Potentiostatic corrosion protection technology under cavitation condition for 5083-H116 Al alloy

This study aims to characterize the cavitation damage behavior of aluminum alloys in seawater and thus to enhance its cavitation resistance. Potentiostatic experiments were performed under various potential conditions to determine the optimum protection potentials, at which cavitation damage was suppressed. A potential range was selected for the experiment from -2.2 to -1.4 V, which corresponded to the concentration and activation polarization regions on the cathodic polarization curve of the 5083-H116 alloy. After the experiments, the current density-time behavior was investigated, and the degree of surface damage was observed using three-dimensional microscopy and scanning electron microscopy （SEM）, The optimum protection potential was determined to be in the range of-l.9 to -1.5 V under which the cavitation damage was reduced significantly.

Optimization of the thermoelectric properties of poly(nickel-ethylenetetrathiolate) synthesized via potentiostatic deposition

The coordination polymer poly（nickel-ethylenetetrathiolate） （poly（Ni-ett））, formed by nickel（Ⅱ） and 1,1,2,2-ethenetetrathiolate （ett）, is the most promising N-type organic thermoelectric material ever reported; it is synthesized via potentiostatic deposition, and the effect of different applied potentials on the optimal performance of the polymers is investigated. The optimal thermoelectric property ofpoly（Ni-ett） synthesized at 0.6 V is remarkably greater than that of the polymers synthesized at 1 and 1.6 V, exhibiting a maximum power factor of up to 131.6μW/mK2 at 360 K. Furthermore, the structure-property correlation ofpoly（Ni-ett） is also extensively investigated. X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） analyses revealed that the larger size of crystalline domains and the higher oxidation state of poly（Ni-ett） synthesized at 0.6 V possibly results in the higher bulk mobility and carrier concentration in the polymer chains, respectively, accounting for the enhanced power factor.

Anodic hydrogen evolution on Mg

We measured the anodic hydrogen evolution rates for various applied anodic current densities and estimated the corresponding cathodic hydrogen evolution rates.The estimated cathodic hydrogen evolution rates were less than the measured anodic hydrogen evolution rates,contradicting the enhanced catalytic activity mechanism of Mg corrosion.In addition,this model was contradicted by the measured apparent Mg valence of 1.2±0.1.In contrast,the uni-positive Mg^(+)mechanism of Mg corrosion was supported by(i)the apparent Mg valence of 1.2±0.1,and(ii)the fact that the measured anodic hydrogen evolution rate increased with increasing weight loss rate.

An electrochemical method for evaluating the resistance to cathodic disbondment of anti-corrosion coatings on buried pipelines

Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some disadvantages and the evaluated results are only simple figures and always rely on the subjective experience of the operator. A new electrochemical method for evaluating the RCD of coatings, that is, the potentiostatic evaluation method （PEM）, was developed and studied. During potentiostatic anodic polarization testing, the changes of stable polarization current of specimens before and after cathodic disbonding （CD） were measured, and the degree of cathodic disbondment of the coating was quantitatively evaluated, among which the equivalent cathodic disbonded distance AD was suggested as a parameter for evaluating the RCD. A series of testing parameters of the PEM were determined in these experiments.

Influence of particle size and surfactants on uniformity and quantity of silicon carbide particles in electrodeposited nickel-silicon carbide coatings

The electrodeposition of nickel-silicon carbide coatings on a copper electrode was done by mixing SiC particles in the nickel electrodeposition solution.The influence of surfactants and silicon carbide particle size on uniformity and quantity of silicon carbide particles in nickel-silicon carbide composite coatings was investigated.It was found that particle size affects the nucleation overpotential,with 40 nm silicon carbide nanoparticles more effective in promoting nickel nucleation than 500 nm particles due to an increase in active nucleation sites.In terms of surfactants,anionic surfactant sodium dodecyl sulfate(SDS)produced better dispersion of 40 nm silicon carbide particles than cationic surfactant cetyltrimethyl ammonium bromide(CTAB),but little difference was found between the two when 500 nm silicon carbide particles were used.Thus,although the suspension of silicon carbide particles can be improved and their co-deposition can be promoted with a cationic surfactant CTAB,it is less effective than an anionic surfactant SDS in terms of surface finish.

The Crevice Corrosion of 316<i>L SS</i>Alloy in NaCl Solution at Different Applied Potentials

316L SS alloy was tested under different applied potentials to study the susceptibility of this alloy to crevice corrosion. XPS measurements have been carried out to detect and define the products which formed on the surface of 316L SS in 3.5% NaCl at room temperature at applied potential = 200 mVSCE. The formation of Fe, Cr and Mo compounds were found, and these compounds play a great role in protecting the alloy which was found. The boundaries of the corroded area under washer teeth are in agreement with IR drop. The potentiodynamic technique is also studied to examine the overall corrosion behavior of 316L SS.

Fast Determination of Vitamin B₂Based on Molecularly Imprinted Electrochemical Sensor

Under the condition of weak acidity of pH 5.2, a sensitive vitamin B2 electrochemical sensor based on molecularly imprinted nonconducting polymer of o-aminophenol by potentiostatic polymerization in the presence of template(vitamin B2) on a glassy carbon electrode was prepared, and its performance was studied. The sensor exhibited good sensitivity and selectivity to VB2. The detection limit went down to 2.3851nM, and a linear relationship between the current incremental and the concentration was found in the range of 10~120nM. And the sensor could use in detection of VB2 real sample for a long time and show good reproducibility. The average recovery rate to VB2 was 98.41%.

Study on Electrodeposition of Ho-Co Alloy in Dimethylsulfoxide

Co deposition of Ho with Co was studied in dimethylsulfoxide (DMSO) by cyclic voltammetry and potentiostatic deposition at room temperature. The cyclic voltammogram shows that the codeposition of Ho with Co can be attributed to induced codeposition mechanism, for the codeposition potential is more negative than the deposition potential of Co but positive than that of Ho. For the potentiostatic deposition used in Ho Co alloys preparation, the results indicate that in the range of selected concentration the potential is the main factor determining the content of Ho in Ho Co alloys, while the composition of Ho 3+ and Co 2+ in electrolyte solution has less influence. According to the analysis of X ray diffraction, EDAX, and scanning electron microscopy, uniform, compact and amorphous films on Cu can be obtained at -1 8 V (vs.SCE) in 0 165 mol·L -1 Ho(NO 3) -0 135 mol·L -1 CoCl 2 DMSO solution.

Electrochemistry of Hf(Ⅳ)in NaCl-KCl-Na-K_(2)HfF_(6) molten salts

The cathodic reduction mechanism of Hf(Ⅳ)ions in a fused Na Cl–KCl–Na F–K_(2) HfF_(6) salt system was studied in various Na F concentrations at 1073 K to obtain a purified dendritic Hf metal.The results of cyclic voltammetry and square wave voltammetry indicated that the reduction process comprised two steps of Hf(Ⅳ)→Hf(Ⅱ)and Hf(Ⅱ)→Hf at low Na F concentrations(0<molar ratio of[F-/Hf 4+]≤17.39)and one step of Hf(Ⅳ)→Hf at high Na F concentrations(17.39<molar ratio of[F-/Hf 4+]<23.27).The structure and morphology of the deposits obtained in potentiostatic electrolysis in the one-step reduction process were analyzed and verified by X-ray diffraction,scanning electron microscopy,and energy dispersive X-ray spectrometry.In the one-step reduction process,the disproportionation reaction between the Hf metal and Hf complex ions was inhibited,and a large dendrite Hf metal was achieved in molten salt electrorefining.

Modeling of Amperometric Immunosensor for CMOS Integration

A circuit model of the Amperometric immunosensor for use in the biosensor system-on-chip simulation is proposed in this paper.The model parameters are extracted with several methods and verified by MATLAB and SPICE simulation.A CMOS potentiostat circuit required for conditioning the Amperometric immunosensor is also included in the circuit model.The mean square error norm of the simulated curve against the measured one is 8.65×10^(-17) The whole circuit has been fabricated in a 0.35μm CMOS process.

Application of Potentiostats Using PC in the Phase Analysis of Galvano-Chemis-try

A set of device is designed based on PC to realize the functions of traditional potentiostats in the phase ana1ysis of galvanochemistry. In the device, A/D and D/A conversion is used to measure the electrode potential and convert the voltage for outPut; specific program runs in the PC to regulate and control the system. The effect of the proportion factor Kp on the control variation is researched through certain experiment. Two experiments, the control of electrolysis in constant poteniial and the determination of polarization curves, are designed to test and evaluate the effectiveness of the device. The experimemel results show that the variation between the actualanode potential and the target potential could be controlled to below 1 mV if Kp is set to an appropriate value.

Corrosion of Snails (Gastropods) in Acidic Environment and Their Protection

Snails’ protection is essential because this species is to maintain a balanced ecology of water sources. They occur in rivers as well as ponds and balance the pH level of water. But these sources of water are contaminated by effluents, pollutants, acid rain, particulates, biological wastes etc. They can change the pH of water. Water is absorber of carbon dioxide and it converts carbon dioxide into carbonic. Other above mentioned wastes also increase the concentration of H+ ions in water. They produce hostile environment for snails. The outer part of snails is made of CaCO3. It produces chemical reaction in acidic medium and corrosion reaction is accelerated, and thus deterioration starts on the surface of snails. This medium makes their survival become miserable. For this work, corrosion of the snails’ study in the pH values of water is 6.5 in H2CO3 environment. The corrosion rates of snails were calculated by gravimetric methods and potentiostat technique. Aloe Vera was used for corrosion protection in acidic medium. The surface adsorption phenomenon was studied by Langmuir isotherm. Aloe Vera formed thin surface film on the interface of snails which adhered with chemical bonding. It was confirmed by activation energy, heat of adsorption, free energy, enthalpy and entropy. The results of surface coverage area and inhibitors efficiency indicated that Aloe Vera developed a strong protective barrier in the acidic medium.

Corrosion Behaviour of Al6061-Frit Particulate Metal Matrix Composites in Sodium Chloride Solution

In this investigation, an attempt has been made to develop Al6061-Frit particulate metal matrix composites through stir casting technique using metal molds and to study the corrosion behaviour. Pre heated frit particles were added to matrix as reinforcement. Al6061 containing 2 wt% to 8 wt % in steps of 2 wt % of frit particulate composites were prepared. Corrosion tests were conducted by using Potentiostat model SEP238C where 3.5% NaCl solution was used as corrodent. The corrosion rate of metal matrix composites was lower than that of matrix material Al6061 under the corrosive atmosphere for both un-heat treated and heat treated conditions.

DEVELOPMENT OF A PRECISE ELECTRO CHEMICAL INTERFACE

Based on the circuit principle of 1186 Electro Chemical Interface preduced by Solartron Electronic Group Ltd., a precise electro chemical interface (ECI) unit, which can provide the interfacing requirements for the control and measurement of characteristics of electro chemical cell, was developed by means of some essential improvements. Not only can it be used to control and measure the steady and non-steady state characteristics, but also it can be directly connected with Solartron 1170 series or 1250 Frequency Response Analysers (FRA) to measure the AC impedance. Besides,the EC1 can also be connected with two- or three-electrode electro chemical cell systems to test convenlently and correctly their DC and AC characteristics, and used as a four-electrode potentlostat combined with four-electrode electro chernical cell system which contains two reference electrodes (RES) for researches on the electro chemical characteristics of oil-water interface, etc.

A Simplified Microcontroller Based Potentiostat for Low-Resource Applications

A low component count, microcontroller-based potentiostat circuit was developed through the use of operational amplifiers arranged in different feedback configurations. This was developed to alleviate the cost burden of equipment procurement in low-cost and budget applications. Simplicity was achieved in the design by the use of the microcontroller’s native functionalities and a low-cost R/2R resistor ladder digital-to-analogue converter. The potentiostat was used to investigate the Ni2+/Ni(s) redox couple in a 3-electrode cell with a silver/silver chloride reference electrode and graphite counter and working electrodes. Linear sweep voltammograms were ob-tained at scan rates of 10, 20, 30 and 40 mV/s. The analysis of the peak current versus (scan rate)1/2 plot indicated that the Ni2+/Ni(s) reduction, though conforming to the Randles-Sevcik equation, was a non-reversible redox reaction.

Effect of Radial Expansion of Cr-Mo Steel Tubes on Their Corrosion Behavior in Sea Water

This paper studies the effect of expansion ratio on the corrosion rate of the expanded tubes exposed to sea water as well as the microstructure changes caused by the expansion of Cr-Mo steel tubes to large permanent deformations. 2.25 Cr-1.0 Mo steel (schedule 40 and schedule 80) tubes were subjected to various expansion ratios of 10%, 15%, 20%, and 25% by pushing conical mandrels through them using a piston. The microstructure was also studied to determine the effect of the expansion on the grain structure of the material. Microscopic examination of the expanded tubes revealed that grains elongate along the direction of the hoop stress and this elongation increases with an increase of expansion ratio. Moreover, it was found that corrosion rate and hardness increase with an increase in expansion ratio.

Electrochemical behavior of Fe(Ⅲ)in Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)molten salt

The high-temperature requirement for liquid iron smelting via molten oxide electrolysis presents significant challenges.This study investigates the electrochemical reduction of Fe(Ⅲ)in a novel low-temperature electrolyte,Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3),utilizing cyclic voltammetry and square wave voltammetry techniques.The results show that Fe(Ⅲ)reduction occurs in two steps:Fe(Ⅲ)+e^(−)→Fe(Ⅱ),Fe(Ⅱ)+2e^(−)→Fe,and that the redox process of Fe(Ⅲ)/Fe(Ⅱ)at the tungsten electrode is an irreversible reaction controlled by diffusion.The diffusion coefficients of Fe(Ⅲ)in the molten Na_(2)SiO_(3)-SiO_(2)-Fe_(2)O_(3)in the temperature range of 1248–1278 K are between 1.86×10^(−6)cm^(2)/s and 1.58×10^(−4)cm^(2)/s.The diffusion activation energy of Fe(Ⅲ)in the molten salt is 1825.41 kJ/mol.As confirmed by XRD analysis,potentiostatic electrolysis at−0.857 V(vs.O_(2)/O_(complex)^(2-))for 6 h produces metallic iron on the cathode.

Electrochemical behavior of Y(Ⅲ) and preparation of Y-Ni intermetallic compounds in molten LiCl-KCl salts

The work concerned the electrochemical behaviors of Y（Ⅲ） on W and Ni electrodes in molten LiCl-KCl salts by a series of electrochemical techniques. The electrochemical reaction of Y（Ⅲ） to Y（0） proceeded in a one-step reduction process with the exchange of three electrons, Y（Ⅲ）＋3e^–→Y（0）. Compared with the cyclic voltammogram and square wave voltammogram obtained on W electrode, the reduction potential of Y（Ⅲ） on Ni electrode was observed at less negative potential than the one of Y（Ⅲ） to give pure Y metal on W electrode, which revealed the occurrence of underpotential deposition of Y（Ⅲ） on Ni electrode. Electromotive force（emf） measurements were performed to calculate the relative partial molar Gibbs energies and activities of Y in Y-Ni alloys. The standard Gibbs energies of formation for different Y-Ni intermetallic compounds were also estimated. The different Y-Ni alloys were formed by potentiostatic electrolysis at different potentials and characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy dispersive spectrometry（EDS）. It was found that four intermetallic compounds, YNi5, Y2Ni7, YNi3 and YNi2, were selectively produced by controlling applied potential.

Effect of applied potential on the microstructure, composition and corrosion resistance evolution of fluoride conversion film on AZ31 magnesium alloy

AZ31 magnesium（Mg） alloy was potentiostatic polarized in 0.1 M deaerated KF solution with pH 7.5 from-0.4 V to-1.4 V with an interval of-0.2 V. The polarization process was described by the potentiostatic current decay. The resultant film was analyzed by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS） and electrochemical impedance spectroscopy（EIS）. The results demonstrated that the deposited film included a Mg（OH）2/MgF2 containing inner layer and a Mg（OH）-2/MgF2/KMgF3 comprising outer layer. The high polarized potential produced high content of MgF2 but low content of KMgF3 and thin film. Conversely, the low polarized potential produced small content of MgF2 but high content of KMgF3 and thick film. The optimal corrosion resistance of the deposited film was obtained at-1.4 V, which was closely related with the content of MgF2 and KMgF3 and the film thickness.

Effect of Vacuum Pressure on the Initiation and Propagation of Pitting Corrosion of 2205 Duplex Stainless Steel in Concentrated Seawater

Pitting initiation and stable propagation behaviors of 2205 duplex stainless steel were investigated in the hot concentrated seawater under vacuum pressures by potentiostatic polarization. Both applied potentials and vacuum pressures greatly influence the pitting corrosion. Higher potentials lead to much faster stable pitting initiation and growth rates in both static(101.3 kPa) and dynamic(28.4 kPa) solutions. The pressure reduction can also accelerate the pitting initiation rate. However, the boiling of solution can influence the pitting propagation mechanism. The dynamic actions of boiling bubbles are unfavorable to the pit propagation and result in the formation of relatively smooth pit bottom without secondary pits.