Chemical strategies and structural designs of Janus materials for corrosion resistance: Advances & perspectives

Corrosion-induced material degradation in industrial systems necessitates the use of novel and efficient materials with multipurpose qualities for durable protection. The ability of conventional corrosion inhibitors for long-term, aqueous phase protection is negatively impacted by their tendency to be either hydrophilic (easy to solvate in polar electrolytes) or hydrophobic (insoluble). The special chemical, structural, and interfacial features of Janus materials have made them a promising class of effective alternatives with a dual-face asymmetry, meaning that one face is hydrophilic and the other is hydrophobic. This review features the collection of coordination and corrosion inhibition potential of Janus materials, including Janus graphene (G), graphene oxide (GO), Janus silica (Si) nanoparticles, Janus polymers, and their composites. These special materials offer efficient surface covering and protection by adsorbing horizontally at the metal-electrolyte interface. The tailored hydrophilic side of Janus materials faces the metal surface, while the hydrophobic side faces the solution side, deterring water and other corrosive species. Janus materials, especially their composites, can be considered as "complete corrosion inhibitor packets" as they not only provide real-time anticorrosion protection but also manifest the self-healing and self-reporting properties in different corrosive environments, including simulated body fluids (SBFs). They passivate the metal surface and provide a prolonged pathway for electrolyte and corrosive species diffusion through labyrinth effect. Their faces can be suitably tailored for better coordination, adsorption, and performance. This review offers insights into Janus materials synthesis for improved performance, highlighting both challenges and opportunities in corrosion protection.