Advancements and Challenges in Coatings for Wind Turbine Blade Raindrop Erosion: A Comprehensive Review of Mechanisms, Materials and Testing

Raindrop erosion of wind turbine blades’ leading edge is a critical degradation mechanism limiting wind turbine blade lifetime and aerodynamic efficiency. Protective coatings have been extensively studied to mitigate this damage. This review critically synthesises current knowledge on coating-based protection strategies against erosion, with emphasis on (i) the underlying mechanisms of erosion, (ii) advances in conventional and emerging coating technologies, and (iii) experimental approaches for testing and lifetime prediction. Across reported studies, nanofiller reinforcement (e.g., CNTs, graphene, CeO2, Al2O3) enhances erosion resistance by 60–99%, primarily through improved toughness and stress-wave dissipation. Hybrid and multifunctional systems further combine mechanical durability with self-healing or anti-icing capabilities. Experimental results confirm that erosion rate follows a power-law dependence on impact velocity, with maximum damage occurring between 45° and 60° impact angles. Softer elastomeric coatings demonstrate longer incubation periods and superior viscoelastic recovery compared with rigid sol–gel systems. Persistent gaps include the lack of standardised testing, poor field–lab correlation, and limited long-term durability data. Future work should focus on coordinating multi-stressor testing with variable-frequency rain setups to replicate real field conditions and enable reliable lifetime prediction of next-generation erosion-resistant coatings.