The Structural Stability of Graphene Anticorrosion Coating Materials is Compromised at Low Potentials.

Corrosion of engineered structures is a major problem causing an estimated economic loss of more than 2 trillion US dollars annually worldwide. Graphene has recently emerged as highly promising, low-cost, and transparent anticorrosion coating material. Herein, it is shown that a multilayer graphene film grown on Ni by chemical vapor deposition undergoes abrupt stability failure under galvanic-corrosion conditions. The multilayer graphene coating was examined by optical microscopy, SEM, energy dispersive X-ray spectroscopy, Raman spectroscopy, and cyclic voltammetry after exposure to potentials between 600 and 1300 mV in alkaline solution. A fast and simple electrochemical method is proposed to sensitively quantify the damage caused by the applied potential bias. It is based on quantification of the oxidation signals generated by the underlying Ni-metal catalyst that is exposed by damage to the graphene film. It is shown that film damage can start at potentials as low as 900 mV and that macroscopic and extensive damage can be caused at potentials above 1000 mV. In addition, once the graphene film has been damaged, the corrosion rate of the underlying metal is significantly increased. These findings are of great importance for potential applications of multilayer graphene films in coating metal structures with huge industrial and economic implications.