Effects of thermal treatments on the hydrophobicity and anticorrosion properties of as-grown graphene coatings.

Graphene grown on metal substrates has been reported to provide efficient and robust hydrophobicity during water vapor condensation on metal surfaces. However, due to the intrinsic negative coefficient of thermal expansion (CTE) of graphene, the potential thermal stress in real application environments can cause CTE mismatch and then damage the protective graphene coatings, leading to loss of surface hydrophobicity and anticorrosion properties. In this study, the effect of thermal treatments on anticorrosion properties and subsequent hydrophobicity of the graphene surface has been investigated. The as-grown graphene on nickel (Ni-Gr) is explored in terms of survival under severe thermal cycling (up to 14.62 °C s) and effectively maintains its surface properties. As a comparison, the as-grown graphene on copper (Cu-Gr) easily peeled off from the metal surface due to the thermal stress and intercalation of oxides. The thermal treatment at 200 °C under ambient atmosphere can elevate the corrosion rate 2.2 times and 29 times on the Ni-Gr and Cu-Gr surfaces compared to situations without thermal treatments, respectively. This study shows that the Ni-Gr surface is significantly more robust than the Cu-Gr surface as a sustainable hydrophobic surface in a complicated thermal environment.