Behaviour of sodium silicate and sodium phosphate (tribasic) as corrosion inhibitors for iron

The effectiveness of sodium silicate (Na₂SiO₃) and trisodium phosphate (Na₃PO₄) as corrosion inhibitors for iron in 0.1 m NaClO₄, in both aerated and deaerated solutions has been investigated. Both sodium silicate and trisodium phosphate are effective inhibitors in unbuffered solutions as a result of inhibiting the rate of the anodic iron dissolution reaction. However, the inhibition of the corrosion rate in the (final) pH range 9.6–11.6 is entirely due to the change in pH which the addition of Na₂SiO₃ and Na₃PO₄ to unbuffered solutions causes, and not to the presence of silicate/phosphate species. Where the final pH was in the range 5–7 addition of I mm sodium silicate to acidified aerated unbuffered solutions caused slight inhibition of the iron dissolution reaction when compared with a solution of the same pH. Lower concentrations of Na₂SiO₃ at the same final pH did not cause inhibition. Silicic acid has an approximate solubility of 1 mm and it is likely that the inhibitive behaviour in this pH range is due to the precipitation of H₂SiO₃ at the electrode surface. An aerated phosphate buffer of pH 7.0 inhibited both the anodic and cathodic reactions when compared with a 0.1 m sodium perchlorate solution at the same pH. This was due to the presence of phosphate species at the electrode surface. In carbonate and acetate buffers neither Na₂SiO₃ nor Na₃PO₄ caused corrosion inhibition.     

A comprehensive model for predicting CO2 corrosion rate in oil and gas production and transportation systems

A comprehensive carbon dioxide (CO₂) corrosion model was developed to predict steel corrosion rate in oil and gas production and transportation systems. Validated with significant amount of experimental data, this model covers the following three scenarios: (1) deaerated CO₂ corrosion, (2) aerated CO₂ corrosion, and (3) CO₂ corrosion with cathodic protection. This paper is focused on summarizing the uniqueness of this model and the links of the above three scenarios. A flow chart is provided to show a straightforward procedure for solving the model equations. Model results are presented and discussed.     

Inhibitive effect of 1-[(2-hydroxyethyl) amino]-2-(salicylideneamino)ethane toward corrosion of carbon steel in CO2-saturated 3.0% NaCl solution

The performance of 1-[(2-hydroxyethyl) amino]-2-(salicylideneamino)ethane (HAS) as a corrosion inhibitor for carbon steel in CO₂-saturated 3.0% NaCl solution under aerated and deaerated conditions was studied using weight loss and potentiodynamic polarization methods at different temperatures. The results obtained show that in aerated environment, HAS acts as an effective corrosion inhibitor for carbon steel in CO₂-saturated brine solution and accelerate corrosion under deaerated condition. Inhibition efficiency (IE%) increased with increase in HAS concentration but decreased with increase in temperature. Corrosion inhibition action was via the adsorption of HAS on the metal’s surface which follows the Langmuir adsorption isotherm model. Polarization curves indicate that HAS functions as a mixed-type inhibitor.     

“Deactivation of copper electrode” in electrochemical reduction of CO2

Metallic Cu electrode can electrochemically reduce CO₂ to CH₄, C₂H₄ and alcohols with high yields as revealed by the present authors. Many workers reported that formation of CH₄ and C₂H₄ rapidly diminishes during electrolysis of CO₂ reduction. This paper shows that such deactivation of Cu electrode is reproduced with electrolyte solutions prepared from reagents used by these workers. Deactivated Cu electrodes recovered the electrocatalytic activity for CO₂ reduction by anodic polarization at −0.05 V versus she in agreement with the previous reports. Features of the deactivation depend greatly on the individual chemical reagents. Purification of the electrolyte solution by preelectrolysis with a Pt black electrode effectively prevents the deactivation of Cu electrode. Anode stripping voltammetry of Cu electrodes, which were deactivated during electrolysis of CO₂ reduction, showed anodic oxidation peaks at ca. −0.1 or −0.56 V versus she. The severer the deactivation of the Cu electrode was, the higher electric charge of the anodic peak was observed. It is presumed that some impurity heavy metal, originally contained in the electrolyte, is deposited on the Cu electrode during the CO₂ reduction, poisoning the electrocatalytic activity. On the basis of the potential of the anodic peaks, Fe²⁺ and Zn²⁺ are assumed to be the major contaminants, which cause the deactivation of the Cu electrode. Deliberate addition of Fe²⁺ or Zn²⁺ to the electrolyte solutions purified by preelectrolysis exactly reproduced the deactivation of a Cu electrode in CO₂ reduction. The amount of the deposited Fe or Zn on the electrode was below the monolayer coverage. Electrothermal atomic absorption spectrometry (etaas) showed that Fe originally contained in the electrolyte solution is effectively removed by the preelectrolysis of the solution. Mechanistic difference is discussed between Fe and Zn in the deterioration of the electrocatalytic property of Cu electrode in the CO₂ reduction. The concentration of the impurity substances originally contained in the chemical reagents as Fe or Zn is estimated to be far below the standard of the impurity levels guaranteed by the manufacturers. Presence of trimethylamine in the electrolyte solution also severely poisons a Cu electrode in the CO₂ reduction. It was concluded that the deactivation of Cu electrode in CO₂ reduction is not caused by adsorption of the products or the intermediates produced in CO₂ reduction.     

Silver-coated ion exchange membrane electrode applied to electrochemical reduction of carbon dioxide

Silver-coated ion exchange membrane electrodes (solid polymer electrolyte, SPE) were prepared by electroless deposition of silver onto ion exchange membranes. The SPE electrodes were used for carbon dioxide (CO₂) reduction with 0.2 M K₂SO₄ as the electrolyte with a platinum plate (Pt) for the counterelectrode. In an SPE electrode system prepared from a cation exchange membrane (CEM), the surface of the SPE was partly ruptured during CO₂ reduction, and the reaction was rapidly suppressed. SPE electrodes made of an anion exchange membrane (SPE/AEM) sustained reduction of CO₂ to CO for more than 2 h, whereas, the electrode potential shifted negatively during the electrolysis. The reaction is controlled by the diffusion of CO₂ through the metal layer of the SPE electrode at high current density. Ultrasonic radiation, applied to the preparation of SPE/AEM, was effective to improve the electrode properties, enhancing the electrolysis current of CO₂ reduction. Observation by a scanning electron microscope (SEM) showed that the electrode metal layer became more porous by the ultrasonic radiation treatment. The partial current density of CO₂ reduction by SPE/AEM amounted to 60 mA cm⁻², i.e. three times the upper limit of the conventional electrolysis by a plate electrode. Application of SPE device may contribute to an advancement of CO₂ fixation at ambient temperature and pressure.     

Metastable and stable pitting events on Al induced by chlorate and perchlorate anions—Polarization, XPS and SEM studies

The metastable and stable pitting events of Al were studied in 0.075 M deaerated acidic NaClO₃ and NaClO₄ solutions (pH 3) using potentiodynamic anodic polarization and potentiostatic measurements, complemented with SEM and XPS examinations of the electrode surface. Metastable pits (appeared here as oscillations in current in the nA range) form at potentials close to the pitting potential (E_pit). SEM examinations of the electrode surface showed that the current oscillations resulted in observable pits on sample surface. The repassivated metastable pitting sites are prone to become preferential sites for following metastable pits to nucleate, resulting in accumulated corrosion damages on the surface. Results showed that Cl⁻ ions produced in solution via the reduction of ClO₃⁻ and ClO₄⁻ anions at sufficiently negative cathodic potentials as well as their decomposition at high anodic potentials. Chloride production induced via the reduction of perchlorates is much slower than induced by chlorates. XPS examinations of the electrode surface showed that the amount of ClO₄⁻ and Cl⁻ anions detected on the electrode surface increases with both cathodic and anodic polarizations (even above E_pit). Experimental results revealed that addition of Cl⁻ ions to the ClO₄⁻ solution accelerates pitting corrosion, indicating that these anions cooperate together in passivity breakdown and initiation of pitting. The role of ClO₃⁻ and ClO₄⁻ ions, despite their large size, in pitting process is also discussed here. A point defect model (PDM) is employed to explain passivity breakdown induced by pitting corrosion as a result of the aggressive attack of Cl⁻ ions.     

Electrochemical formation of green rusts in deaerated seawater-like solutions

Carbon steel electrodes were polarised at a potential ∼150 mV higher than the open circuit potential, in a deaerated seawater-like electrolyte (0.5 mol dm⁻³ NaCl, 0.03 mol dm⁻³ Na₂SO₄, 0.003 mol dm⁻³ NaHCO₃). X-ray diffraction and μ-Raman analysis demonstrated that a layer mainly composed of GR(SO₄²⁻) had grown on the steel surface. GR(SO₄²⁻) was accompanied by traces of GR(CO₃²⁻). Similar experiments performed in a solution composed of 0.3 mol dm⁻³ of Na₂SO₄ and 0.03 mol dm⁻³ of NaHCO₃ led to the same result. The nature of the GR forming on steel is thus mainly linked to the sulphate to carbonate concentration ratio. Finally, carbon steel coupons immersed for 11 years in the harbour of La Rochelle (Atlantic coast) were removed from seawater for analysis. The inner part of the rust layer proved to be mainly composed of magnetite, GR(SO₄²⁻) and iron sulphide FeS. This definitively confirms that GR(SO₄²⁻), as Fe₃O₄ and FeS, can form from steel in O₂-depleted environments.     

Electrochemical behavior of an anion-exchanger modified electrode prepared by sol-gel processing of an organofunctional silicon alkoxide

Sol-gel films prepared from quaternary amine functionalized silicon alkoxide precursor on electrode surfaces have been investigated as anion-exchange and permselective coatings for electroanalytical investigations. These modified electrodes were evaluated with Fe(CN)₆³⁻ and Ru(bpy)₃²⁺ as the analytes using cyclic voltammetry. At low solution pH, the anionic analyte preconcentrated within the functionalized sol-gel coating and resulted in an improvement in detection limit of about 2 orders of magnitude compared to bare electrodes, but the response for the cationic analyte was suppressed. The modified electrodes are rugged and reproducible and can be regenerated. We have also shown that the anion-exchange and permselective properties of the modified electrodes can be affected by the composition, concentration, and pH of the support electrolyte.     

In Situ Soft X‐ray Microscopy Study of Fe Interconnect Corrosion in Ionic Liquid‐Based Nano‐PEMFC Half‐Cells

This in situ soft X‐ray scanning microscopy electrochemical study of model proton exchange cathodic and anodic nano‐fuel cells is exploring the evolving structure and chemical composition of key cell components represented by Au and Fe electrodes in contact with Nafion‐ionic liquid composite electrolyte containing Pt black catalyst particles. Morphological and chemical changes of the electrodes as well as the chemical state and fate of the Fe species released into the electrolyte are monitored in short circuit and with applied cathodic or anodic polarization. The in situ X‐ray absorption images of the cathodic cell fed with 2.5 × 10^–5 mbar O₂ have revealed corrosion‐induced morphology changes in the Fe electrode, being more pronounced in the vicinity of Pt‐black particles, and deposition of the Fe species released into the electrolyte, onto the intact Au counter electrode upon cathodic polarization. The Fe electrodes of the anodic cell containing NaBH₄ in the electrolyte appear relatively more corrosion resistant. The Fe L₃ absorption spectra taken in different locations within the Fe electrode have shown lateral variations in the relative ratio between Fe²⁺ and Fe^3&4+ oxidation states, whereas the Fe species released into the RTIL electrolyte are only in the high Fe^3&4+ oxidation states.     

Effect of physico-chemical properties of simulated body fluids on the electrochemical behaviour of CoCrMo alloy

The behaviour of the CoCrMo alloy was studied under different experimental conditions of solution pH, chemical composition (phosphate buffer solution with and without addition of bovine serum albumin) and aeration (presence and absence of oxygen in the solution). With this purpose, electrochemical techniques such as open circuit measurements (OCP), potentiodynamic curves, potentiostatic tests and electrochemical impedance spectroscopy (EIS) were employed.The results show that the general corrosion behaviour of CoCrMo alloy depends on the solution pH. Thus, the effect of BSA and the aeration conditions are related to the solution pH. At pH 3 no influence of BSA was observed in deoxygenated solutions which imply that BSA acts over the oxygen reduction reaction in acidic media. On the contrary, a noticeable influence of BSA addition was observed at pH 7.4 (independently on the gas content). Finally, at pH 10, the influence of BSA was only significant in oxygenated solution. It was found that H₂PO₄⁻ favours the formation of passivating compounds which improves the resistance of the CoCrMo alloy to passive dissolution. Therefore, when the concentration of the H₂PO₄⁻ increases (when pH decreases) the polarization resistance of the alloy also increases. On the other hand, the oxygen (aerated conditions) decreases the polarization resistance of the alloy in all the studied conditions.     

Electrochemical impedance spectroscopic investigation of CO2 reduction on polyaniline in methanol

The ac response of polyaniline thin films on platinum electrodes was measured at different dc potentials during the CO₂ reduction in methanol/LiClO₄ electrolyte with a small amount of 0.5 M H₂SO₄. The complex capacitance curves were simulated and the data obtained were used to calculate kinetic parameters, based on the assumption that the thermodynamic potential E₀ is in the region of −0.2-−0.1 V versus saturated calomel electrode (SCE). With E₀=−0.2 V versus SCE and β=0.6, a j₀ value of ca. 10⁻⁴ A cm⁻² was found for the electroreduction of CO₂ on the polyaniline electrode.     

Passivity and passivity breakdown of a zinc electrode in aerated neutral sodium nitrate solutions

The passivation and pitting corrosion behaviour of a zinc electrode in aerated neutral sodium nitrate solutions was investigated by cyclic voltammetry and chronopotentiometry techniques, complemented by ex situ scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) examinations of the electrode surface. Measurements were conducted under different experimental conditions. The potentiodynamic anodic polarization curves do not exhibit active dissolution region due to spontaneous passivation. The passivity is due to the presence of thin film of ZnO on the anode surface. The passive region is followed by pitting corrosion as a result of breakdown of the passive film. SEM images confirmed the existence of pits on the electrode surface. The breakdown potential decreases with an increase in NO₃⁻ concentration and temperature, but increases with increasing potential scan rate. Addition of SO₄²⁻ ions to the nitrate solution accelerates pitting corrosion, while addition of WO₄²⁻ and MoO₄²⁻ ions inhibits pitting corrosion. The chronopotentiometry measurements show that the incubation time for pitting initiation decreases with increasing NO₃⁻ concentration, temperature and applied anodic current density. Addition of SO₄²⁻ ions decreases the rate of passive film growth and the incubation time, while the reverse changes produced by addition of either WO₄²⁻ or MoO₄²⁻ ions.     

Determination of open-circuit potentials at gas/electrode/YSZ boundary versus molten carbonate reference electrode at medium temperatures: I. Potentials of Au and Pt in O2 and H2 + H2O atmospheres

A double gas concentration cell as combination of the cell with the yttria stabilized zirconia (YSZ) electrolyte and the cell with molten Li₂CO₃ + Na₂CO₃ eutectics is proposed as an alternative cell system with a standard reference electrode for measurements of the open-circuit potential (OCP) values of electrodes in oxygen concentration cell with the yttria stabilized zirconia (YSZ) electrolyte. In this double-cell one electrode is common for the two cells and the reference electrode is the standard molten carbonate half-cell with 0.33O₂ + 0.67CO₂ atmosphere. This reference electrode should enable the monitoring of OCP and overpotential values in polarization studies in the three-electrodes configuration. If the possible reaction between the solid YSZ and liquid molten carbonates electrolyte is very slow, the measured values of the open-circuit-voltage (OCV) of this cell may be considered equal to the respective reversible electromotive forces (EMF). Very good resistance of the smooth YSZ products to the corrosion in highly dehydrated Li/Na molten carbonates has been shown in experiments lasting few 1000 h. Hence, the consistency of OCV values with the respective EMF values have been tested at various partial pressures of CO₂ and O₂ in the gas mixtures above the molten carbonate electrolyte and at various partial pressures of O₂ + Ar or H₂ + H₂O gas mixtures at the Au or Pt electrodes/YSZ interface. The results have shown the reliability of the double-cell in determination of the open-circuit potentials (OCP) of gas electrodes at the YSZ surface as measured versus the reference electrode with molten carbonate electrolyte. The consistency of OCP and EMF values has been shown satisfying and enhances to use the proposed double-cell in further investigations of OCP and overpotential values at TPB of electrode/YSZ/mixture of reacting gases. At high differences of O₂ partial pressures on both sides of the YSZ membrane some permeation of this gas through the YSZ membrane has been observed. Probably, this effect has an electrochemical character.     

Corrosion behavior of a positive graphite electrode in vanadium redox flow battery

The graphite plate is easily suffered from corosion because of CO₂ evolution when it acts as the positive electrode for vanadium redox flow battery. The aim is to obtain the initial potential for gas evolution on a positive graphite electrode in 2 mol dm⁻³ H₂SO₄ + 2 mol dm⁻³ VOSO₄ solution. The effects of polarization potential, operating temperature and polarization time on extent of graphite corrosion are investigated by potentiodynamic and potentiostatic techniques. The surface characteristics of graphite electrode before and after corrosion are examined by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The results show that the gas begins to evolve on the graphite electrode when the anodic polarization potential is higher than 1.60 V vs saturated calomel electrode at 20 °C. The CO₂ evolution on the graphite electrode can lead to intergranular corrosion of the graphite when the polarization potential reaches 1.75 V. In addition, the functional groups of COOH and CO introduced on the surface of graphite electrode during corrosion can catalyze the formation of CO₂, therefore, accelerates the corrosion rate of graphite electrode.     

CO2 attraction by specifically adsorbed anions and subsequent accelerated electrochemical reduction

The electrochemical reduction of CO₂ was studied on a copper mesh electrode in aqueous solutions containing 3 M solutions of KCl, KBr and KI as the electrolytes in a two and three phase configurations. Electrochemical experiments were carried out in a laboratory-made, divided H-type cell. The working electrode was a copper mesh, while the counter and reference electrodes were Pt wire and Ag/AgCl electrode, respectively. Results of our work suggest a reaction mechanism for the electrochemical reduction of CO₂ in the two phase configuration where the presence of Cu-X as the catalytic layer facilitates the electron transfer from the electrode to CO₂. Electron-transfer to CO₂ may occur via the X_ad⁻(Br⁻, Cl⁻, I⁻)-C bond, which is formed by the electron flow from the specifically adsorbed halide anion to the vacant orbital of CO₂. The stronger the adsorption of the halide anion to the electrode, the more strongly CO₂ is restrained, resulting in higher CO₂ reduction current. Furthermore, it is suggested that specifically adsorbed halide anions could suppress the adsorption of protons, leading to a higher hydrogen overvoltage. These effects may synergistically mitigate the overpotential necessary for CO₂ reduction, and thus increase the rate of electrochemical CO₂ reduction.     

Removal of arsenic from drinking water by the electrocoagulation using Fe and Al electrodes

A novel technique of electrocoagulation (EC) was attempted in the present investigation to remove arsenic from drinking waters. Experiments were carried out in a batch electrochemical reactor using Al and Fe electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as pH (4–9), current density (2.5–7.5 A m⁻²), initial concentration (75–500 μg L⁻¹) and operating time (0–15 min) were examined. Optimum operating conditions were determined as an operating time of 12.5 min and pH 6.5 for Fe electrode (93.5%) and 15 min and pH 7 for Al electrode (95.7%) at 2.5 A m⁻², respectively. Arsenic removal obtained was highest with Al electrodes. Operating costs at the optimum conditions were calculated as 0.020 € m⁻³ for Fe and 0.017 € m⁻³ for Al electrodes. EC was able to bring down aqueous phase arsenic concentration to less than 10 μg L⁻¹ with Fe and Al electrodes. The adsorption of arsenic over electrochemically produced hydroxides and metal oxide complexes was found to follow pseudo second-order adsorption model. Scanning electron microscopy was also used to analyze surface topography of the solid particles at Fe/Al electrodes during the EC process.     

Polypyrrole and La1−xSrxMnO3 (0≤ x ≤0.4) composite electrodes for electroreduction of oxygen in alkaline medium

Composite G/PPy/PPy(La_1−xSr_xMnO₃)/PPy electrodes made of the perovskite La_1−xSr_xMnO₃ embedded into a polypyrrole (PPy) layer, sandwiched between two pure PPy films, electrodeposited on a graphite support were investigated for electrocatalysis of the oxygen reduction reaction (ORR). PPy and PPy(La_1−xSr_xMnO₃) (0≤ x ≤0.4) successive layers have been obtained on polished and pretreated graphite electrodes following sequential electrodeposition technique. The electrolytes used in the electrodeposition process were Ar saturated 0.1 mol dm⁻³ pyrrole (Py) plus 0.05 mol dm⁻³ K₂SO₄ with and without containing a suspension of 8.33 g L⁻¹ oxide powder. Films were characterized by XRD, SEM, linear sweep voltammetry, cyclic voltammetry (CV) and electrochemical impedance (EI) spectroscopy. Electrochemical investigations were carried out at pH 12 in a 0.5 mol dm⁻³ K₂SO₄ plus 5 mmol dm⁻³ KOH, under both oxygenated and deoxygenated conditions. Results indicate that the porosity of the PPy matrix is considerably enhanced in presence of oxide particles. Sr substitution is found to have little influence on the electrocatalytic activity of the composite electrode towards the ORR. However, the rate of oxygen reduction decreases with decreasing pH of the electrolyte from pH 12 to pH 6. It is noteworthy that in contrast to a non-composite electrode of the same oxide in film form, the composite electrode exhibits much better electrocatalytic activity for the ORR.     

Enhanced high-voltage performance of LiCoO2 cathode by directly coating of the electrode with Li2CO3 via a wet chemical method

Surface modification is an effective method for improving the high-voltage cycling stability of LiCoO₂. In this work, lithium carbonate (Li₂CO₃), the main component of solid electrolyte interphase (SEI) films, is selected as the coating material to modify LiCoO₂ composite electrodes by a wet chemical method, and the effect of the Li₂CO₃ coating time on the electrochemical performance of the LiCoO₂ electrode is investigated. Results show that the Li₂CO₃ coating significantly improves the cycling performances and initial coulombic efficiencies of the LiCoO₂ electrodes in the potential range of 3.0–4.5 V. The electrode with a coating time of 2 min exhibits the best electrochemical performance, in which the capacity retention rate is 90.9% after 100 cycles at 0.2C while the initial coulombic efficiency is 90.04%, whereas the capacity retention rate and initial coulombic efficiency of the uncoated electrode are only 73.11% and 74.66%, respectively. The capacity of the electrode with the 2-min coating reaches 134.3 mA h g^?1 after 500 cycles, while that of the uncoated electrode is only 37.7 mA h g^?1 under the same conditions. The results of cyclic voltammetry, electrochemical impedance spectroscopy, X-ray diffraction, and scanning electron microscopy show that the Li₂CO₃ coating stabilizes the electrode surface and structure to effectively inhibit the increase in electrode polarization.     

Microstructural analysis of the ageing of pseudo-binary (Ti,Zr)Ni intermetallic compounds as negative electrodes of Ni-MH batteries

Ageing of Ti_1.02−xZr_xNi_0.98 (0 ≤ x ≤ 0.48) compounds during the electrochemical cycling in aqueous KOH electrolyte has been investigated. Microstructural and chemical characterisation, mostly conducted by transmission electron microscopy, show that for all electrodes their activation results from calendar KOH corrosion. After activation, Zr substituted compounds attain much higher capacity (∼350 mAh g⁻¹) than the binary TiNi compound (∼150 mAh g⁻¹) but their cycle-life is poor. The mechanism of electrode degradation differs for the binary and the substituted compounds. For TiNi, degradation is due to KOH corrosion whereas, for substituted compounds, it mainly results from the loss of electrical contact due to particle pulverisation. For all electrodes, KOH corrosion produces a double surface layer formed by an inner two-phase (Ni-NiO) nanocrystalline layer and an outer (Ti,Zr)O₂ amorphous layer.     

Anodic, cathodic and cyclic voltammetric deposition of ruthenium oxides from aqueous RuCl3 solutions

Anodic, cathodic and cyclic voltammetric (CV) deposition of ruthenium oxides from aqueous RuCl₃ solutions have been investigated using stationary and rotating disk electrodes (RDE) in this work. The CV deposition behavior was examined using a RDE to differentiate the contribution of current from the reactions of ruthenium ions in the electrolyte and ruthenium oxides already adsorbed on the electrode. The results indicate that the CV growth of ruthenium oxides within the potential range of aqueous electrolyte decomposition is attributed to the anodic oxidation of ruthenium ions in the electrolyte. Cathodic deposition occurs only at potential negative than −0.30 V versus saturated calomel electrode (SCE) when H₂ evolves on the electrodes. Anodic deposition of ruthenium oxides can be obtained effectively in the potential range of ca. 0.9-1.1 V versus SCE, depending on the pH value of the electrolyte. The optimum anodic and cathodic deposition potential for maximum deposition efficiency is 1.0 and −0.9 V versus SCE, respectively, in the electrolyte solution of pH 2.