From Passive Barrier to Smart Response: The Evolution of Anti-Corrosion Fillers and Their Adaptive Protection Mechanisms

Smart responsive anticorrosion fillers have significantly advanced metal protection by enabling a shift from passive physical barriers to dynamic, adaptive defense systems. This review systematically elucidates the evolutionary trajectory from traditional passive barrier fillers and inhibitor-loaded active systems to state-of-the-art smart responsive platforms that sense and respond to corrosive microenvironments. The fundamental design principles and response mechanisms are discussed, focusing on pH, chloride, electrochemical potential, and temperature/humidity stimuli. The critical role of micro/nanostructural engineering-including core-shell architectures, hierarchical porosity, and surface functional layers-in achieving on-demand inhibitor release is highlighted. Advanced strategies such as hierarchical release kinetics, synergistic inhibitor combinations, and multifunctional system-level integration are addressed. Finally, key challenges related to interfacial defects, long-term response decay, and extreme environment reliability are outlined. This work provides insights into the rational design of next-generation smart anticorrosion coatings for complex service environments. This review is expected to provide a theoretical foundation and design guidelines for the development of novel adaptive anticorrosion coatings tailored for extreme service conditions.