Despite graphene's apparent potential for anti-corrosion coatings, it is cathodic to most metals and can promote corrosion at exposed graphene–metal interfaces. This may accelerate dangerous localized corrosion that can seriously weaken the coated metals.
We thank Y.W. Chung and A.R. Koltonow for helpful discussions, F. Frankel for advice on Fig. 1, and the Office of Naval Research (ONRN000141612838) for support.