Beyond the performance of traditional corrosion protective pigments: A comparative study

 
Pigments for anti-corrosion coatings may serve to protect the underlying metal by sacrificial, inhibitive or barrier mechanisms. Barrier coatings offer a passive means of metal protection by extending the diffusion pathway though the coating. Graphene has the potential to offer increased tortuosity to a coating, above that of traditional pigments such as glass flake, micaceous iron oxide and aluminum flake. In considering graphene as an alternative barrier pigment, it is important to understand its performance benefits over traditional pigments. The authors demonstrate such benefits through additions of both graphene and traditional pigments to a C4/C5 primer, with a suite of tests applied to each coating, including neutral salt spray combined with impedance spectroscopy (EIS), constant immersion EIS and water vapour transmission. The tortuosity of each system is examined and related to coating performance. EIS indicates that graphene within the coatings prolongs the breakthrough of electrolyte to the metal/coating interface by up to 1440 hours post NSS exposure, significantly above that of traditional pigments. Such coating types also exhibit the lowest levels of corrosion creep.