Nanoparticle enhanced sol-gel coatings for erosion and fouling resistance in offshore wind turbine applications: A comparative study of metallic and carbon reinforcements

Offshore wind turbine blades are significantly affected by rain erosion, particulate impacts, and biofouling, leading to surface degradation, increased aerodynamic drag, and higher maintenance costs, thereby hindering wind energy decarbonisation goals. Addressing this challenge requires developing coating solutions that offer improved resistance to wear and biofouling, manufactured through eco-friendly, energy-efficient processes. The study introduces silica‑based hybrid sol‑gel coatings reinforced with metallic and carbon nanoparticles, providing a sustainable route to the creation of mechanically robust, hydrophobic surfaces for glass‑fiber reinforced polymer (GFRP) wind turbine blades.

Tetraethylorthosilicate (TEOS) based sol-gel formulations containing 0.1wt% commercially available silver nanoparticles (AgNPs) and multi-walled carbon nanotubes (MWCNTs) were synthesised, applied to GFRP substrates via dip-coating, and thermally cured at 120°C for 2 hours.

Material characterisation confirmed that the MWCNT-enhanced sol-gel coatings exhibited higher mechanical, thermal, and surface properties compared to the AgNPs formulation. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy analysis confirmed strong Si-O-Si network formation, with MWCNTs creating a denser structure. Water contact angle (WCA) measurements confirmed an increase in hydrophobicity with the addition of MWCNTs, effectively controlling surface energy. The TGA results showed improved thermal stability of MWCNT coatings, with lower mass loss compared to AgNPs coatings. Differential scanning calorimetry (DSC) confirmed thermal stability up to 300°C for both formulations.

Nanoindentation showed significant mechanical enhancement, with MWCNT-reinforced coatings exhibiting 26% higher hardness (0.400 vs. 0.318 GPa), a higher elastic modulus (3.24 GPa), and reduced indentation depth, indicating superior load-bearing capacity and deformation resistance. Furthermore, a preliminary droplet impact erosion test (DIEM) was performed for short periods to evaluate resistance to rain impact. Additionally, antimicrobial activity was assessed as an initial indicator of anti-fouling potential.

The study demonstrates that carbon-based nanomaterials outperform metallic nanoparticles in producing durable, hydrophobic coatings for renewable energy applications.