Eliane Sutter

The atmospheric corrosion of copper by hydrogen sulphide in underground conditions

The atmospheric corrosion of copper by hydrogen sulphide has been followed during field tests using different sulphide concentrations, for 77 days, and during exposure to a well-defined synthetic atmosphere in a test chamber. The main components formed at the surface of the samples are copper oxides and sulphide. We show that exposure tests performed for short times in synthetic atmospheres cannot be extrapolated to long time exposure in real conditions, since three successive phases of film growth are observed. The mechanism of film growth is discussed, assuming that cationic diffusion through the cuprous oxides and sulphide is the rate-determining step.

Mechanism of dissolution of a Cu-13Sn alloy in low aggressive conditions

Abstract Corrosion of a synthetic Cu–13Sn alloy with a dendritic structure was investigated in a low aggressive medium (0.01 M Na 2 SO 4 aqueous solution). The corrosion rate was accelerated through anodic polarization of the alloy in a potential range close to the open-circuit potential. The composition of the corrosion layer was followed as a function of the polarization time, using scanning electron microscopy and energy dispersive spectrometry methods. The results clearly showed that bronze corrosion in these experimental conditions proceeds by decuprification. Selective copper dissolution leads to corrosion layers enriched in tin compounds. It was concluded that bronze is partially passivated through the presence of a tin oxide layer, which slows down copper dissolution rate, compared to pure copper.

A Kinetic Model for CO2 Corrosion of Steel in Confined Aqueous Environments

A kinetic model of the physicochemical processes occurring during the corrosion of steel covered by a thin water film exposed to a CO 2 atmosphere is proposed. This model explains theoretically the unusual physicochemical behaviors generally observed in such confined corrosive media: Fe(II) supersaturations, low corrosion rates, high pH values, and their respective dependence on the electrolyte film thickness. More quantitatively, the model predictions agree well with pH and corrosion rate measurements performed in environments similar to the annulus space of flexible pipelines.

Liquid ammoniates: nonaqueous electrolytes for electrochromism

New conductive materials involving Cu + ions are proposed for electrochromic devices. They are liquid ammoniates which can be used from room temperature up to 80°C, and whose conductivity and p(NH3) can be modulated according to requirements. The synthesis does not require strong acids or complexing agents such as halide ions. The principle of operation of the electrochromic material is the reduction of Cu + to Cu at the transparent cathode while Cu + is oxidized to Cu 2 + (thus developing a blue color) at the transparent anode. The bleaching is realized by the reverse reactions.

Corrosion and Hydrogen Permeation in H2S Environments with O2 Contamination, 1: Tests on Pure Iron at High H2S Concentration

Materials selection in the oil and gas industry relies on engineering standards, such as NACE TM0177 and NACE TM0284, which stipulate that oxygen pollution should be avoided during materials testin...

Imaging of a Thin Oxide Film Formation from the Combination of Surface Reflectivity and Electrochemical Methods

Electrochemical methods (cyclic voltammetry (CV), potential steps, and electrochemical impedance spectroscopy) were successfully combined with in situ reflectometry measurements for a detailed analysis of the passive layer evolution as a function of the electrode potential. Interestingly, both EIS and surface reflectivity allowed a film thickness in the nanometer range to be readily determined. In addition, transient analyses of the reflectivity simultaneously recorded with CVs show the formation of both Fe2O3 and Fe3O4 oxides. The image analysis showed that the steel surface reactivity is heterogeneous and presents micrometric islands coated with a thicker oxide layer than the surrounding surface. The in situ combination of these techniques thus offers a powerful analytical description of the interface on a local scale and its transient response to a perturbation.

Influence of Co(II) ions on the electrochemical behavior of n- and p-type GaAs electrodes in boric acid solution

Abstract The kinetics of the reactions at the GaAs–H 3 BO 3 interface at pH 5 is modified by the presence of Co(II) ions in the solution. This effect is shown for oxygen reduction in the dark, at the surface of p-GaAs in aerated solutions: the rate of oxygen reduction is higher for higher Co(II) concentration. Photoanodic dissolution of n-GaAs in deaerated boric acid solution is also affected by Co(II) ions, which enhance the dissolution rate of the semiconductor (SC). It is suggested that a thin coherent oxide film is formed on GaAs in Co(II)-free boric acid solutions. In the presence of Co(II), the breakdown of the oxide allows oxygen adsorption on bare GaAs sites, and the kinetics of oxygen reduction is enhanced at p-GaAs. Breakdown of the oxide layer in the presence of Co(II) ions in the boric acid solution is also obvious during photodissolution of n-GaAs in the absence of oxygen.