Effect of chloride ions on the corrosion behaviour of steel in 0.1 M citrate

The corrosion behaviour of steel was studied in aerated near neutral citrate solutions without and with various concentrations of NaCl. The potentiodynamic anodic polarization curve in 0.1 M citrate solution exhibits four anodic peaks A1, A2, A3 and A4 prior to the oxygen evolution reaction. Addition of Cl⁻ ions to the solution enhances the four peaks currents, specially A3, which is followed by pitting corrosion. The negative going scans of the cyclic voltammograms show two anodic reactivation peaks A5 and A6 and one cathodic plateau P1. A diffusion controlled process in the potential range of A1, A2 and P1 was detected by RDE experiments. The potentiostatic current time transients, at different concentrations of NaCl and applied potentials E_a > A3, were studied. The pit nucleation rate (t_i⁻¹) is found to increase with increasing the concentration of NaCl and the applied anodic potential. The impedance spectra exhibit four different behaviours depending on the potential range used. They were fitted with a single time constant circuit at E_a < −700 mV. However, at −700 mV < E_a < −480 mV, they were fitted with a circuit with two time constants. At E_a > −480 mV, the second semicircle is replaced by negative polarization resistance which is disappeared at E_a > −300 mV. The electrode impedance was found to decrease with the applied potential.     

Electrochemical behaviour of passive films on molybdenum-containing austenitic stainless steels in aqueous solutions

Passivation and its breakdown reactions have been studied on Mo-containing stainless steel specimens using different electrochemical techniques. Mo-containing stainless steel specimens were polarized in both naturally aerated NaCl and Na₂SO₄ solutions of different concentrations at 25 ± 0.2 °C between −1000 and 1500 mV versus saturated calomel electrode (SCE). The results of potentiodynamic polarization showed that i_corr and i_c increases with increasing either Cl⁻ or SO₄²⁻ concentration indicating the decrease in passivity of the formed film. EIS measurements under open circuit conditions confirmed that the passivity of the film decrease with increase in either Cl⁻ or SO₄²⁻ concentration.     

The influence of chloride and sulphate ions on the corrosion behavior of Ti and Ti-6Al-4V alloy in oxalic acid

The electrochemical behavior of pure Ti and Ti-6Al-4V alloy was investigated in oxalic acid solution using various electrochemical techniques, i.e. open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance measurements (EIS) and surface examination via scanning electron microscope (SEM) technique. The influence of concentration and temperature on the electrochemical behavior of TI and its alloy were also studied. The results of polarization measurements showed that corrosion current density (i_corr) increases with increasing either temperature or oxalic acid concentration for both samples. Moreover, the value of i_corr for Ti was found to be lower than that for Ti-6Al-4 V alloy, where the corrosion resistance for titanium was always higher. The effect of additives as SO₄²⁻ and Cl⁻ ions was studied; results indicated that the oxide film resistance (R_ox) value decreases with increasing the concentration of SO₄²⁻ ion. However, for Cl⁻ ion, the value of R_ox decreases with increasing Cl⁻ ion concentration up to 1 mM before it starts to increase at higher concentrations. EIS and polarization results are in good agreement with each other. The obtained results were confirmed by surface examination.     

Streaming effect of single electrolyte mass transfer in nanofiltration: potential application for the selective defluorination of brackish drinking waters

This work deals with electrical properties of nanosurfaces in contact with electrolyte solutions. Single halide ion solutions were studied by streaming potential (SP) measurements and observed retention (R_obs) of the F⁻, Cl⁻, and Br⁻ ions across nanofiltration (NF) membranes. The detailed understanding of an electrolyte solution mass transfer requires an intimate knowledge of the physicochemical interactions occurring between nanoporous materials and electrolyte solutions across the first-generation composite membranes called NF55, NF70 and NF90. These membranes are composed of a polysulfone mesoporous sublayer and a microporous skin layer in polyamide. In order to get a better understanding of these effects, it seems attractive to compare the mass transfer permeation of the monovalent ions F⁻, Cl⁻, and Br⁻ with the electrokinetic characterizations deduced from a properly developed SP apparatus. SP measurements is a very simple method to show the intrinsinc charges on membrane pore walls. The membrane's electrical properties are studied with SP design modeling pH, ionic strength and kind of electrolyte solutions. We have observed that the isoelectric point (IEP) of the membrane materials is both dependent on the ionic strength and on the kind of electrolyte solution. The IEP in the presence of KCl is 4.4 at 0.0001 mol/L and 5.8 at 0.001 mol/L, showing an increasing adsorption of the cation K⁺ by increasing its solution concentration. For a fixed concentration, the effect of the electrolyte solution has shown that a higher adsorption of Ca⁺⁺ occurs in comparison to K⁺ and Na⁺. But the adsorption of these electrolyte solutions is essentially reversible as observed under dilution conditions. Furthermore SP measurements were used for the first time to characterize the transmembrane pressure ranges where a convective and/or a diffusional mass transfer occurs. Such an approach was developed to correlate the R_obs of the halide ions F⁻, Cl⁻ and Br⁻ with the kind of mass transfer (diffusional and/or convective) occurring predominantly under transmembrane pressure variations. Thus the NF70 membrane shows at low pressure (under 3 bar) the order of R_obs following the hydrated ionic radius: R_obs.(F⁻)>R_obs.(Cl⁻)>R_obs.(Br⁻). For a higher pressure (> 3 bar) an inversion occurs between Cl⁻ and Br⁻, but F⁻ was not affected. These results open a new prospective area for selective defluorination of brackish drinking waters using NF membranes under low transmembrane pressure.     

AC impedance spectroscopy study of the corrosion behavior of an AZ91 magnesium alloy in 0.1 M sodium sulfate solution

The corrosion behavior of an AZ91 magnesium alloy in 0.1 M sodium sulfate solution at the corrosion potential (E_corr) was investigated using electrochemical impedance spectroscopy (EIS), environmental scanning electron microscopy (ESEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results showed that when the immersion time was less than 18th, general corrosion occurred on the surface and the main corrosion products were hydroxides and sulfates. The film coverage effect was the main mechanism for the corrosion process of AZ91 alloy. At this stage, the matrix had a better corrosion resistance. With the increasing immersion time, pitting occurred on the surface. At this stage, the corrosion process was controlled by three surface state variables: the area fraction θ₁ of the region controlled by the formation of Mg(OH)₂, the area fraction θ₂ of the region controlled by the precipitation of MgAl₂(SO₄)₄·2H₂O, and the metastable Mg⁺ concentration C_m.     

Initiation and propagation of pitting and crevice corrosion of hydrogen-containing passive films on X70 micro-alloyed steel

Hydrogen promoted initiation and propagation of pitting and crevice corrosion of X70 micro-alloyed steel were characterized by potential dynamic measurements, the scanning reference electrode technique (SRET) and electrochemical impedance spectra (EIS). At open circuit potential, in situ SRET results show that hydrogen accelerates the nucleation and propagation of pitting of X70 steel. The pitting potential E_p of X70 steel gradually decreases with an increase of chloride ion concentration in NaHCO₃ solution. Pre-charged hydrogen does not have a significant effect on the pitting potential E_p and open circuit potential E_corr of the steel in 0.5 M NaHCO₃ solution. However, a synergistic effect of hydrogen and Cl⁻ on the anodic dissolution and pitting potential of X70 steel is observed in 0.5 M NaHCO₃ solution containing chloride ions. When crevices are present in X70 steel, hydrogen accelerates the initiation and progress of crevice corrosion. The mechanisms by which hydrogen promotes the initiation and propagation of pitting and crevice corrosion are proposed and discussed.     

Highly salicylate-selective membrane electrode based on a new thiomacrocyclic Schiff base complex of binuclear copper(II) as neutral carrier

New binuclear metallic complexes of thiomacrocyclic Schiff base, 3,9,13,19 -tetraphenyl-6,16-dithione-1,11-dithio-4,5,7,8,14,15,17,18-octaazacycloeicosa-3,8,13,18-tetraene binuclear metal(II) [M(II)₂-TDDOCT] (M = Cu, Co, Ni), were synthesized and their anion response characteristics were investigated. The performances of the electrodes are considerably influenced by the nature of the central metals. The Cu(II) complex-based electrode exhibited a good selectivity to salicylate anion with an anti-Hofmeister selectivity pattern: Sal⁻ > ClO₄⁻ > SCN⁻ > I⁻ > Benzoate > B_r⁻ > Acetate > F⁻ > SO₃²⁻ > NO₂⁻ > Cl⁻ > NO₃⁻ > SO₄²⁻ > H₂PO₄⁻. The electrode had an excellent linear response to Sal⁻ from 9.0 × 10^− 7 to 1.0 × 10^− 1 M with a slope of − 59.3 mV per decade,a detection limit of 5.0 × 10^− 7 M, and a fast response time within 15 s over the entire concentration series in phosphate buffer solutions of pH 5.0 at 25 °C. Spectroscopic techniques and the influence of lipophilic charged additives on the electrode behavior were used to investigate the response mechanism to Sal⁻. The electrode can be applied to the direct determination of salicylate in human urine and pharmaceutical samples and the results obtained are in accord with the results from a standard method.     

Anodic polarization behavior of low-carbon steel in concentrated sodium hydroxide and sodium nitrate solutions

High-level radioactive wastes, primarily consisting of concentrated sodium hydroxide (NaOH) and sodium nitrate (NaNO₃) solutions, are stored in large underground storage tanks made of low-carbon steel. The anodic polarization behavior of low-carbon steel in concentrated solutions of 10 M NaOH and various concentrations of NaNO₃ (0.01-2.0 M) was determined in order to predict the caustic stress corrosion cracking (CSCC) susceptibility of the tanks. The active-passive transition peak exhibited during anodic polarization of low-carbon steel in 10 M NaOH, typically associated with CSCC, at −0.25 and −0.75 V_SCE, is still present at the lower and higher concentrations of nitrate. However, there is a mid-range of nitrate concentrations (0.5-1 M) within which the peak is suppressed by the strongly oxidizing nitrate in the presence of oxygen, a cathodic depolarizer. Temperature also affects the magnitude of this mid-range of nitrate concentrations where CSCC is seen to be electrochemically prevented. The data suggest that the oxygen solubility at the relatively low temperatures tested (<95 °C) controls the preference of the cathodic reaction, i.e. oxygen reduction versus nitrate reduction. When oxygen reduction is the preferred cathodic reaction, E_corr is driven more noble than the active-passive transition peak.     

Study of the mechanism of additives on copper dissolution in monoethanolamine-complexed cupric ion solution

The dissolution of copper in monoethanolamine (MEA)-complexed cupric ion solution containing different additives was studied. Bridging ligands, such as F^–, Cl^–, Br^–, I^–, SCN^–, and oxidizers, including S₂O₈ ^2–, Cr₂O₇ ^2–, MnO₄ ^– were added to this nonammoniacal etching solution to increase the copper dissolution rate. Potentiodynamic methods were employed to elucidate the dissolution mechanism and the corrosion potential (E _corr) was found to shift from 10 to 90 mV as opposed to that of the original solution (0.045 M cupric sulfate and 0.225 M MEA) for bridging ligands. In contrast, some conventional oxidizers were also added in the etchant and the E _corr did not shift obviously. Therefore, we proposed that copper dissolution proceeds through an inner-sphere pathway in solution containing bridging ligands. The electron is transferred from the copper surface into the cupric species through the ligands, which greatly influences the copper dissolution rate. The order of effectiveness of these ligands is SCN^– > I^– > Br^– > Cl^– > F^–, which is related to their polarizability.     

Role of Cl in breakdown of Cu-Ag alloys passivity in aqueous carbonate solutions

The electrochemical behaviour of two Cu-Ag alloys was studied in 0.1 M Na₂CO₃ solution containing different concentrations of Cl⁻ ions using linear polarization and current/time transients under the effect of different variables of Cl⁻ ions concentration, scan rate and applied anodic potentials. In Cl⁻ free solutions, the anodic voltammogram consists of two potential regions I and II. The potential region I exhibits three anodic peaks A₁, A₂ and A₃ that correspond to the formation of Cu₂O, Cu(OH)₂ and CuO, respectively. The potential region II exhibited four anodic peaks A₄, A₅, A₆ and A₇ due to the formation of AgO⁻, Ag₂O, Ag₂CO₃ and Ag₂O₂. In the presence of Cl⁻ ions, the anodic voltammograms depends considerable on the concentration of Cl⁻ ions. Increasing the amounts of Cl⁻ ions up the 0.02 M (alloy I) or 0.006 M (alloy II) the heights of all the anodic peaks were decreased and their peak potentials were shifted to less negative values. The existence of pitting was confirmed by SEM micrograph. The pitting potential E_pit was shifted towards more active potential values as the concentration of Cl⁻ ions in the solution was increased. When the scan rate is high, initiation of the pitting can be noticed only at more positive potentials, corresponding to a sufficiently short pit incubation time. The potentiostatic current/time transients show that the incubation time decreases with increasing the applied anodic potential and the Cl⁻ ion concentration and the pitting corrosion can be described in terms of instantaneous three-dimensional growth under diffusion control.     

Evaluation and origins of the difference between double-layer capacitance behaviour at Au-metal and oxidized Au surfaces

In studies of processes at oxidized compared with unoxidized electrode surfaces by transient methods corrections for double-layer charging are usually required and have often been made by extrapolation of double-layer capacitance (C_dl) data for the metallic surface, e.g. at Au or Pt, into the potential region of oxide-film formation. Voltammetry and impedance spectroscopy provide direct information on C_dl values determined at unoxidized, i.e. metallic, Au surfaces compared with those of anodic oxide films generated potentiostatically to various extents that are stable in time, and characterized by reductive linear-sweep voltammetry. C_dl is derived from constant-phase element (CPE) values and the CPE parameter, ?, which is near unity for most conditions. At oxidized Au surfaces C_dl depends on potential for various extents of oxide formation; it increases from 15 (±1) μF cm⁻² at 1.75 V (RHE) to 25 (±1) μF cm⁻² at 1.45 V (RHE) and is independent of added Cl⁻ or Br⁻ for concentrations 0-10⁻³ M of both anions, while, at unoxidized Au electrodes in the absence of halide anions, C_dl has a maximum value of 60 (±2) μF cm⁻² at 0.80 V (RHE) and is now dependent on concentration of added Cl⁻ or Br⁻ ion. These major differences of C_dl for the oxidized and unoxidized Au surfaces indicate that double-layer charging corrections cannot be made simply by extrapolation of C_dl data for unoxidized Au metal surfaces into the potential region for oxide formation.     

Kinetics and mechanism of oxygen reduction at hydrous oxide film-covered platinum electrode in alkaline solution

This study uses rotating ring-disk electrode (RRDE) and linear sweep voltammetry (LSV) to characterize oxygen reduction kinetics in alkaline solution on platinum electrodes with various thickness of hydrous oxide (oxyhydroxy) film. Oxyhydroxy films are created on Pt electrodes by pretreatment in 1.0 mol dm⁻³ KOH at a constant voltage. The pretreatment voltage ranges from −1.2 to 1.0 V and is increased stepwise before each new experimental run to produce seven discreet films. LSV plots show oxyhydroxy film thickness strongly inhibits oxygen reduction and is inversely proportional to RRDE oxygen reduction current I_D for LSV voltages E_D from −0.1 to −0.46 V, but this trend reverses at E_D more negative than −0.46 V so that the worst-performing electrode becomes the best. However, this improvement disappears at around −0.8 V, suggesting this change involves a negatively charged ion, possibly embedded into the metal in the top few atomic layers either interstitially or substitutionally. The 1.0 V-pretreated electrode in the E_D range from −0.46 to −0.9 V of highest oxygen reduction current also exhibits the lowest hydrogen peroxide production, with zero H₂O₂ produced at −0.6 V, indicating the brief presence of the oxyhydroxy film on the Pt surface has strong lingering effects. The post-oxyhydroxy Pt surface is very different than the native Pt for oxygen reduction pathway and efficiency. Reaction order with respect to oxygen is close to 1. The rate constants of the direct O₂ to H₂O electroreduction reaction are increased with decreasing the potential from −0.2 to −0.6 V, but the O₂ to H₂O₂ electroreduction is contrary to this expectation. The rate constants of H₂O₂ decomposition on the oxyhydroxy film-covered Pt electrode are near constant around 1 × 10⁻⁴ cm s⁻¹ at E_D > −0.5 V.     

Electrochemical behaviour of titanium in H2SO4-MnSO4 electrolytes

The corrosion of titanium in H₂SO₄ electrolytes (0.001-1.0 M) at temperatures from ambient to 98 °C has been investigated using steady-state polarization measurements. Four distinct regions of behaviour were identified, namely active corrosion, the active-passive transition, passive region and the dielectric breakdown region. The active corrosion and active-passive transition were characterized by anodic peak current (i_m) and voltage (E_m), which in turn were found to vary with the experimental conditions, i.e., d(log?(im))/dpH=−0.8±0.1 and dE_m/dpH which was −71 mV at 98 °C, −58 mV at 80 °C and −28 mV at 60 °C. The activation energy for titanium corrosion, determined from temperature studies, was found to be 67.7 kJ mol⁻¹ in 0.1 M H₂SO₄ and 56.7 kJ mol⁻¹ in 1.0 M H₂SO₄. The dielectric breakdown voltage (E_d) of the passive TiO₂ film was found to vary depending on how much TiO₂ was present. The inclusion of Mn²⁺ into the H₂SO₄ electrolyte, as is done during the commercial electrodeposition of manganese dioxide, resulted in a decrease in titanium corrosion current, possibly due to Mn²⁺ adsorption limiting electrolyte access to the substrate.     

Changes on iron electrode surface during hydrogen permeation in borate buffer solution

Hydrogen interaction with oxide films grown on iron electrodes at open circuit potential (E_oc) and in the passive region (+0.30 V_ECS) was studied by chronopotentiometry, chronoamperometry and electrochemical impedance spectroscopy techniques. The results were obtained in deaerated 0.3 mol L⁻¹ H₃BO₃ + 0.075 mol L⁻¹ Na₂B₄O₇ (BB, pH 8.4) solution before, during and after hydrogen permeation. The iron oxide film modification was also investigated by means of in situ X-ray absorption near-edge spectroscopy (XANES) and scanning electrochemical microscopy (SECM) before and during hydrogen permeation. The main conclusion was that the passive film is reduced during the hydrogen diffusion. The hydrogen permeation stabilizes the iron surface at a potential close to the thermodynamic water stability line where hydrogen evolution can occur. The stationary condition required for the determination of the permeation parameters cannot be easily attained on iron surface during hydrogen permeation. Moreover, additional attention must be paid when obtaining the transport parameters using the classical permeation cell.     

Perovskite-type La2−xSrxNiO4 (0 ≤ x ≤ 1) as active anode materials for methanol oxidation in alkaline solutions

Perovskite-type ternary oxides with molecular formulae, La_2−xSr_xNiO₄ (0 ≤ x ≤ 1), were prepared by a modified citric acid sol-gel route at 600 °C for their possible use in a direct methanol fuel cell (DMFC). The study was conducted by cyclic voltammetry, chronoamperometry, impedance and anodic Tafel polarization techniques. The results showed that the electrocatalytic activity of the base oxide (x = 0) in 1 M KOH plus 1 M CH₃OH at 25 °C increases with x, the observed current densities being 23.6, 47.3, 43.2 and 50.9 mA cm⁻² at a scan rate of 10 mV s⁻¹ and E = 0.6 V versus Hg/HgO for oxides with x = 0, 0.25, 0.5 and 1.0, respectively. All the four perovskite anodes used in this study did not indicate any poisoning by the methanol oxidation intermediates/products. The methanol electro-oxidation reaction followed a Tafel slope of ∼2 × 2.303RT/3F (=40 mV decade⁻¹) on each oxide catalyst, regardless of Sr content.     

Influence of halide ions on the adsorption of diphenylamine on iron in 0.5 M H2SO4 solutions

Halide ions are found to enhance the inhibition performance of amines due to enhanced adsorption of amines by the adsorbed halide ions on the metal surface. In this work, the synergistic action of halide ions on the corrosion inhibition of iron in 0.5 M H₂SO₄ by diphenylamine has been found out by electrochemical impedance and polarization methods. Analysis of impedance data has been made with equivalent circuit with constant phase angle element for calculation of double layer capacitance values. Experiments have been carried out in the concentration range of 100-1000 ppm of diphenylamine in the presence of 0.5-1.0 × 10⁻³ M of halide ions. Diphenylamine is found to be a cathodic inhibitor and the inhibition efficiency of about 65% is obtained at 1000 ppm. The anodic and cathodic Tafel slopes in the presence of diphenylamine alone and with halide ions are 65 ± 5 and 105 ± 5 mV, respectively. Diphenylamine inhibits corrosion by adsorption and the surface coverage values are increased considerably in the presence of halide ions. In the presence of iodide ions, the inhibition efficiency of diphenylamine at 100 ppm is increased to more than 90%. In the case of other halide ions, the inhibition efficiency of diphenylamine in increased to 80% at 1000 ppm. The order of synergism of halide ions is I⁻ ? Br⁻ > Cl⁻. The highest synergistic effect of iodide ions is due to chemisorption with metal surface due to its larger size and ease of polarizability.     

Inhibitory effect of tungstate, molybdate and nitrite ions on the carbon steel pitting corrosion in alkaline formation water containing Cl ion

The pitting corrosion of carbon steel in carbonate-formation water solution in the presence of chloride ions and the effect of addition WO₄²⁻, MoO₄²⁻ and NO₂⁻ anions on the pitting corrosion were studied using cyclic voltammetry and potentiostatic current-time measurements and complemented by scan electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) investigations. Cyclic voltammograms of carbon steel in the presence of chloride ions in carbonate-formation water solution show one anodic peak, corresponding to the formation green rust carbonate and the two cathodic peaks. As the addition of Cl⁻ ions concentration increases, the anodic peak current density increases and pitting potential E_pit shifts to more negative potential. It is shown that the rate of pit initiation () decreases and the pitting potential E_pit moves to more positive direction upon the addition of inorganic anions. It was found that pitting inhibition of carbon steel increases in the sequence: (WO₄)²⁻ > (MoO₄)²⁻ > (NO₂)⁻.     

Influence of cerium on passivity behavior of wrought AZ91 alloy

In this paper, more focus had been put on the passivity behavior of wrought AZ91 alloy with 1.5 mass% Ce. The passive current density of wrought AZ91 alloy increased with addition of Ce and the passive film became unstable. Structures and compositions of the passive films formed on wrought AZ91 alloy without and with Ce in 0.01 M NaOH aqueous solution were analyzed by potentiostatic polarization, potentiostatic-galvanostatic (P-G) transient technique and X-ray photoelectron spectroscopy (XPS). The results showed that Ce only accumulated in the inner layer of passive film in the form of CeO₂. Further analysis revealed that there were two main effects of Ce on the passive process of wrought AZ91 alloy: first, the existence of CeO₂ in inner layer of passive film made mass transport through the passive film follow tangent hyperbolic (T) impedance instead of Warburg impedance (W); second, donor concentration (N_d) of the passive film increased by a factor 10 when 1.5 mass% Ce existed in wrought AZ91 alloy, which led to the higher passivity current density.     

Study on the electrochemical behaviour of the anticancer herbal drug emodin

The electrochemical behaviour of the anticancer herbal drug emodin was investigated by cyclic voltammetry (CV) at glassy carbon electrode. In 0.05 M NH₃-NH₄Cl (50% ethanol, pH 7.2) buffer solution, a pair of quasi-reversible redox peaks at potentials of Ep1 = −0.688 V and Ep2 = −0.628 V and one irreversible anodic peak, which was a typical anodic peak of emodin, at Ep3 = −0.235 V appeared at a scan rate of 100 mV/s. The irreversible anodic peak currents are linearly related to the emodin concentrations in a range from 8.9 × 10⁻⁸ M to 7.8 × 10⁻⁶ M with a pre-concentration time of 80 s under −0.620 V. Using the established method without pretreatment and pre-separation, emodin in herbal drug was determined with satisfactory results. Moreover, the electrode process dynamics parameters were also investigated by electrochemical techniques.     

Electrocatalytic reduction of bromate ion using a polyaniline-modified electrode: An efficient and green technology for the removal of BrO3 in aqueous solutions

The electrocatalytic reduction of bromate ion (BrO₃⁻) was investigated in a three-electrode system using polyaniline (PANI) as the electrode material. Bromate ion reduction and Br⁻ removal were observed during electrochemical treatment because of the catalytic and doping capabilities of the PANI film. BrO₃⁻ removal efficiency in the 0.10 mol L⁻¹ Na₂SO₄ supporting electrolyte achieved 99% at pH 7 in 25 min, with no bromide ion detected in the solution. Optimal removal was found in pH range 6-7, and the pH of the solution had a significant impact on bromate reduction. A reduction mechanism was also discussed by analyzing the cyclic voltammograms of the reduction process and X-ray photoelectron spectra of the main elements (N 1s and Br 3d) on the PANI surface. We propose that during the electrocatalytic reduction process, bromate is reduced to bromide because of the loss of electrons from the nitrogen atoms on the PANI chains. The doping of the resultant Br⁻ ions in the PANI film has an important role in avoiding further oxidation of Br⁻ to BrO₃⁻. The used PANI film can be regenerated by de-doping the Br⁻ ions with a 0.5 mol L⁻¹ H₂SO₄ solution. Thus the process can be considered efficient and green.