<p>This study presents a comprehensive evaluation of the anticorrosive performance of several direct-to-metal (DTM) coating systems, including a conventional polyurethane (PU) coating, a fully modified organic–inorganic hybrid (Fully OIH) coating, and a partially modified OIH coating (Partially OIH). The coatings were evaluated using water uptake and water contact angle measurements, electrochemical impedance spectroscopy (EIS), salt spray testing, pull-off tests, and mechanical properties (elasticity and plasticity) determined by nanoindentation. The results show that, despite its superior barrier properties, the conventional PU coating, when examined under active corrosion conditions typically occurring near damaged areas, exhibits inferior anticorrosive performance compared to the OIH coatings. This finding indicates that corrosion propagation is primarily driven by coating delamination, highlighting the critical importance of maintaining adhesion after corrosion onset (i.e., wet adhesion) for effective long-term protection. Both OIH coatings demonstrated superior anticorrosive performance due to enhanced wet adhesion resulting from covalent bonding with the substrate. The outstanding anticorrosive performance of the partially OIH coating, despite its inferior barrier properties, was attributed to its higher degree of plasticity, which enhances adhesion by allowing the coating to better accommodate stresses generated by voluminous corrosion products beneath the film.</p>