Development and evaluation of superhydrophobic carbon nanotube coatings onmaraging steel: Corrosion protection, and anti-fouling characteristics

This study presents a novel and environmentally sustainable method for synthesizing high-quality carbon nanotubes (CNTs) from orange peel biomass for enhanced corrosion protection of maraging steel in marine environments. Using a one-step, catalyst-free chemical vapor deposition (CVD) process at a relatively low temperature of 600 °C, a dense and vertically aligned CNT coating was successfully deposited on the steel surface. Raman spectroscopy confirmed the structural integrity and high graphitization of the CNTs, while scanning electron microscopy revealed their uniform nanoscale architecture. Wettability analysis showed a significant transformation from the hydrophilic nature of untreated steel (water contact angle ~50°) to a superhydrophobic state (contact angle ~130°) after CNT deposition. Atomic force microscopy indicated a substantial increase in surface roughness, contributing to the superhydrophobic behavior. Electrochemical tests, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), demonstrated that the CNT-coated surface exhibited a corrosion current density three times lower and corrosion resistance five times higher than bare steel. Additionally, the impedance response increased by three orders of magnitude, confirming the coating’s effectiveness in mitigating electrochemical degradation. Long-term immersion testing in seawater containing fouling microorganisms further validated the antifouling capabilities of the CNT coating, with no visible biofouling observed after three months. These results highlight the potential of bio-derived CNT coatings as multifunctional, eco-friendly solutions for marine corrosion protection.