Next-Generation Sacrificial Anodes for Cathodic Protection: Alloy Design, Smart Materials, Artificial Intelligence and Sustainability—A Critical Review

Sacrificial-anode cathodic protection remains one of the most widely applied corrosion mitigation strategies for metallic structures exposed to marine, freshwater, soil and industrial environments. Conventional zinc-, aluminum- and magnesium-based anodes have demonstrated long-standing practical value; however, increasing demands for extended service life, predictable electrochemical performance, environmental compliance and digital monitoring are reshaping the design criteria of modern cathodic protection systems. Recent research has therefore shifted from empirical alloy selection toward microstructure-controlled alloy design, smart sensing integration, data-driven prediction and sustainability-oriented material development. This critical review examines the evolution of sacrificial-anode technologies from conventional alloy systems to next-generation multifunctional anodes. Particular emphasis is placed on the relationship between alloy composition, microstructure, phase distribution, manufacturing route and electrochemical performance. The review further evaluates emerging smart sacrificial anodes incorporating embedded sensors, wireless monitoring and structural health monitoring functions, as well as the growing role of artificial intelligence, machine learning, digital twins and numerical simulation in corrosion prediction and anode lifetime assessment. Sustainability aspects, including lifecycle assessment, carbon footprint, recyclability, regulatory pressure and critical raw material dependency, are also critically discussed. This review differs from conventional alloy- or application-centered summaries by applying a four-part assessment structure: composition–processing–microstructure relationships; electrochemical and service-environment validation; sensing and data-driven lifetime management; and lifecycle sustainability. The structure is used to compare evidence maturity, identify application-specific failure modes and translate research gaps into qualification priorities. Current challenges include the lack of standardized performance datasets, limited long-term field validation, inconsistent correlation between laboratory and service environments, and insufficient integration of environmental metrics into anode design. Future research should focus on data-rich alloy development, sensor-enabled anode systems, predictive lifetime models and sustainable material selection strategies. The review concludes that next-generation sacrificial anodes will increasingly be defined not only by electrochemical efficiency, but also by intelligence, durability, environmental responsibility and system-level reliability.