Le Bureau des Études Doctorales a le plaisir de vous informer que
Madame Cynthia OUEINY,
Doctorante au laboratoire MAPIEM - Matériaux Polymères Interfaces Environnement Marin - EA 4323 rattaché à l’école doctorale 548 « Mer et Sciences », sous la direction de M. François-Xavier PERRIN, co-encadrée par Mme Sophie BERLIOZ, soutiendra publiquement sa thèse en vue de l’obtention du doctorat en Chimie, sur le thème suivant :
Le mardi 16 décembre 2014 à 14h30, à l’Université de Toulon, Campus de la Garde, amphi. du bâtiment M,
The aim of this study was to prepare new protective coatings with self-healing properties and low environmental impact. All investigated systems include n-decyl phosphonic acid (DPA) as an anticorrosion inhibitor. We first showed that DPA was an efficient dispersing agent for the preparation of stable aqueous MWCNT dispersions. From UV-vis spectrometry measurements and TEM analysis, we found that the optimum concentration to homogeneously disperse MWCNT was around 0.18 wt%. For higher concentrations of DPA, no valuable dispersion was obtained because of the depletion-induced aggregation of MWCNT. These DPA-MWCNT dispersions were used to prepare waterborne MWCNT-alkyd protective films with affine dispersion of MWCNT. Then, we prepared polyaniline (PANI) by an interfacial polymerization route using different phosphonic acids (PA) in the aqueous phase. PANI nanofibers were obtained using benzylphosphonic acid while DPA doped PANI nanotubes with an external diameter between 130-240 nm were obtained using DPA. Low carbon steel panels were coated with polyvinyl butyral film loaded with PANI pigments. The corrosion behavior was tested in neutral saline conditions. The best protective performance was obtained with DPA doped PANI. The good protection efficiency was assigned to the smart release of DPA dopants which can form insoluble iron salts to block the damaged site. Finally, MWCNT/ceria/polyaniline ternary composites were prepared by in situ polymerization of aniline on MWCNT/ceria composites. The high amount of ceria nanoparticles (diameter around 10 nm) deposited on oxidized MWCNT was related to the electrostatic interactions between Ce3+ ions and carboxylate groups on MWCNT walls. These composites were immersed in water solutions of different pHs to study the rate of Ce release. The results showed that that cerium species from MWCNT/ceria/PANI composites will be preferentially released in the acidic anodic sites but they can also be released in neutral pH conditions. The corrosion protection performance of PVB films loaded with different MWCNT/Ce and MWCNT/Ce/PANI composites was studied by electrochemical impedance spectroscopy (EIS) and open circuit potential measurements. MWCNT/Ce(IV)/EB resulted in the best corrosion protection performance in neutral saline conditions (immersion/salt spray). A mechanism of protection was proposed based on the EIS and OCP results. PANI was the key element for active and efficient protection performance but Ce NP played a role in the protection certainly through the release and inhibitive properties of Ce(III) and /or Ce(IV) ions.