three-electrode cell to study the corrosion process as was documented in detail by Quej-Ake et al. (2015). Therefore, all electrodes are placed as close as possible to eliminate the iR-drop.

Pseudo-capacitance analysis shows that X52 steel immersed in oilfield produced water was more susceptible to corrosion than that immersed in ocean water solution and extra-heavy crude oil phase. After being analyzed, the X52 steel surface coverage and adsorption process for surfactant and CI could be concluded that surfactant could protect the metal surface. In a coalescence extra-heavy crude oil-in-water emulsion, the water medium generated a new solution that was more corrosive than the original water phase. Wash crude oil process was provoked in emulsion systems to sweep up the salts, mainly. Thus, corrosive species that can be recovered inside extra-heavy crude oil may appear, and in turn a new more corrosive solution could be obtained. Taking into account the straight line obtained in Bode-modulus plot for X52 exposed to extra-heavy crude oil, it is possible to point out that the negative value of the slope or R² can be related to a coefficient (Jorcin et al., 2006). It is important to mention that electrochemical responses for X52 steel exposed to extra-heavy crude oil-in-water under coalescence emulsions revealed that corrosion and diffusion processes exist. Therefore, a possible good inhibitor is surfactant in emulsion systems.

CR and anodic and cathodic slopes suggest that the surfactant acted as mixed CI. Of these, susceptible anodic (MnS and perlite or cementite) and cathodic (ferrite) sites on steel surface could be affected, due to which physicochemical adsorption could happen by using electrochemical parameters analysis. Thus, no stable emulsions should be taken into account for extra-heavy crude oil transportation, because corrosion problems in atmospheric distillation process of the crude oil due to stable emulsion cannot be easily separated. In this manner, coalescent emulsions are more adequate for transporting extra-heavy crude oil because low energy to separate the water media is required.

An electrochemical impedance spectroscopy technique based on an equivalent circuit used for the evaluation of metallic substratum/organic coating/electrolyte systems as well as the importance of each parameter and the way to calculate it is analysed. It is emphasised that the classical semi circumference in the complex plot, which describes the response of a parallel RC circuit, is not real axis centred. This fact makes it necessary to consider the organic film and electrochemical double layer capacitance as pseudo‐capacitances which depend on a fractional power of the frequency. Starting from mathematical relationships over the total impedance algorithms based on the least squares methods are proposed to fit experimental data requiring less processing time than iterative techniques. The methodology is described analysing the charge transfer resistance, ionic resistance and dielectric capacitance variation at increasing immersion times for naval steel/chlorinated rubber (with different PVC)/artificial sea water systems. Parameters thus obtained correlate well with the naval steel/organic coating deterioration with time, also determined by using corrosion potential measurements and visual assessment.

To develop electrode materials for supercapacitor with superior electrochemical performance and simple preparation process, the purpose of this study is to prepare flexible CC/NiS/a-NiS electrodes with self-supporting structure by loading hydrothermally synthesized a-NiS particles along with nano-NiS on carbon cloth by electroplating method.

The effects of current densities, temperatures and pH values on the loading amount and uniformity of the active substances during the plating process were investigated on the basis of optimization of surface morphology, crystalline structure and electrochemical evaluation as the cyclic voltammetry curves, constant current charge–discharge curves and AC impedance.

The a-NiS particles on CC/NiS/a-NiS were mostly covered by the plated nano-NiS, which behaved as a bulge and provided a larger specific surface area. The CC/NiS/a-NiS electrode prepared with the optimized parameter exhibited a specific capacitance of 115.13 F/g at a current density of 1 A/g and a Coulomb efficiency of 84% at 5 A/g, which is superior to that of CC/NiS electrode prepared by electroplating at a current density of 10 mA/cm², a temperature of 55°C and a pH of 4, demonstrating its fast charge response of the electrode and potential application in wearable electronics.

This study provides an integrated solution for the development of specifically structured NiS-based electrode for supercapacitor with simple process, low cost and high electrochemical charge/discharge performance, and the simple and easy-to-use method is also applicable to other electrochemically active composites.

This paper aims to examine the performance of low-pressure cold-sprayed zinc–nickel (Zn-Ni) composites coating, i.e. whether it has the same performance as Zn-Ni alloy coating.

In this paper, Zn-Ni composites coatings containing four different nickel contents were prepared with commercial DYMET 413 low-pressure cold spraying system under the same parameters. Corrosion behaviors of four kinds of coatings were examined with potentiodynamic polarization curves and electrochemical impedance spectroscopy methods, combined with scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.

Corrosion behavior of Zn-Ni composites coating is similar to Zn-Ni alloy coating. In the early stages of immersion, the anodic dissolution of zinc happens, which results in the formation of a zinc hydroxide layer. With the continuous infiltration of chloride ion, zinc hydroxide will get converted to zinc oxide, basic zinc chloride and basic zinc carbonate. The presence of nickel in coatings can prevent zinc hydroxide from converting into zinc oxide.

Further research should be done on improving the deposition efficiency, as the deposition efficiency of low-pressure cold spray is lower than 30 per cent.

Low-pressure cold spray coating can be used in cyclic dry/wet conditions to prolong the life of a steel structure.

Low-pressure cold spray Zn-Ni coating is an environmentally friendly anticorrosion method which can be used as an alternative of hexavalent chromium passivation coating.

Zn-Ni composite coating can be deposited on steel directly by low-pressure cold spray by mechanically mixing the powders together. The composite coating also has the same long-term anticorrosion performance as Zn-Ni alloy coating.

The purpose of this paper is to show that the computation of time-periodic signals for coupled antenna-circuit problems can be substantially accelerated by means of the single shooting method. This allows an efficient analysis of nonlinearly loaded coupled loop antennas for near field communication (NFC) applications.

For the modelling of electrically small coupled field-circuit problems, the partial element equivalent circuit (PEEC) method shows to be very efficient. For analysing the circuit-like description of the coupled problem, this paper developed a generalised modified nodal analysis (MNA) and applied it to specific NFC problems.

It is shown that the periodic steady state (PSS) solution of the resulting differential-algebraic system can be computed very time efficiently by the single shooting method. A speedup of roughly 114 to conventional transient approaches can be achieved.

The proposed approach appears to be an efficient alternative for the computation of time PSS solutions for nonlinear circuit problems coupled with discretised conductive structures, where the homogeneous solution is not of interest.

The present paper explores the implementation and application of the shooting method for nonlinearly loaded coupled antenna-circuit problems based on the PEEC method and shows the efficiency of this approach.

This paper seeks to investigate the different inhibition performance and adsorption behaviour of dodecylamine in acidic and neutral environments and to understand further the inhibition mechanism of dodecylamine in CO₂‐saturated brine solution.

The inhibition performance and adsorption behaviour of dodecylamine on N80 steel in CO₂‐saturated brine solution in acidic and neutral environments were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy and the attenuated total reflection‐Fourier transform infrared spectroscopy.

Corrosion potentials exhibited a pronounced shift in the positive direction at higher concentrations of dodecylamine. The inhibition efficiency of dodecylamine was shown to be pH‐dependent. The effective inhibition concentration of dodecylamine decreased from pH 4.9 to 7.4. In a neutral environment, the inhibitor was shown to affect the deposition of the corrosion products and provide more active sites to bond with the inhibitor. More alkaline environments made the electron cloud density of dodecylamine much higher, which was more favourable to the interaction of dodecylamine and the naked metal base, and hence dodecylamine had a much better inhibition performance in a neutral environment than in acidic environments.

This paper provides information regarding the inhibition performance and adsorption behaviour of dodecylamine on N80 steel and probes the inhibition mechanism of dodecylamine in acidic and neutral environments. The results of the work contribute to an understanding of the inhibition mechanism of the inhibitor in different environments, which will be useful for effective design and choice of inhibitors in CO₂ corrosion.

This paper aims to prepare a composite film on LY12 aluminum (Al) alloy by immersing in dodecyl phosphate and cerium nitrate solution by self-assembling methods. The effect of dipping sequence in dodecyl phosphate and cerium nitrate solution on the corrosion resistance of the composite film is studied.

The corrosion resistance of the dodecyl phosphate/cerium composite film is investigated by electrochemical measurement and film composition analysis.

The dipping sequence in dodecyl phosphate and cerium nitrate solutions has a significant impact on the corrosion resistance of the composite film. It shows best corrosion resistance by first dipping in dodecyl phosphate and then dipping in cerium nitrate solution.

The research shown in this work lays a scientific basis of the film preparation for industrial applications in the future.

The purpose of this study is to investigate the initial corrosion behavior of pure Mg, AZ31 and AZ91 alloys in phosphate buffer solution (PBS) and to characterize the features in corrosion type and resistance of the corrosion product layer.

The scanning electron microscopy, equipped with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy have been used to characterize the as-corroded samples. Besides, the Mg²⁺ concentration in PBSs has been determined by inductively coupled plasma atomic emission spectrum.

It has been found that pure Mg suffers pit corrosion, and AZ31 initially undergoes pit corrosion and then uniform corrosion dominates with an extended immersion duration. However, AZ91 exhibits the uniform corrosion with the highest corrosion rate among the three materials. Besides, the corrosion product layer on AZ31 has the best compactness and corrosion resistance.

The findings add depth in understanding the corrosion of pure Mg and its alloys in PBS and also have guiding significance in exploring the effects by alloyed elements to develop new biomaterials with better performance.

The purpose of this paper is to develop nitrogen-enriched carbon (NC) with high conductivity and specific capacitance as electrode materials for supercapacitors.

Graphene oxide (GO) was synthesized by the modified Hummers–Offeman method. NC was synthesized by carbonization of melamine formaldehyde resin/graphene oxide (MF/GO) composites. Supercapacitors based on Ni(OH)2/Co(OH)2 composites as the positive electrode and NC as the negative electrode were assembled. The electrochemical performances of NC and supercapacitors are studied.

The results show that obtained NC has high nitrogen content. Compared to NC-GO0 without GO, high conductivity and specific capacitance were obtained for NC with GO due to the introduction of layered GO. The presence of pseudocapacitive interactions between potassium cations and the nitrogen atoms of NC was also proposed. When the weight ratio of GO to MF is 0.013:1, the obtained NC-GO3 has the highest specific capacitance of 154.07 F/g due to GO and its highest content of N-6. When the P of the asymmetric supercapacitor with NC-GO3 as the negative electrode is 1,326.70 W/kg, its Cps and Ep are still 23.84 F/g and 8.48 Wh/Kg, respectively. There is only 4.4 per cent decay in Cps of the supercapacitor over 1,000 cycles.

NC is a suitable electrode material for supercapacitors. The supercapacitors can be used in the field of automobiles and can solve the problems of energy shortage and environmental pollutions.

NC based on MF/GO composites with high nitrogen content and conductivity was novel and its electrochemical properties were excellent.

The purpose of this paper is to reveal the mechanism of nitrite (NO_2⁻) for the surface passivation of carbon steels in acidic environments through investigating the influences of 0.01 mol/L NaNO₂ addition on the corrosion and passivation behaviors of Q235 carbon steel in acidic phosphate buffer (APB) solutions (pH 2 to 6).

The electrochemical techniques including open circle potential evolution, potentiodynamic polarization, electrochemical impedance spectroscopy and cyclic voltammetry were applied.

In APB solutions without NO_2⁻, the Q235 steel presented the electrochemical behaviors of activation (A), activation-passivation-transpassivation and self-passivation-transpassivation at pH 2 to 4, pH 5 and pH 6, respectively; the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6.

In APB solutions without NO_2⁻, the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6. With the addition of 0.01 mol/L NaNO₂, into APB solutions, the variation of corrosion rate showed the same rule, but the surface passivation occurred over the whole acidic pH range, including the anodic passivation at pH 2 to 4 and the spontaneous passivation at pH 5 to 6.