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L'action inhibitrice du 2-aminothiophénol (ATP) et du 2-aminophényl disulfure (APDS) sur la corrosion du fer dans HCl 1 M est étudiée par détermination de perte de masse et par analyse des courbes de polarisation potentiodynamique. Ces deux composés (ATP, APDS) réduisent la vitesse de corrosion du fer; cependant, l'APDS présente le meilleur pouvoir inhibiteur. L'effet de la concentration en inhibiteur (ATP, APDS), du temps d'immersion de l'électrode et de la température sur la vitesse de corrosion du fer sont étudiés. L'analyse des courbes de polarisation révèle que ces composés limitent la réaction de dégagement du dihydrogène sur le fer à des potentiels très cathodiques (<−0.60 V vs. ECS). La cinétique de la réaction de dissolution du fer est également diminuée plus en présence d'APDS qu'en présence de l'ATP. Néanmoins, le mécanisme des deux réactions ne semble pas être modifié.Inhibition of iron corrosion in 1 M HCl. Part I. Study of the inhibiting effect of 2-aminothiophenol and of 2-aminophenyl disulfide.The inhibitive action of 2-aminothiophenol (ATP) and 2-aminophenyl disulfide (APDS) on iron corrosion in a 1 M HCl medium was studied by using weight loss determinations and potentiodynamic polarisation curves. Both compounds reduce the iron corrosion rate. APDS presents, however a better inhibitive power. Effect of temperature, inhibitor concentration and electrode immersion time on ATP and APDS behaviour were studied. At very cathodic potential values (less than −0.60 V), polarisation curves show that the two compounds lower hydrogen evolution on iron. ATP and APDS can also reduce the dissolution rate of iron. This effect is more pronounced with APDS. Nevertheless, the two reactions seem to follow the same mechanism as in HCl without any inhibitor.

Electrochemical methods, including polarization experiments and impedance spectroscopy, were used to evaluate the effectiveness of benzotriazole (BTA) in an aqueous solution of polyethylene glycol (PEG) in protecting polished archaeological copper or archaeological copper covered with corrosion products. The adsorption of PEG on the polished copper significantly limited the corrosion current. The presence of benzotriazole enhanced the protection of the polished copper, giving maximum protection at a concentration of 10−2mol l−1of BTA in 20 vol% PEG 400 solution. On the other hand, PEG solutions caused degradation of the corrosion products of the copper. This degradation increased with time. When BTA was added, the corrosion products were preserved and, the higher the BTA concentration, the more the corrosion current decreased. In PEG 400 solution protection of the corrosion products of the copper by BTA improved over time.

A finite element numerical model was set up to calculate the secondary distribution of potential and current density at the surface of a buried tank. The steel gas tank of interest was protected by both coating and two sacrificial anodes (magnesium alloy or zinc). The dispersion of actual soil properties was taken into account by use of three typical soils. The comparison of two dimensional and three-dimensional models shows that the 2D model is obviously both convenient and time saving. The numerical model allows the calculation of the cathodic protection current and of the local potential in every point of the tank. The model intends to compare the relative influence of coating quality, electric conductivity of soil and position, size and type of the sacrificial anodes (magnesium or zinc). Soil conductivity and coating porosity appear as the two most influential parameters. This model justifies the interest of the tank experimental potential and current measurements.List of symbols

A mathematical model of cation intercalation in a layered host lattice is presented. Theoretical potential-time curves for galvanostatic charge-discharge and current-potential curves in linear sweep voltammetry are calculated for the case of cylindrical diffusion including the influence of ion-ion interactions and at the surface of the material. A kinetic analysis of the model behaviour is proposed.

Résumé Les améliorations apportées par l'électrolyte Mg(ClO4)2 + Mg(OH)2 à la conservation et au rendement du couple Zn-MnO2 lors de décharges continues sont contre-balancées par de mauvaises performances aux régimes forts intermittents. Il est montré ici que, ni MnO2, ni la résistance interne de la pile n'en sont responsables, mais que la dépassivation du zinc est insuffisante avec l'ion ClO4- seul. La présence d'ion Cl- améliore de façon sensible cette dépassivation. Un mélange ClO4- + Cl- doit réaliser un bon compromis entre la conservation et les performances en régimes forts intermittents.

Electrosynthesis of peroxodiphosphate ions (P2O84−) was performed in 2m K3PO4, 1m K2HPO4 medium, using a platinum anode. The results showed that under conditions of potentiostatic polarization at constant potential, the reaction rate reaches a maximum value of 125mAcm−2 and a faradaic yield of 30%. From about 1.9V, the reaction kinetics are increasingly inhibited as the potential shifts positively. Rapid scanning potential voltammetry was used to characterize the oxidation state of the electrode surface. This method shows that the growth of α (PtO) and β (PtO2 or PtO3) oxides depend on the applied potential. It also establishes a correlation between the inhibition of P2O84− ion electrosynthesis and the β oxide coating surface. When 2×10−3m KSCN is added to the solution, some oxygen evolution sites are selectively blocked and β oxide occurs at more positive potential values. Consequently, the rate of peroxodiphosphate ion formation and the faradaic efficiency are increased to 380mAcm−2 and 75%, respectively. Under pulsed potential conditions it was possible to reach 1200mAcm−2 for P2O84− ion electrosynthesis with a faradaic yield of 82%.

Résumé Nous avons étudié les propriétés électriques et électrochimiques de réseau de polyuréthanne à base de copolymère triblocs poly(oxyde d'éthylène)/poly(oxyde de propylène) contenant du perchlorate de lithium. La conductivité électrique de ce réseau est supérieure à 10-5 O-1 cm-1 à 20°C. Le domaine de stabilité électrochimique de cet électrolyte polymère est de 4V. Des accumulateurs tout solide RuO2/polyuréthanne chargé de LiClO4/Li ont été réalisés et testés à 60°C. Les rendements expérimentaux sont respectivement de 96.6% à la première décharge, 90% à la première charge et 83% à la deuxième décharge. Ces valeurs sont en accord avec les rendements théoriques correspondant à ces conditions de cyclages.

Résumé La durée de vie en cyclage d'un accumulateur constitue l'un des critères principaux de l'intérêt que l'on peut lui porter. Il est donc très utile de pouvoir l'évaluer rapidement. Nous avons étudié l'évolution, en fonction de son état de charge, de l'impédance d'un générateur au lithium soumis à des cycles décharge-charge dans le but d'analyser, dans un premier temps, les variations des grandeurs caractéristiques de cette impédance en espérant apporter, par cette technique de mesure, des éléments d'évaluation de sa durée de vie.

We develop an electrochemical technique in order to measure the mass transfer across a moving mercuryelectrolyte interface. The method is tested on an electromagnetically excited interface. It allows a continuous time measurement of the mass transfer across an agitated interface between two liquids.

Rest potential measurements and voltammetric scans at different rates (0.01–1 V min-1) have been carried out on aluminium alloys in a tetrahydrofuran (THF) environment. The solvent contained either chloride, perchlorate or trifluoromethane sulfonate ions. For the Al-Mg alloys in chloride environments, the voltammograms observed for low scan rates show electrode passivation with the formation of a magnesium salt layer. For Al-Li alloys, rest potential measurements indicate the selective dissolution of lithium. The maximum dissolution current is sensitive to the lithium content in the alloy and limited by the solubility of lithium chloride. In chloride environments, the passivity breakdown potentialEb and the protective potentialEp have similar values and do not depend on the type of alloy. In contrast, large differences between these potentials are observed in the presence of CF3SO3- ions.

Poly(decaviologen) (DV2+, 2ClO4-) has been prepared and used in the characterization of two redox couples; dication/cation radical ((DV2+, 2 ClO4-)/(DV+•, ClO4-)) and cation radical/decaviologen ((DV+•, ClO4-)/(DVo)) in a polyethylene oxide-LiClO4 medium by linear potential sweep voltammetry. The (DC2+, 2 ClO4-)/(DV+•, ClO4-) couple has been used to determine the transport number of lithium in poly(ethylene oxide)-LiClO4 or LiCF3SO3 complex media.

An electrochemical technique based on concentration cell e.m.f. measurements is used to determine the lithium transference number and diffusion coefficient in poly(ethylene oxide)-lithium salt complexes. Measurements were carried out at 90°C on PEO-LiI, PEO-LiClO4 and PEO-LiCF3SO3 electrolytes. According to the phase diagram of the PEO-lithium salt system these complexes are fully amorphous at 90°C. Accurate determination oftLi+ by the e.m.f. concentration cell method generally requires knowledge of the mean salt activity coefficients. However, this becomes unnecessary when the two electrolyte concentrations differ only slightly. As a first step the mean salt activity coefficient was estimated using a galvanic cell of the lithium/PEO-LiX/MXn/M type withMn+=Ag+ or Pb2+, and X-=I- or CF3SO3-. The resulting lithium transference numbers are 0.34 for the PEO-LiI complex and 0.7 for PEO-LiCF3SO3. Discrepancies between thetLi+ values can be explained by the formation of triplets in the PEO-LiCF3SO3 electrolyte. By recording concentration cell potential versus time and comparing with theoretical curves, the salt lithium diffusion coefficient was obtained.DLiI was found to be around 4×10-8 cm2 s-1 in PEO-LiI and 8×10-8 cm2 s-1 in PEO-LiCF3SO3 at 90°C. These results suggest a liquid-like behaviour for the microscopic transport mechanism.

The electrochemical behavior of high purity aluminium and Al-Li alloy has been investigated in various organic environments. Various lithium- and aluminium-compatible solvents were considered before selecting propylene carbonate (PC) and tetrahydrofuran (THF) with addition of either chloride or perchlorate ions. THF finally proved to be the most suitable solvent for these tests. The aluminium dissolution reaction in a THF environment is fast and reversible. The Al/Al(III) couple can therefore be used as a reference electrode. Aluminium salts can be reduced by lithium, making the Li/Li+ couple unsuitable for the reference electrode. The voltammograms obtained show voltage characteristics (protective potentialEp and breakdown potentialEb) similar to those found in aqueous environments. The voltage variations recorded by potentiometric measurements could be associated with changes in the alloy surface state.

Les performances du couple Zn/MnO2 sont étudiées avec un nouvel électrolyte Mg(ClO4)2-Mg (OH)2. Les principales améliorations apportées, par rapport à la pile Leclanché traditionnelle, concernent la conservation à chaud et la puissance spécifique.