Corrosion and Biofouling Protection via a Spatial‐Temporal Strategy Enabled by Barrier and Liquid‐Like Interfaces in Ultrathin PECVD Coatings

ABSTRACT In aerosol‐ and condensation‐dominated corrosive environments, ion transport through coatings and surface droplet retention jointly govern corrosion initiation and propagation. However, existing strategies emphasize spatial diffusion barriers while overlooking interfacial liquid regulation. Here, we report a spatial‐temporal protection strategy using an ultrathin coating that integrates alternating organic‐inorganic multilayers with an in situ grafted liquid‐like surface (LLS) via one‐step plasma‐enhanced chemical vapor deposition (PECVD). The multilayer structure provides a tortuous diffusion barrier that retards H 2 O, O 2 , and Cl − transport, while the mobile polysiloxane chains on LLS regulate interfacial microdroplet dynamics by suppressing contact‐line pinning, accelerating droplet detachment, and shortening electrolyte residence time, enabling synergistic anti‐corrosion protection. Interfacial microdroplet activity was quantitatively analyzed during salt‐spray exposure and correlated with corrosion suppression. As a result, the ∼1 µm‐thick 5L+LLS coating exhibits an electrochemical impedance modulus of ∼8.25 × 10 7 Ω·cm 2 in 3.5 wt.% NaCl, stable resistance after long‐term immersion, ∼4% visible corrosion area after 48 h salt‐spray exposure, and ≥98% reduction in the adhesion of E. coli , S. aureus , and Chlorella after 72 h incubation. Enabled by a scalable PECVD process, this work establishes an ultrathin architecture that couples spatial diffusion barriers with temporal interfacial regulation for robust device protection in harsh environments.