Corrosion performance of a steel surface modified by a robust graphene-based superhydrophobic film with hierarchical roughness

Abstract

Potentiostatic deposition of cobalt film and cobalt-graphene, Co-G, composite, followed by modification with low surface energy stearic acid (SA), was used to fabricate superhydrophobic films on a steel substrate successfully. A scanning electron microscope was used to analyze the surface morphology of the prepared superhydrophobic cobalt film modified by stearic acid, Co-SA, and the cobalt-graphene film modified by stearic acid, Co-G-SA. The findings show that both the fabricated films have micro-nanostructures. The Co-G-SA film shows a higher roughness due to the network structures of graphene and so exhibits higher superhydrophobicity. The Fourier transform infrared spectrophotometer, FTIR, results confirm the formation of Co-SA and Co-G-SA films on the steel surface. The wettability of the prepared films shows that they exhibit superhydrophobicity, where the Co-SA and Co-G-SA films have contact angles of 155° and 158°, respectively. The Potentiodynamic polarization results show that the value of the corrosion current density for steel coated with Co-SA (0.7094 µA) is lower than that of bare steel (0.1457 mA), while the coated steel with Co-G-SA film has the lowest value (0.1732 µA). The electrochemical impedance spectroscopy, EIS, results show that the charge transfer resistance for steel coated with Co-SA is 38 times that of bare steel, while steel coated with Co-SA is 57 times that of bare steel. Potentiodynamic polarization and EIS results show that the prepared Co-G-SA film superhydrophobic films exhibit higher corrosion resistance. Co-G-SA film has higher mechanical stability (maintains superhydrophobicity until 900 abrasion cycles), chemical stability (has superhydrophobicity in the pH range 1–13), and long-term stability (retains superhydrophobicity after 30 days in a 0.5 M NaCl solution) in 0.5 M NaCl solution.