**6. Conclusions**

The thorough characterization of the corrosion product layers provided important information that led to a better understanding of the mechanisms of marine corrosion of carbon steel permanently immersed in natural seawater. Important facts must be pointed out:


outer surface of this layer as long as the magnetite particles remain interconnected and connected to the steel surface.


**Author Contributions:** Conceptualization, all authors; methodology, all authors; validation, all authors; formal analysis, all authors; investigation, all authors; writing—original draft preparation, P.R.; writing—review and editing, all authors; visualization, P.R., M.J.; supervision, A.-M.G., P.R.; project administration, A.-M.G., P.R.; funding acquisition, A.-M.G., P.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** The various studies synthesized here were funded by: the Technological Research Institute Jules Verne of Nantes (France) through the ADUSCOR research program; the European Regional Development Fund (ERDF) and the CDA of La Rochelle through the DYPOMAR research project; the seaports (GPM) of La Rochelle, Nantes-Saint-Nazaire, Marseille, and Le Havre.

**Conflicts of Interest:** The authors declare no conflict of interest.
