Vincent VIVIER, is full time researcher and research director at the LISE laboratory Sorbonne Université. He focuses his research on electrochemical impedance spectroscopy (EIS) and on the development of local electrochemical techniques (scanning electrochemical microscopy - SECM, local electrochemical impedance spectroscopy - LEIS) and the development of coupled techniques (SECM and electrochemical quartz crystal microbalance, SECM and electrolyte resistance) in order to sense the local reactivity of various types of interfaces, including corrosion and material degradation. Among recent and currently running projects many are related with the development of new electrochemical characterization methods for energy conversion devices and the degradation of battery materials.
Laboratoire Interfaces et Systèmes Electrochimiques Sorbonne Université - Paris
The electrochemical study of metastable events occurring during pitting corrosion remains complex because many individual processes may develop simultaneously on the metal surface. To overcome this difficulty, different techniques have been developed in order to generate a single pit and to study its evolution. In this presentation, it will be shown different ways of generating a single pit, including the use of a flow micro-device allowing a single pit to be initiated and then propagated, and we will take advantage of such a device in order to revisit the different parameters involved in the pitting process. In a first step, the pitting corrosion of iron will be studied with a specific setup combining quartz-crystal microbalance and scanning electrochemical microscopy. Then the evolution of the pit geometry for stainless steel will be presented, showing a diffusion-limited mechanism for the pit depth and an Ohmic control at the pit aperture. In a third step, different experiments performed, as a function of chloride concentration to investigate the pit stability will be discussed. From statistical analysis performed on identical experiments, the construction of a zone diagrams showing the stability of the pit as a function of the chloride concentration and the pit dimensions will be discussed. In a last step, an experimental setup modified in order to measure the pitting current of a single pit simultaneously with the Raman spectrum will be presented. It will be shown that in situ spectroscopic measurements allow identifying species inside the pit. It was thus possible to link the sulphate concentration (and thus the pH variation) inside the pit to the current as a function of time. To conclude, the advantages and the limitations of local electrochemical approaches for the study of pitting corrosion will be sum-up.