Potentiodynamic Technique Research Articles

Study of the air-formed oxide layer at the copper surface and its impact on the copper corrosion in an aggressive chloride medium

The electrochemical behaviour of pre-oxidized copper surfaces prepared by heating in air at 90 °C was studied to evaluate the impact of the air-formed oxide layer at the copper surface on the corrosion in an aggressive chloride medium. In a first part, the evolution of the chemical composition and the structure of the air-formed oxide layer with the heating time were investigated by cyclic voltammetry in an alkaline medium in which the different oxide species can be discriminated, X-ray photoelectrons spectroscopy experiments (XPS) and water contact angle measurements. It was demonstrated that short heating times produce Cu2O-rich films, while CuO-rich films were obtained after long heating-time periods. Furthermore, cyclic voltammetric data strongly support a stratification of the corrosion products in the mature oxide layer. In a second part, the protection efficiency of air-formed films, aged from 1 to 22 days, against the copper corrosion was study using a potentiodynamic technique and the electrochemical impedance spectroscopy (EIS) in an aerated 0.2 M NaCl aqueous electrolyte. Results demonstrate that the chemical composition of the air-formed oxide layer has an important impact in the overall corrosion process. Results are tentatively explained in terms of composition and structure of the oxide layer.

Titanium Silicon Oxide Nanoflower Coated Polyaniline Nanocomposite for Enhancement of Corrosion Protection Performance on Mild Steel

In this study PANI/titanium silicon oxide (PTS) nanoflower coated nanofiber has been synthesized by chemical oxidation method. PANI nanocomposite has been applied as a corrosion protective material which helps in improving the corrosion resistance of various metal oxides such as titanium silicon dioxide which has been renowned as most promising electrode material for corrosion inhibition. The possible interactions between PANI and titanium silicon oxide and morphological characteristics of the synthesized nanocomposite were investigated by FTIR, XRD, TEM and SEM. The anticorrosion performance of different PANI/titanium silicon oxide (PTS) nanocomposites coatings were investigated in 0.5 M HNO3 medium by the potentiodynamic technique and electrochemical impedance spectroscopy (EIS) on mild steel. The most pronounced improvement in anticorrosion property of PANI was obtained by using 15% PTS composition of synthesized nanocomposite. The performance of this nanocomposite as an anticorrosive material has been investigated through EIS on mild steel.

Electrochemical Investigation of the Hydrogen Evolution Reaction on Electrodeposited Films of Cr(OH)3 and Cr2O3 in Mild Alkaline Solutions

The hydrogen evolution reaction (HER) from water reduction is the main cathodic reaction in the sodium chlorate process. The reaction typically takes place on electrodes covered with a Cr(III) oxide-like film formed in situ by reduction of sodium dichromate in order to avoid reduction of hypochlorite and thereby increase the selectivity for the HER. However, the chemical structure of the Cr(III) oxide-like film is still under debate. In the present work, the kinetics of the HER were studied using titanium electrodes covered with electrodeposited Cr(OH)3 or Cr2O3, which were characterized by means of scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. A clear difference in the morphology of the deposited surfaces was obtained, and the structure could be revealed with Raman spectroscopy. The kinetics for the HER were investigated using potentiodynamic and potentiostatic techniques. The results show that the first electron transfer is rate limiting and that the activity decreases in the order Cr2O3@Ti > bare Ti > Cr(OH)3@Ti. The low activity obtained for Cr(OH)3@Ti is discussed in terms of the involvement of structural water in the HER and the slow ligand exchange rate for water in Cr(III) complexes, while the high activity obtained for Cr2O3@Ti is rationalized by a surface area effect in combination with reduction of surface water and water in solution.Graphical ᅟ

Surface and corrosion properties of modified passive layer on 304 stainless steel as bipolar plates for PEMFCs

In this study, the relation between surface chemistry and corrosion properties of modified 304 stainless steels (304SS) was investigated. 304SS samples were submitted to plasma nitriding performed at two different temperatures: 420 °C (low) and 520 °C (high). Then, a thermo reactive deposition (TRD) was used in a mixture of ferro niobium, alumina and ammonium chloride. Finally, a pickling treatment was performed to access high corrosion resistant surfaces. Surface treated samples, both before and after pickling, were investigated by using Scanning Electron Microscopy (SEM) and Potentiodynamic (PD) techniques. X-ray Photoelectron Spectroscopy (XPS) was performed for the analysis of the surface layers of the samples after pickling.The surface layers were mostly comprised of iron and chromium oxides and hydroxides. XPS results proved the presence of a surface layer mostly constituted by iron oxides and oxyhydroxides for both the treated samples that resulted more homogenous for the sample nitrided at low temperature. Chromium was detected by XPS in the predominant form of oxide on the surface of the sample nitrided at low temperature.

On-site H2O2 electrogeneration at a CoS2-based air-diffusion cathode for the electrochemical degradation of organic pollutants

This work reports, for the first time, the manufacture and use of an air-diffusion cathode containing CoS2 nanoparticles to enhance the H2O2 electrogeneration. Hydrothermal synthesis allowed the formation of crystalline CoS2 with pyrite structure, either unsupported or supported on carbon nanotubes. Both kinds of catalysts were characterized by X-ray diffraction and FE-SEM combined with energy dispersive X-ray analysis. The use of carbon nanotubes as support led to a remarkable enhancement of the CoS2 stability, as deduced from cyclic voltammetry analysis. The electrochemical activity of the CoS2-based materials towards the oxygen reduction reaction (ORR) in acidic medium was examined by potentiodynamic techniques using a rotating disk electrode. Both catalysts showed activity towards the ORR, being predominant the two-electron pathway to form H2O2 as main product. A novel CoS2-on-carbon nanotubes catalyzed air-diffusion cathode, as well as an uncatalyzed one made for comparison, was manufactured to electrogenerate H2O2 under galvanostatic conditions in an undivided two-electrode cell. A concentration of 56.9mM was found with the former cathode at 100mAcm−2, much >32.0mM found with the uncatalyzed cathode. This informs about the high performance of the CoS2 nanoparticles to promote the two-electron ORR. Finally, the treatment of aqueous solutions of the anaesthetic tetracaine at pH3.0 and 100mAcm−2 by electro-oxidation and photoelectro-Fenton processes demonstrated the viability of the manufactured CoS2-based cathode for water treatment.

Nitrogen-Doped Three-Dimensional Graphene-Supported Palladium Nanocomposites: High-Performance Cathode Catalysts for Oxygen Reduction Reactions

This study reports an effective strategy for fabricating three-dimensional nitrogen-doped graphene supports for palladium nanoparticles (Pd–N/3D-GNS) and studying the electrochemical activity of the synthesized nanocomposites toward oxygen electroreduction in alkaline media as well as implementing the nanocomposite as cathode catalysts in anion exchange membrane fuel cells (AEMFC). It was demonstrated that by embedding and etching an amorphous sacrificial silica template into the reduced graphene matrix, the as-prepared nanocomposites pyrolyzed into hierarchically porous 3D-nanosheets composed of interconnected nitrogen-doped graphene nanostacks, which was confirmed using transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Palladium nanoparticles were then deposited on the N/3D-GNS supports using a surfactant-free technique and characterized using various surface analysis and potentiodynamic techniques. By analyzing the linear sweep voltammograms obtained ...

The effect of pH, fluoride and tribocorrosion on the surface properties of dental archwires

Nickel-titanium and stainless steel are the most commonly used alloys for orthodontic treatments. Even though both are known to be resistant to corrosion, there are circumstances that can lead to undesired situations, like localized types of corrosion attack, wear during sliding of an archwire though brackets and breakdowns due to iatrogenic causes. The aim of this research was to analyse the influence of environmental effects on the corrosion and tribocorrosion properties of NiTi and stainless steel dental alloys. The effects of pH and fluorides on the electrochemical properties were studied using the cyclic potentiodynamic technique. The migration of ions from the alloy into saliva during exposure to saliva with and without the presence of wear was analysed using ICP-MS analyses. Auger spectroscopy was used to study the formation of a passive oxide layer on different dental alloys. It was found that lowering the pH preferentially affects the corrosion susceptibility of NiTi alloys, whereas stainless steel dental archwires are prone to local types of corrosion. The NiTi alloy is not affected by smaller increases of fluoride ions up to 0.024M, while at 0.076M (simulating the use of toothpaste) the properties are affected. A leaching test during wear-assisted corrosion showed that the concentrations of Ni ions released into the saliva exceeded the limit value of 0.5μg/cm2/week. The oxide films on the NiTi and stainless steel alloys after the tribocorrosion experiment were thicker than those exposed to saliva only.

Electrochemical analysis of the ASTM F75 alloy at different pH values and temperatures

The electrochemical behavior of ASTM F75 alloy was analyzed in a sodium chloride solution at pH values of 5, 7, and 9 and temperatures of 37 and 42 °C. The tests were performed in samples corresponding to two different regions of a hip prosthesis. Polarization curves showed that as pH increased the passivity range decreased. However, according to the complementary potentiodynamic–potentiostatic–potentiodynamic technique performed, the increase in the anodic current density was due to a change in the chromium oxidation state from Cr+3 to Cr+6 to form CrO4−2, and not to localized corrosion. On the other hand, neither the microstructure nor the temperature had influence on the electrochemical response of ASTM F75. The electrochemical impedance spectroscopy test showed that as pH increased, the passive film became more compact and thicker. However, its resistance decreased and the electrical double layer became more disordered, promoting diffusion processes of charged species. These results are in agreement with those obtained in the polarization curves, which showed an increase in the dissolution of the passive film, caused by the change in the chromium oxidation state, as pH increased.

Rare earth chloride and nitrate salts as individual and mixed inhibitors for aluminium alloy 7075-T6 in chloride solution

ABSTRACTThe aim of the study was to investigate various rare earth salts as corrosion inhibitors of aluminium alloy 7075-T6. Rare earth salts, CeCl3, LaCl3, Ce(NO3)3 and La(NO3)3, were studied, first as individual inhibitors in the concentration range between 0.001 and 0.05 M. Second, the inhibitory effect of mixtures of chloride or nitrate salts was studied at an overall inhibitor concentration of 0.01 M. The corrosion properties of AA7075-T6 in the absence and presence of individual and mixed rare earth salts were investigated using electrochemical potentiodynamic technique in 0.1 M NaCl. The topography, morphology and composition of the inhibited surfaces were recorded. The highest inhibitory effectiveness was exhibited by CeCl3, followed by mixtures of CeCl3 and LaCl3. During immersion for 12 h the corrosion protection remained high. Nitrate rare earth salts showed less protection, both as individual or as mixed inhibitors. Deposits containing both cerium and lanthanum were formed primarily on Cu-based intermetallics.

An effective and novel pore sealing agent to enhance the corrosion resistance performance of Al coating in artificial ocean water

A new technique was accepted to fill the porosity of Al coating applied by arc thermal spray process to enhance corrosion resistance performance in artificial ocean water. The porosity is the inherent property of arc thermal spray coating process. In this study, applied coating was treated with different concentrations of ammonium phosphate mono basic (NH4H2PO4: AP) solution thereafter dried at room temperature and kept in humidity chamber for 7d to deposit uniform film. The corrosion resistance of Al coating and treated samples have been evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic techniques with exposure periods in artificial ocean water. Electrochemical techniques, X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and field emission-scanning electron microscopy (FE-SEM) indicated that phosphate ion would have been retarding corrosion of Al coating effectively. The formation of AHP (Ammonium Aluminum Hydrogen Phosphate Hydrate: NH4)3Al5H6(PO4)8.18H2O) on Al coating surface after treatment with AP is nano sized, crystalline and uniformly deposited but after exposure them in artificial ocean water, they form AHPH (Aluminum hydroxide phosphate hydrate Al3(PO4)2(OH)3(H2O)5) that is very protective, adherent, uniform and plate like morphology of corrosion products. The AHPH is sparingly soluble and adherent to surface and imparted improved corrosion resistance.

The Study of Pt and Pd based Anode Catalysis for Formic Acid Fuel Cell

Detailed investigation of HCOOH electro-oxidation started about five decades ago, with the advent of modern potentiodynamic techniques, driven initially by the purpose of elucidating some of the most interesting and challenging electrode kinetic problems. Many pioneering works that withstood the test of time and the continuous sophistication of surface electrochemistry techniques were published in the 1960s. Stimulated results were obtained, such as: (i) phenomenological interpretation of anodic polarization curves (e.g., Determination of Tafel parameters), HCOOH oxidation on Pd and Pt catalysts; (ii) discovery of the catalytic effect with respect to Pt and Pd for HCCOH oxidation; (iii) investigation of the potential dependent adsorption of HCOOH on Pt and Pd catalysts which are accompanied by a dual pathway mechanism and (iv) formic acid concentration, temperature effects and crossover of nafion membrane.

Investigation on corrosion protection mechanism of polyaniline nanoparticles doped with phosphoric acid by scanning Kelvin probe and other electrochemical methods

Abstract In this research corrosion protection mechanism of Polyaniline nanoparticles (PANs) doped with phosphoric acid dispersed in the Epoxy–Novolac polymer was investigated. Scanning and transmission electron microscopy proved PANs nanometer size and uniform dispersion in Epoxy. Conductivity, EIS, Potentiodynamic, OCP measurements and Scanning Kelvin Probe technique were used to study the protection mechanism of PANs. It was proved that PANs in the coating stabilize the potential of metal in passive state via formation of protective oxide layer and passivation of pinholes on the carbon steel. Coefficient of variation of surface Volta potentials was suggested as an index for investigation on corrosion uniformity under the coatings in presence of PANs.

Corrosion Inhibition of a Gas Sparged Copper Cylinder in a Solution of NaCl and Na2S by Using 4-Amino-4H-1,2,4-triazole as Corrosion Inhibitor


 Most of previous investigations for corrosion inhibition of copper using triazole derivatives were carried out in stagnant conditions and mainly in presence either NaCl or Na2S. The main aim of this work is to investigate the performance of one of triazole derivatives namely, 4-Amino-4H-1,2,4-triazole (AHT) on improving the corrosion resistance of gas sparged copper parts in a solution comprised of NaCl and Na2S with different propotions. The potentiodynamic technique was used for investigating the effect of different variables on the corrosion rate of gas sparged copper such as gas velocity, initial S-2 concentration, gas sparged copper cylinder diameter, and initial AHT inhibitor concentration. The results show that the %improvement in corrosion resistance depends mainly on two main parameters, gas flow rate and amount of AHT inhibitor added. For lower gas velocities 0.07 cm/s the %improvement ranges from 6 to 22%, while for higher gas rate 0.35 cm/s it ranges from 2 to 7% depending on the amount of inhibitor added. The activation energy of the reaction was found to increase by approximately 20% by addition of the inhibitor up to 10ppm. 

Electrochemical preparation and characterization of a new conducting copolymer of 2,7-carbazole and 3-octylthiophene

In the present work, the synthesis and study of the electrochemical behavior of 2,7-bis(3-octylthiophene-2-yl)-N-methylcarbazole are reported. The electropolymerization of this monomer was achieved by potentiodynamic cyclic voltammetry and potentiostatic techniques. Voltammograms show that two different conducting deposits are formed on Pt for oxidation at 1.0 and 0.8 V. The nature of the deposits depends on the applied potential and the scan rate. Both deposits exhibit n- and p-doping/undoping processes that are thermodynamically reversible and kinetically partially reversible. The same behavior was determined on fluorine-doped tin oxide. The nucleation and growth mechanism (NGM) of the electropolymerization were investigated using a potentiostatic technique (i–t). Two mechanisms were obtained, and the deconvolution of the current–time transient for the low-potential data fitted with a theoretical model suggesting that at short times, an instantaneous nucleation with a two-dimensional growth contribution prevails, followed by a three-dimensional progressive nucleation with a transfer charge diffusion. Finally, at longer times, a three-dimensional progressive nucleation with a diffusion-controlled growth contribution becomes important. The morphology predicted from these NGMs fully correlates with that determined by scanning electron microscopy.

Complex evaluation and development of electrolytic tin refining in acidic chloride media for processing tin-based scrap from lead-free soldering

Different ways of investigation were applied to address the main difficulties of electrolytically refining the tin-based lead-free soldering waste materials in chloride solutions. The characteristics of electrorefining and the phenomena of electrocrystallisation have been targeted by examining the electrode processes with different copper and silver concentrations in the anodes. Galvanostatic experiments were carried out using a specially developed system detecting the changes in the electrode masses continually, complemented by the recording of the electrode potentials. In order to clarify the main cathode and anode processes, further investigations were carried out by the potentiodynamic technique. Galvanostatic results pointed out the causes of current losses and rough deposit structure. Potentiodynamic examinations have demonstrated the strong influence of material transport on the electrode processes. Nevertheless, with a quasi-optimised procedure, cathode tin of higher purity than technical standards could be achieved from the soldering waste material in a conventional cell.

H2SO4수용액에서의 주조용 알루미늄 합금들의 부식거동

The corrosion behavior of aluminum alloys in the <TEX>$H_2SO_4$</TEX> solution was investigated based on potentiodynamic techniques. Electrochemical properties, such as corrosion potential(<TEX>$E_c$</TEX>), passive potential(<TEX>$E_p$</TEX>), corrosion current density(<TEX>$I_c$</TEX>), corrosion rate(mpy), of Al-Mg-Si, Al-Cu-Si and Al-Si alloys were characterized at room temperature. Passive aluminum oxide film, which including <TEX>$Al_2(SO_4)_3$</TEX> and <TEX>$3Al_2O_34SO_38H_2O$</TEX>, were uniformly formed on the surface via the reaction of Al with <TEX>$SO{_3}^{2-}$</TEX> or <TEX>$SO{_4}^{2-}$</TEX> ions in the <TEX>$H_2SO_4$</TEX> solution and the dependence of the corrosion behavior on the alloying element was discussed. The selective leaching of alloy element increased with increasing Cu content in the aluminum alloys.

Evaluation of corrosion resistance properties of N, N′-Dimethyl ethanolamine corrosion inhibitor in saturated Ca(OH)2 solution with different concentrations of chloride ions by electrochemical experiments

Steel rebars attain passivity in concrete environment. Passive film can be destroyed by acidification through carbonation and chloride ions from NaCl in concrete. There are different techniques have been employed to mitigate the corrosion problem of steel rebars embedded in concrete. Among different methods inhibitors are very popular and frequently used. Commercially available N, N′-Dimethyl ethanol amine (DMEA) inhibitor is studied in different concentrations of NaCl in saturated Ca(OH)2 solution. The performance of inhibitor was evaluated by potential time, electrochemical impedance spectroscopy and potentiodynamic techniques. DMEA inhibitor is showing 63–74% efficiency and effectively reduces the corrosion rate.

Investigation of Galvanic Corrosion Behavior of Dual Phase Steel

Dual phase steel has been widely used in the automotive industry to produce lighter weight vehicles to meet stringent safety and fuel economy regulations. One potential concern with dual phase steel is galvanic corrosion when it is exposed to a corrosive environment. In dual phase steel, the dissimilarity in chemical composition and lattice structure could induce different corrosion potentials between the ferrite and martensite phases. As a result, microscopic galvanic couplings could be formed between ferrite grains and their neighboring martensite grains. In this study, the corrosion behaviors of three commercial steel grades: carbon steel, martensitic steel and dual phase steel, are investigated with a variety of electrochemical and surface analytical techniques to understand the mechanism of galvanic corrosion of dual phase steel. The corrosion potential of each steel grade is determined with potentiodynamic technique when the steel is exposed to sodium chloride (NaCl) solution. The study shows that the corrosion potential of dual phase steel is an intermediate between martensitic and carbon steels. In a galvanic coupling of carbon steel/ martensitic steel, carbon steel is found to corrode to protect martensitic steel when exposed to NaCl solution. Examination of dual phase steel after immersion in NaCL solution for an extended period of time indicates the occurrence of galvanic corrosion in the dual phase steel. The corrosion is found to occur primarily in the ferrite phase of dual phase steel.

Effect of phosphoric acid concentration on conductivity of anodic passive film formed on surface of lead–indium alloy

The addition of phosphoric acid into sulfuric acid solution is mentioned to be helpful in the reduction of sulfation after deep discharge of lead-acid battery. The anodic behavior of Pb and Pb–In alloys was studied in pure phosphoric acid and sulfuric acid containing various concentrations of phosphoric. The electrochemical measurements were performed using potentiodynamic, potentiostatic and cyclic voltammetric techniques. The composition and morphology of passive layer formed on the surfaces of Pb and Pb–In alloys were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy analysis (EDX) and scanning electron microscopy (SEM). The potentiodynamic study shows that the passive current density increases with increasing the indium content in the alloy in the examined solutions. The addition of 0.1 mol/L H3PO4 into the electrolyte is more effective to decrease the thickness of passive film on the surface of alloys containing higher indium content (10% and 15%). The XRD, EDX and SEM data reveal that the formation of PbSO4 and PbO on the surface decreases with increasing the indium level in the alloy and is completely prevented at higher indium content (15%) in mixed acid.

Electrochemical behavior and corrosion resistance of electrodeposited nano-particles Zn-Co-Fe alloy

Purpose – The purpose of this study was to compare the electrodeposition behavior and corrosion resistance of ternary and binary alloys. Design/methodology/approach – Potentiodynamic polarization resistance measurement and anodic linear sweep voltammetry techniques were used for the corrosion study. The surface morphology and chemical composition of the deposits were examined using scanning electron microscopy and atomic absorption spectroscopy, respectively. The phase structure was characterized by X-ray diffraction analysis. Electrodeposition behavior was carried out using cyclic voltammetry and galvanostatic techniques. Findings – It was found that the obtained ternary alloy exhibited better corrosion resistance and a more-preferred surface appearance compared to the binary alloys that were electrodeposited under similar conditions. Research limitations/implications – The ternary alloy showed better anticorrosion properties compared to binary deposits that were electroplated successfully from the plating baths. The Zn-Co-Fe alloy could be used advantageously in industry because the ternary alloy exhibits the collective properties of the binary alloys in one alloy via the electrodeposition of Zn-Ni-Co alloy. Social implications – Increasing the corrosion resistance implies to social economic increases. Originality/value – To date, the electrodeposition of Zn-Co-Fe alloy was studied in only a small number of articles. It was found that the presence of Co or Fe could provide a useful coating on the steel that would reduce its susceptibility to corrosion attack.