Study of metal corrosion in a tropical marine atmosphere rich in H2S resulting from the decomposition of sargassum algae : application to copper, zinc and steel ; Impact de la biodégradation des sargasses sur la corrosion atmosphérique des alliages métalliques utilisés comme matériaux de connectiques : Rôles des gaz liés à la dégradation et étude d'une solution de protection biosourcée caribéenne

This work investigates the influence of gases from biodegradation of Sargassum algae, in particular hydrogen sulphide (H2S), on the atmospheric corrosion of steel, copper and zinc. It has been shown that the presence of hydrogen sulphide from the biodegradation of stranded algae in the areas impacted by large arrivals plays an important role in the premature degradation/corrosion of common metals (e.g. connectors). This factor is added to other factors characteristic of a tropical marine atmosphere that is already very aggressive towards metallic materials (high TOW, sea spray loaded with Cl -ions, constant and high temperatures throughout the year). In this study, many parameters were considered (H2S and sea salt concentration, distance from the shore, etc.) to characterise the corrosiveness of the sites. In the first part of this work, the study of atmospheric corrosion of copper showed that corrosion rates obtained by gravimetry are very high in the impacted areas. This study was supported by surface analyses (SEM/EDX and XRD) revealing very degraded corrosion surfaces, altered by the presence of H2S in the atmosphere. The electrochemical studies (via electrochemical impedance spectroscopy and linear polarisation techniques) have made it possible to propose an electrochemical model of the corrosion phenomena occurring on the surface of metals. The second and third parts of this work deal respectively with the study of atmospheric corrosion, under these particularly aggressive conditions, of zinc and steel. ; Ce travail étudie l’influence des gaz issus de la biodégradation des sargasses, en particulier le sulfure d’hydrogène (H2S), sur la corrosion atmosphérique de l’acier, du cuivre et du zinc. Il a été montré que la présence de sulfure d’hydrogène issu de la biodégradation des algues échouées dans les zones impactées par les arrivages conséquents joue un rôle important dans la dégradation/corrosion prématurée des métaux usuels (connectique notamment). Ce facteur s’ajoute à d’autres facteurs caractéristiques ...