Iron In Sulfuric Acid Research Articles

Corrosion Resistance of Modified Amorphous Alloys Based on Iron in Sulfuric Acid

Corrosion Resistance of Modified Amorphous Alloys Based on Iron in Sulfuric Acid

Synchronization in populations of electrochemical bursting oscillators with chaotic slow dynamics.

We investigate the synchronization of coupled electrochemical bursting oscillators using the electrodissolution of iron in sulfuric acid. The dynamics of a single oscillator consisted of slow chaotic oscillations interrupted by a burst of fast spiking, generating a multiple time-scale dynamical system. A wavelet analysis first decomposed the time series data from each oscillator into a fast and a slow component, and the corresponding phases were also obtained. The phase synchronization of the fast and slow dynamics was analyzed as a function of electrical coupling imposed by an external coupling resistance. For two oscillators, a progressive transition was observed: With increasing coupling strength, first, the fast bursting intervals overlapped, which was followed by synchronization of the fast spiking, and finally, the slow chaotic oscillations synchronized. With a population of globally coupled 25 oscillators, the coupling eliminated the fast dynamics, and only the synchronization of the slow dynamics can be observed. The results demonstrated the complexities of synchronization with bursting oscillations that could be useful in other systems with multiple time-scale dynamics, in particular, in neuronal networks.

Study of the Behavior of Sodium Diclofenac Expired Drug as an Corrosion Inhibitor of Iron in Sulfuric Acid Using UV-VIS Spectrophotometry

The effect of Sodium Diclofenac (SD) as an inhibitor of pure iron corrosion in a 1.0 N of sulfuric acid was studied spectrally using a UV-VIS at different temperatures of 343.15, 323.15, 303.15 K. The concentration of dissolved iron was determined spectrally using phenanthroline method. The absorbance of each solution was measured at different times, and the data obtained were used to calculate the corrosion rate, which was found to be a zero-order reaction in the presence and absence of the SD inhibitor. The absorbance was decreased with an increase in inhibitor concentration and an increase in temperature. However, the inhibition efficiency was increased with inhibitor concentration an increase. The inhibitor is adsorbed on the surface of the iron particles according to the Langmuir and Kinetic-thermodynamic model of adsorption isotherm. The results indicated that the reaction is endothermic and unspontaneous. Quantum chemical parameters such as the highest & lowest occupied molecular orbital energy (EHOMO) & (ELUMO), energy gap (ΔE), were calculated and correlated to the experimental data.

Iron sulphates production being polarized by the direct and alternating currents

The process of iron oxidation in the sulfate electrolytes was studied by the method of electrochemical polarization by the steady and transient currents. Initially, in the first electrolyzer, the iron electrodes were oxidized under the influence of alternating current. The results of iron oxidation in the first electrolyzer were monitored by determining the weight loss of the iron electrodes. An almost rectilinear increase in the mass of iron is established to be observed, which passed into the solution in the form of Fe2+ ions when the current density changes in the range of 80-400 A / m2. The current efficiency is close to 100%, and sometimes exceeds 100%, since the chemical dissolution of iron in sulfuric acid also occurs simultaneously. The iron sulfate (II) can be obtained by evaporation of the solution. After that, the sulfate solution containing iron ions (II) was sent to the second electrolyzer, in which the oxidation of iron (II) to iron (III) was carried out under the direct current. The electrode spaces were separated by an MA-40 anion exchange membrane. Over 90% of iron (II) was demonstrated to be transfers into the trivalent state within 1 hour in the second electrolyzer at a current density of 120 A / m2. A change in the current density to 600 A / m2 leads to an increase in the oxidation state to 97.5%, i.e. iron ions (II) are almost completely oxidized under the specified conditions. As a result of the experiments, an electrochemical method for producing iron sulfate (III) was developed.

Anodic Polarization Behavior of Iron in Phosphoric Acid Solution Under the Action of Magnetic Field

The effect of magentic field on anodic dissolution, passivation and dissolution-passivation transition of iron in sulfuric acid solutions have been investigated. The change of anodic dissolution in the dissolution-passivation transition region and the resultant shrinkage of the passive region due to applied magnetic field have been reported. Uneven dissolution of iron electrode after anodic dissolution in sulfuric acid solutions have been reported. In the represent work, the effect of magnetic field on anodic behavior of iron in 0.5 mol/L phosphoric acid is investigated. Potentiodynamic polarization curves and potentiostatic polarization measurements are conducted at 0T and 0.4T. The anodic polarization curves at 0T and 0.4T are shown in Fig. 1, and the electrode surfaces after the measurements are shown in Fig. 2. The anodic polarization curve at 0T exhibits typical anodic dissolution, dissolution-passivation transition, steady passivation and transpassivation behavior. There is no sgnificant effect of magentic field on the active dissolution at potentials lower than Emax, 0T. Magnetic field moves the dissolution-passivation transition potential to a more noble potential therefore narrows the steady passivation range. There is no passive range in the anodic polarizaiton curve at 0.4T, showing only the drastic drop of current at Emax, 0.4T and then an increase of current soon. There is a quasi-linear potential-current density relationship in a wide potential range, i.e. -0.45 to 0.90V(SCE) at 0T, and -0.45 to 1.85V (SCE). The electrode surfaces after the potentiodynamic polarization measurements up to 2.0V(SCE) at 100 mV/min are observed, indicating severe anodic dissolution. The uneven electrode surface shows the locally accelerated anodic dissolution at the left and right edges of the electrode. From the center of the electrode along the horizontal direction to the edge, the uneven dissolution of the electrode surface presents an aggravating tendency. The results are consistent with thoese observed for iron in sulfuric acid at 0.4T magnetic field. When potentiostatic polarization starts at 1.2V at 0T, passive state can be reached and the further applied 0.4T magnetic field decreased the measured current density, showing the potential-dependent rate determining step and the resultant magnetic field effect on selective electrochemical processes. Figure 1

Experiments on electrical resonance and antiresonance of the electrochemical interface under potentiostatic control

The ability of electrochemical interfaces to exhibit electric resonance and antiresonance is studied experimentally. The system under investigation is the electrodissolution of iron in sulfuric acid. The impedance of the system in the vicinity of a Hopf bifurcation is studied while the system rests on a steady state of a stable focus type. The frequency response is explored for different values of the solution concentration as well as different external ohmic resistance values. It is shown that the system undergoes electrical resonance and antiresonance at frequency values determined by the system parameters and thus acts as a resonator (band-pass filter) or wave trap (band-stop filter).

Investigation of the effect of piperidin-1-yl-phosphonic acid on corrosion of iron in sulfuric acid

The inhibitive effect of the piperidin-1-yl-phosphonic acid (PPA) on the corrosion of iron in 1M H2SO4 solution has been investigated by weight loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The presence of (PPA) reduces remarkably the corrosion rate of iron in acidic solution. The effect of temperature on the corrosion behavior of iron was studied in the range of 298–328K. Results clearly reveal that the (PPA) behaves as a mixed type corrosion inhibitor with the highest inhibition at 5×10−3M. The adsorption of PPA on the iron surface obeys the Langmuir's adsorption isotherm.

Synchronization properties of coupled electrochemical bursters

In the present paper the non-linear time evolution of the electrodissolution/passivation of iron in sulfuric acid–sodium chloride solution is explored. The working electrode is an assembly of two iron disk electrodes, interacting through the electrolyte, and the time evolution of the electric current has the form of spontaneous bursting oscillations. The main aim of this work is to characterize the modes of synchrony and more specifically the synchronization of electric bursts and the synchronization of electric spikes. The characterization is based on the calculation of the firing rates from the experimental time series and the extraction of the slow dynamics by low-pass filtering. The analysis is performed both for elliptic and square wave electrochemical bursting and the results are compared with neural oscillations.

Single and coupled electrochemical bursters during the electrodissolution/passivation of iron

The ability to produce bursting electrochemical oscillations via the slow external variation of the applied potential is investigated during the electrodissolution/passivation of iron in sulfuric acid. The results are compared with those concerning spontaneous electrochemical bursting in the presence of chloride ions. Moreover, an assembly of two electrochemical Fe/H 2SO 4bursters is studied experimentally. The effect of phase space topology on synchrony is explored by studying the coupled response for different types of electrochemical bursters.

Anticorrosion Behaviors of Quaternary Polyethyleneimine in Acidic Environment

Polymeric compounds are of great interest as corrosion inhibitors in acidic environment due to their inherent stability. Polymeric film is effectively used for the protection of metals partly owing to their capacity to act as a physical barrier between the metal surface and the corrosive environment. In this paper, a cation polyelectrolyte inhibitor (Quaternary Polyethyleneimine, QPEI) was prepared. The quality and inhibition efficiency of QPEI self-adsorbed films were studied by polarization curve and electrochemical impedance spectroscopy, respectively. The compositions and morphologies of the polymer film on the steel surface were examined with the aids of SEM and XPS, respectively. The results showed that QPEI could greatly retard the corrosion of iron in sulfuric acid, which was attributed mainly to the protective QPEI film formed on the surface. Meanwhile, the inhibition of QPEI could be supposed as a mixed process, in which both cathodic and anodic corrosions were simultaneously restrained. Based on the results of XPS and SEM, it could be evidenced that the QPEI can form a protective polymer layer on the metal surface by adsorption.

Digital holographic study of the effect of magnetic field on the potentiostatic current oscillations of iron in sulfuric acid

The effect of magnetic field on the potentiostatic current oscillations of iron electrode in 0.5 mol dm−3 sulfuric acid was studied in situ by digital holography. The orientation of the magnetic field had an obvious effect on the current oscillations: when the magnetic field was vertical to the electrode surface, the magnetic field would cause a cyclotron-like fluid flow of ions and had a negligible effect on mass transport and the oscillations; when the magnetic field was parallel to the electrode surface, the force would drive the charging ions to one side of the electrode and increase the mass transport, resulted in a decrease of oscillation period. The effects were analyzed by holograms and discussed by means of magnetohydrodynamic force.

Bursting Oscillations during Metal Electrodissolution: Experiments and Model

Experiments were carried out on bursting oscillations in an electrochemical system, the dissolution of iron in sulfuric acid. Bursting characteristics were investigated as functions of the parameters applied potential and external resistance. We develop a model that incorporates the effects of oxide and salt films. This model reproduces all the important features of the dynamics seen in experiments including both the slow active−passive oscillations and the faster oscillations on the mass-transfer-limited plateau as well as the bursting phenomena. During this bursting, two time scales are important: the slow variation of the salt-film thickness and the faster dynamics of a three-variable (potential drop and proton and iron(II) concentrations) subsystem.

Synergistic Effects of Benzotriazole and Copper Ions on the Electrochemical Impedance Spectroscopy and Corrosion Behavior of Iron in Sulfuric Acid

Benzotriazole (BTAH) and copper ions exhibit synergistic effects on the electrochemical impedance spectroscopy and corrosion behavior of iron in sulfuric acid. The presence of submicro- and micromolar amounts of Cu2+ ions along with millimolar amounts of BTAH caused order of magnitude increases in the polarization resistance of the iron/acid interface, above those caused by either BTAH or Cu2+ ions (which is equivalent to order of magnitude decreases in the corrosion rate). This was accompanied by a significant decrease in the capacity of the electrical double layer of the interface, which also showed synergistic effects. The results are interpreted in terms of the deposition, on the iron surface, of a protective film composed of a polymeric complex formed from copper ions and adsorbed BTAH that is believed to be of the form [Cu(I)BTA]n. This film inhibits the cathodic partial (hydrogen evolution) reaction, which is the rate-determining step (rds) and hence the overall corrosion reaction. An increase in the concentration of either Cu2+ or BTAH enhances this synergistic effect. However, there is a critical concentration of copper ions (5 × 10-6 M) beyond which further increase decreases the magnitude of the synergistic effect. This is attributed to deposition of metallic copper on the iron surface at higher concentrations of Cu2+ ions, which promotes the rds and hence the overall corrosion reaction. The results are supported by measurements of polarization curves and mass loss under various conditions.

Electrochemical study of the adsorption and inhibiting properties of halogen derivatives of aniline on iron in sulfuric acid

The adsorption of halogen derivatives of aniline on an iron electrode in sulfuric acid medium has been studied in relation to their inhibiting properties using electrochemical a.c. impedance and d.c. polarization techniques, as well as quantum chemical calculations of chemical structure and distribution of electron charges in the organic molecules. It is established that the adsorption process is described by Frumkin's isotherm. The adsorption parameters characterizing the interaction forces between the molecules in the adsorbed layer, the free energy of adsorption, the maximum surface excess of adsorbed species, the area occupied by each molecule etc. have been calculated on the basis of this isotherm. It is shown that the inhibition efficiency, as well as the free energy of adsorption, increases in the sequence: aniline < p-Cl-aniline < p-Br-aniline < p-I-aniline. It was found that the adsorption behaviour of the substances studied is characterized by two adsorption states: vertical and planar orientation of the molecules. Combining data from electrochemical measurements with data from quantum chemical calculations the correlation between the chemical structure of the aniline derivatives and their adsorption capability and inhibition efficiency has been ascertained.

The Effect of Several Anions and Inhibitors Mixed with Propargyl Alcohol on Electrode Reactions and Corrosion of Steel in Sulfuric Acid

The effect of arsenate- and halide-ions, sulfur-containing compounds, and a nitrogen-containing inhibitor on the inhibition of the corrosion of steel Ст3 and electrode reactions on iron in sulfuric acid by propargyl alcohol (PA) is studied with the use of weighing and various potentiostatic polarization. None of the additives completely suppress the process of cathodic hydrogenation of PA. It is advisable to apply PA in small concentrations with the addition of rhodanide-ions and Captax.

N,N-Dipropynoxy methyl amine trimethyl phosphonate as corrosion inhibitor for iron in sulfuric acid

The corrosion inhibition of iron in 0.5 M sulfuric acid by N, N-dipropynoxy methyl amine trimethyl phosphonate has been investigated by means of the potentiodynamic polarization and electrochemical impedance spectrum (E.I.S) techniques. N,N-dipropynoxy methyl amine trimethyl phosphonate was studied in concentrations from 40 ppm to 320 ppm at a temperature of 298 K. The results show that the inhibition mechanism of N,N-dipropynoxy methyl amine trimethyl phosphonate is mixed controlled. It is also found that this inhibitor obeys the Frumkin adsorption isotherm and Flory-Huggins isotherm based on a substitutional adsorption process.

A Study on Stochastic Resonance for the Process of Active-passive Transition of Iron in Sulfuric Acid

A Study on Stochastic Resonance for the Process of Active-passive Transition of Iron in Sulfuric Acid

An investigation of the potentiostatic current oscillation during the anodic dissolution of iron in sulfuric acid

A dynamical system analysis is presented to disclose the origin of current oscillation during the anodic dissolution of iron in sulfuric acid. The threshold of the electrochemical oscillatory dynamical regime is discussed in the parameter plane. The necessary electrode potential for oscillation increases as the stirring speed of the electrolyte solution increases and there is a critical stirring speed above which stable limit cycle oscillation cannot appear. The polarization curve is calculated and there is a limiting current plateau. There is an electrode potential interval within which the non-equilibrium steady state is unstable and the system oscillates before the potential reaches the limiting current plateau region. The limiting current increases with increasing stirring speed.

Metastable Pitting and the Critical Pitting Temperature

For any particular stainless steel, a critical pitting temperature (CPT) can be measured, below which stable pits do not occur at any potential up to the onset of transpassivity. The more highly alloyed the steel, particularly with molybdenum, the higher the CPT. The CPT for 904L austenitic stainless steel with a 240 grit surface finish has been determined as 48 to 49°C, and metastable pitting events have been analyzed in detail at lower temperatures. Below the CPT, metastable pitting activity peaks at around 300 mV (SCE), but occurs at all potentials up to the transpassive range. The morphology of these pits has been examined using SEM and a model is proposed in which precipitation of an anodic salt film within pits is the critical factor; above the CPT, a salt film is essential for stable pit growth, while below the CPT, the salt is an intermediary in oxide passivation, like that of iron in sulfuric acid. This is an outcome of a complex dynamical system and does not require the properties of the salt itself to change suddenly with temperature.

Quantitative Analysis of Iron Dissolution during Repassivation of Freshly Generated Metallic Surfaces

A channel flow double electrode was coupled with the pulsed laser depassivation technique to investigate the repassivation kinetics on iron in sulfuric acid (pH 1 to 3). The amount of ferrous ion dissolved from the activated iron electrode during repassivation was measured. The total charge for repassivation is separated into partial charges for dissolution of ions, Qd, and formation of adsorbed species, Qf. The charge Qd decreases with the electrode potential. The charge Qf does not depend on the electrode potential. Its value corresponds to the formation of a monolayer of trivalent oxide film. A reaction model for repassivation of iron involving two adsorbed species was simulated numerically in good agreement with the experimental results. The actual rate of repassivation was characterized by the fractional coverage of passivating species.