Waterborne Polyurethane for Wind Turbine Blade Corrosion Protection: Synthesis, Modification Strategies, and Performance Advances

Wind turbine blades are exposed to multiple coupled stressors requiring protective coatings with ultra-low volatile organic compound (VOC) content, thick-film capability, and long-term durability. This review critically evaluates waterborne polyurethane (WPU) coatings as a sustainable solution, benchmarking five synthesis routes—prepolymer emulsification, acetone process, melt dispersion, ketimine/ketazine chemistry, and self-emulsification—with prepolymer emulsification identified as the most industrially mature method. Key modification strategies are systematically compared, including nano-reinforcement, surface energy control, self-healing chemistries, and bio-based approaches. Based on a synthesis of laboratory, wind-tunnel, and field studies, three critical bottlenecks—thick-film formation, nanofiller dispersion, and long-term weatherability—are identified. To address these, a layered coating architecture is proposed, integrating a low-surface-energy topcoat, a lamellar-barrier mid-coat, and a post-crosslinked primer. This framework aims to guide the industrial deployment of WPU thick-film blade coatings in offshore and other extreme environments.