Foreword

The 17th Topical Meeting of the International Society of Electrochemistry was held in the Palais du Grand Large in Saint-Malo, France from 31 May to 3 June 2015. The theme of the meeting was “Multiscale Analysis of Electrochemical Systems”, and involved ISE Division 4 (Electrochemical Materials Science) and ISE Division 7 (Physical Electrochemistry). About 180 scientists from 35 countries participated in the meeting

Corrosion inhibition of 2024 aluminium alloy by sodium decanoate

The present study concerns the corrosion protection of the aluminium alloy (AA) 2024 by sodium decanoate (a long-carbon-chain carboxylate). This compound-type is known to form hydrophobic films on the metal surface. The characterization of the inhibition mechanisms was studied for different experimental conditions (pH, NaCl concentrations) by using electrochemical techniques. Special attention was paid to the action of the carboxylate on the intermetallic particles by performing local electrochemical impedance measurements on a model system (Al/Cu couple). The decanoate afforded high protection to the AA2024 both by preventing chloride ion attack of the oxide layer and by limiting galvanic coupling between the intermetallic particles and the surrounding matrix. A passivation effect of the compound was also shown

Local Electrochemical Measurements in Bipolar Experiments for Corrosion Studies

In this work, the local potential and local current were measured with paired Ag/AgCl reference microelectrodes during the corrosion of a 304L stainless-steel (304L SS) sample in bipolar experiments. During a single experiment, it was possible to investigate both the anodic and cathodic domains corresponding to the corrosion of the stainless steel. From these local measurements in non-contact mode, the current/potential curve was obtained, revealing the different reactivities of the 304L SS sample, over a large potential range. The polarisation curve was similar to that usually obtained in a classical three-electrode configuration

EIS 2007: The 7th international symposium on electrochemical impedance spectroscopy

EIS 2007: The 7th international symposium on electrochemical impedance spectroscop

Galvanic coupling between copper and aluminium in a thin-layer cell

The Al/Cu coupling was investigated in a thin-layer cell formed by a large Cu electrode and an Al microelectrode embedded in an insulator placed above the Cu electrode. By using a scanning electrochemical microscope (SECM) the thickness of the thin layer was perfectly controlledwith a precision in the micrometer range. A copper deposit on an electrochemical quartz crystal microbalance (EQCM) was also used as SECM substrate to quantify the copper dissolution rate. It was shown that such an experimental set-up allows to mimic the galvanic corrosion of intermetallic particles embedded in the aluminium matrix of the 2XXX series aluminium alloys. The combination of the SECM and the EQCM permitted the evaluation of the corrosion rate of copper at the corrosion potential of the 2024 Al alloy, whereas cyclic voltammetry performed on the SECM tip indicated the enrichment in Cu2+ ions in the thin electrolyte layer

Influence of flow on the corrosion inhibition of carbon steel by fatty amines in association with phosphonocarboxylic acid salts

This work was carried out to study the inhibition mechanism of a carbon steel in a 200 mg l−1 NaCl solution by a non-toxic multi-component inhibitor used for water treatment in cooling circuits. The inhibitive formulation was composed of 50 mg l−1 fatty amines associated with 200 mg l−1 phosphonocarboxylic acid salts. Steady-state current–voltage curves, obtained with a rotating disc electrode, revealed that the properties of the protective layer were dependent on the electrode rotation rate and on the immersion time. The cathodic process of oxygen reduction was not modified in the presence of the inhibitive mixture. As expected, the current densities increased when the rotation rate was increased. In the anodic range, original behaviour was observed: the current densities decreased when the electrode rotation rate increased. The morphology and the chemical composition of the inhibitive layers allowed the electrochemical results to be explained. Two distinct surface areas were visualised on the metal surface and the ratio between the two zones was dependent on the flow conditions. This behaviour was attributed to a mechanical effect linked to centrifugal force. XPS analysis revealed that the formation of a chelate between the phosphonocarboxylic acid salt molecules and the iron oxide/hydroxide was enhanced by the increase of the electrode rotation rate

Local and global electrochemical impedances applied to the corrosion behaviour of an AZ91 magnesium alloy

The electrochemical behaviour of an AZ91 magnesium alloy was investigated in a low aggressive medium by means of local and global electrochemical impedance measurements. The results were compared to those obtained on a pure magnesium sample. It was possible to show the individual contribution of each phase constituting the alloy, and it was observed that the corrosion mechanism of the two phases was the same, controlled by the Mg dissolution. However, local impedance diagrams clearly indicated that the kinetics dissolution of the b-phase was slower than that of the a-phase, which was in good agreement with SEM observations

An electrochemical and surface analytical study of the formation of nanoporous oxides on niobium

In the present paper, the anodization of Nb in mixed sulphate + fluoride electrolytes resulting in the formation of a nanoporous oxide film has been studied. Chronoamperometry and electrochemical impedance spectroscopy have been employed to characterise in situ the kinetics of the oxidation process. In addition, the evolution of the layer structure and morphology has been followed by ex situ scanning electron microscopy. Particularly, local electrochemical impedance spectroscopy has been used to discern between the mesoscopic 2D and 3D distributions of time constants at the electrode surface. The similarity between local and global impedance spectra during anodic oxidation of Nb demonstrates the presence of an inherent 3D distribution of the high-frequency time constant, which is interpreted as in-depth variation of the steady state conductivity of the passive film. The experimental and calculational results are discussed in relation to the micro- and nanoscopic structure of the formed oxide

Synergistic effect between 8-hydroxyquinoline and benzotriazole for the corrosion protection of 2024 aluminium alloy: A local electrochemical impedance approach

This work is devoted to the corrosion inhibition of the 2024 aluminium alloy (AA2024) in neutral aqueous solution by 8-hydroxyquinoline (8-HQ) and benzotriazole (BTA). First, current-voltage curves and global electrochemical impedance measurements confirmed that 8-HQ and BTA are two effective corrosion inhibitors for AA2024. Mixing the two compounds led to a synergistic effect for the corrosion protection of the alloy. From the impedance data analysis, it was shown that 8-HQ acted mainly on the aluminium matrix with an additional action of the BTA on the intermetallic particles. Then, to analyse the role of the inhibitors on the galvanic coupling between the aluminium matrix and the particles, local electrochemical impedance measurements were performed on a model system (Al/Cu couple). It was shown that in the presence of 8-HQ or BTA alone, the galvanic coupling between copper and aluminium was little reduced while in the presence of both compounds together it was strongly limited. The local impedance results confirmed the specific inhibition of the 8-HQ and of the BTA on Al and Cu respectively

Localized approach to galvanic coupling in an aluminum–magnesium system

The corrosion behavior of a pure aluminum/pure magnesium couple in a weakly conductive sodium sulfate solution was investigated. Potential and current distributions on the surface of the model couple at the beginning of immersion were obtained by solving the Laplace equation using a finite element method algorithm. Magnesium acted as the anode of the system while oxygen and water were reduced on aluminum. Calculations predicted a large current peak at the Al/Mg interface related to a local increase in both Mg dissolution and oxygen and water reduction on aluminum, leading to a local pH increase. Optical and scanning electron microscope observations confirmed the strong dissolution of magnesium concomitantly with depassivation of aluminum at the Al/Mg interface. Local electrochemical impedance spectroscopy showed the detrimental effects of the galvanic coupling both on aluminum and magnesium