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RESEARCH PRODUCT

Contribution to the modeling of microstructural corrosion on aluminium alloys : definition of a methodology to study the bimetallic corrosion phenomena

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The initiation and the propagation of aluminum alloys microstructural corrosion is mainly based on the bimetallic corrosion phenomenon. This type of corrosion is caused by galvanic coupling at a local scale between the different phases contained in the alloy. The description of the localized corrosion phenomenon has been largely studied. Their complexity can explain why they are so difficult to predict by the way of numerical tools and why the works that have been done on this subject are so scarce. The present thesis brings a new contribution to this field by suggesting a methodology based on the complementary use of local electrochemical techniques and the finite element simulation of bimetallic corrosion. From an experimental point of view, the capillary electrochemical microcell has been used to get electrochemical kinetic data that are specific to a millimetric bimetallic model system, composed of an electrode of 1199 and an electrode of α-Al4%Cu solid solution. These kinetic data were then used as boundary conditions for the modeling of coupling. S. V. E. T. (Scanning Vibrating Electrode Technique) measurements enable the validation of the numerically obtained current distributions. The use of a model system allowed us to modify several parameters used for simulation, and particularly the type of boundary conditions and the way to take into account the influence of pH on the extent of the anodic phase dissolution. The more satisfying conditions have then been applied to a more realistic system composed of an intermetallic particle, with a cathodic behavior, embedded in the matrix of the concerned aluminum alloy, which has an anodic role.