Long-Term Durability and Stabilization of Polyurea Protective Coatings: Degradation Mechanisms, Interfacial Engineering, and Lifetime Prediction

Polyurea protective coatings are widely used in anticorrosion, waterproofing, marine engineering, transportation infrastructure, and industrial protection because of their rapid curing, high toughness, strong adhesion, and resistance to aggressive media. However, their long-term reliability depends not only on initial mechanical performance, but also on barrier retention, coating/substrate interfacial stability, and resistance to environmental aging. This review examines the durability and stabilization of polyurea protective coatings from the perspective of organic coating degradation. The effects of molecular architecture, hydrogen-bonding networks, hard/soft segment microphase separation, curing behavior, and interfacial structure on coating stability are first discussed. Aging and failure mechanisms under ultraviolet irradiation, thermo-oxidative exposure, hygrothermal conditions, salt spray, marine environments, cyclic loading, and mechanically coupled service conditions are then reviewed, with emphasis on water and ion transport, hydrogen-bond disruption, microphase relaxation, crack evolution, adhesion loss, and barrier failure. Stabilization strategies involving molecular structure regulation, nanofiller-induced barrier enhancement, interfacial engineering, dynamic networks, self-healing systems, recyclable designs, and lifetime prediction are further evaluated. The available evidence shows that polyurea coating failure is rarely governed by a single degradation pathway; rather, it results from the coupled evolution of chemical aging, moisture and ion diffusion, microphase rearrangement, interfacial damage, and mechanical defects. Future research should focus on standardized aging protocols, in situ characterization, structure-durability relationships, and data-driven lifetime prediction to guide the design of durable polyurea coatings for long-term protective applications.