Graphene oxide reinforced NiPCo composite coatings: Optimum graphene oxide content for improved anticorrosion and wear resistance

Abstract

Graphene oxide (GO)-reinforced NiPCo composite coatings were fabricated on steel substrates via pulse electrodeposition to investigate the effects of GO content on coating properties. The study examined how varying GO concentrations influenced morphology, chemical composition, growth mechanisms, mechanical properties, wear resistance, electrochemical stability, and wetting behavior. GO incorporation led to significant improvements in both corrosion and wear resistance. The refined microstructure enhanced nucleation during electrodeposition, contributing to superior performance. The optimized value of GO concentrations was 100 mg/L, suggesting the superior properties for all properties at only one value (100 mg/L GO), not only for friction coefficient and wear rate, but for Corrosion resistance. Wear testing revealed substantial reductions in both the friction coefficient (0.3) and wear rate (∼6 × 10⁻⁶ mm³/Nm), corresponding to ∼33 % and ∼ 79 % decreases, respectively, under a 2 N load. These improvements were attributed to the uniform distribution of GO within the coating matrix, enhancing load-bearing capacity and self-lubricating effects. Additionally, the worn surface showed greater smoothness and uniformity, promoting stable sliding. Corrosion resistance was assessed through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Corrosion rates decreased with increasing GO content, reaching optimal performance at 100 mg/L GO concentration. Density Functional Theory (DFT) analysis confirmed the formation of a corrosion-resistant passive oxide layer, with the NiPCo/GO (100 mg/L) coating displaying the highest impedance value (7700 Ω·cm²), indicating superior corrosion resistance.