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Theses

Couplage galvanique Cu-Al en milieu confiné

Abstract : Aluminium-copper alloys, such as 2024 alloy (4 % Cu) are widely used in the aircraft industry for their low density combined with very good mechanical properties. Nevertheless, these alloys are very sensitive to corrosion. In the case of the alloy 2024, the presence of copper rich particles, embedded in a matrix of aluminum leads to localized attack as a result of galvanic corrosion. In bulk aerated electrolyte with neutral pH, the galvanic coupling between the two metals occurs as expected: aluminium dissolution is the anodic reaction and oxygen reduction is the cathodic reaction at the surface of copper. Nevertheless in 2024 alloys, the formation of a crevice at the Al/Cu interface, with copper redeposition in the vicinity of the interface has often been observed, but up to now has not been clearly explained. Thus the aim of this work is to highlight the mechanism of copper dissolution and deposition at the aluminium matrix and to see the influence of confinement on this behaviour. The thin layer cell assembly used in this work mimics a crevice through confining an electrolyte layer (thickness lower than a few hundreds of micrometers) between two parallel plans containing respectively a pure copper and a pure aluminium surface The galvanic current and potential were followed as a function of time, of distance between the two metals, and for surface ratios of respectively 10 and 0.1 between copper and aluminium. After replacing the upper electrode by an insulating wall, the behaviour of the copper electrode could be followed in presence of Al3+ ions in the thin layer. Finally the mechanism of galvanic coupling was discussed taking into account the modification of pH and the radial potential distribution at the surface of the metals within the thin electrolyte layer. Keywords: Al-
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https://tel.archives-ouvertes.fr/tel-00831650
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Submitted on : Friday, June 7, 2013 - 2:21:21 PM
Last modification on : Sunday, June 26, 2022 - 9:39:34 AM
Long-term archiving on: : Tuesday, April 4, 2017 - 6:42:21 PM

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  • HAL Id : tel-00831650, version 1

Citation

Sameer Joma. Couplage galvanique Cu-Al en milieu confiné. Chimie. Université Pierre et Marie Curie - Paris VI, 2013. Français. ⟨tel-00831650⟩

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