Being impermeable to liquids and gases, graphene, a two-dimensional material made entirely of carbon atoms arranged in a hexagonal lattice, has previously been investigated as a coating to protect metals from oxidation and corrosion. However, due to its nobility and high electrical conductivity, a graphene coating can form a galvanic cell with the metal to be protected, eventually enhancing the oxidation and corrosion processes.

Hexagonal boron nitride (BN) has been suggested as an alternative to graphene for coatings of metals. Indeed, graphene and BN have the same hexagonal structure and comparable impermeability to gases [Bunch JS, Nano Lett 2008], but since BN is an electrical insulator, it does not cause galvanic corrosion. Here we present a comparative study showing that BN coatings are superior to graphene coatings for long-term protection of copper substrates against oxidation. The evolution of Raman signals for copper oxides in bare, graphene- and BN-coated copper samples during two different series were measured. In the first series, samples were kept at 50°C for  60 hours, while in the second series the samples were heated from room temperature up to 400°C within 45 minutes. The results indicate that while both graphene and BN offer good short term protection, BN-coatings offer superior protection in the long term.