Superhydrophobic Functionalized Reduced Graphene Oxide–Reinforced Ni─P Composite Coatings on AISI 1018 Steel for Enhanced Corrosion and Erosion Resistance

This study reports the fabrication of a superhydrophobic Ni─P composite coating incorporating polyamine‐functionalized reduced graphene oxide (F‐RGO, Cy@f‐RGO) on AISI 1018 steel via electroless deposition. The novelty lies in the use of functionalized RGO to enhance dispersion, interfacial bonding, and barrier performance within the Ni–P matrix. The coating shows a significant increase in water contact angle from ∼80° to ∼165°, with a corresponding reduction in surface energy from 69.69 mJ/m 2 to 23.93 mJ/m 2 (∼65.66%), confirming superhydrophobicity. Microstructural analysis indicates effective filling of micro‐ and nanoscale defects, reducing porosity from 3.54% to 0.10%. Electrochemical results reveal a substantial decrease in corrosion current density (45.802 to 1.2540 µA cm − 2 ) and corrosion rate (0.4523 to 0.01502 mm/year). Mechanical performance improves markedly, with hardness increasing from ∼1.75 GPa to ∼5.7–6.7 GPa, while a slight reduction in modulus is observed. The coating also exhibits minimal weight loss (∼0.2 mg at 24 h) and enhanced impedance over 120 h in 3.5 wt% NaCl. Overall, F‐RGO incorporation provides synergistic improvements in hydrophobicity, porosity reduction, and corrosion resistance compared to conventional Ni─P systems.