Hierarchical coating architecture for cement composites: Coupling mechanical reinforcement with corrosion mitigation in marine environments

The increasingly complex service environment demands higher durability and functionality for concrete coatings; however, balancing mechanical strength and corrosion resistance remains challenging. This study presents a bottom-up approach to fabricating a coating with a dual protective structure on concrete surfaces. Inspired by nacre's layered architecture, biomimetic mineralization is employed to in situ construct a robust, dense, and multilayered ordered calcium carbonate framework. This framework serves as a solid substrate for developing a stable superhydrophobic outer surface with lotus-leaf-like papillary structures. The internal structure emulates the “brick-mud” layered composite of natural pearls, using alternating hard mineral and tough organic phases for stress dispersion and energy dissipation. The external structure integrates micro-nano rough features with low-surface-energy materials to create superhydrophobicity, effectively reducing adhesion and penetration of corrosive liquids. The coating exhibits robust mechanical properties (Hardness: 1.49 ± 0.02 GPa, Young's modulus: 42.17 ± 0.48 GPa) and superhydrophobicity (CA: 152°, SA: 6°). It significantly reduces capillary water absorption by 92.76 % and shows excellent performance in wear resistance, UV aging, and corrosion protection. This biomimetic composite coating provides dual protection via internal structural reinforcement and external hydrophobic barriers, enabling it to protect concrete structures in harsh service environments, such as marine infrastructure, industrial facilities, and coastal structures, while endowing them with excellent mechanical properties and corrosion resistance simultaneously. This study provides a promising approach for fabricating multifunctional coatings with desired properties and structures, and offers an effective strategy for protecting concrete infrastructure in marine environments.