Highlights GNP-pigmented films show exceptional resistance to cathodic delamination.  Oxygen-diffusion shown to be the rate-limiting step in the presence of GNPs.  Delamination rates correlate with through-coating oxygen permeation rates. A primer coating system adherent to iron substrates based on graphene nano-platelets (GNPs) dispersed in polyvinylbutyral (PVB) is presented. Using a scanning Kelvin probe (SKP), the composite coatings are shown to exhibit exceptional resistance to an important corrosion-driven failure process, namely cathodic delamination, when aqueous chloride electrolyte is introduced to a penetrating coating defect. Delamination rate kinetics are shown to correlate strongly with reductions in the rate of oxygen permeation through the coating with increasing GNP pigment volume fraction.

Smart-release inhibition of corrosion driven organic coating failure on zinc by cationic benzotriazole based pigments. Corrosion Science

Graphene nano-platelets (GNP) reduce corrosion-driven cathodic delamination rates.  GNP act principally to slow through-coating oxygen diffusion when coated on iron.  When the GNP are coated on zinc, a galvanic couple is formed.  The galvanic coupling of the GNP and zinc may displace cathodic oxygen reduction.

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The electronic and diffusion-blocking properties of graphene nano-platelets (GNPs) are quantified with a view to understanding their action as (possible) additives to anti-corrosion coatings. Platelet size and thickness are determined by SEM and BET specific surface area measurements. A Scanning Kelvin probe is used to show that a contact potential of up to 1.4 V develops between GNP particles and various metal substrates: silver, copper, iron and zinc. A novel photochemical method is used to show that oxygen permeation rates through a PVB-GNP (polyvinylbutyral) composite coating decrease by over an order of magnitude as GNP volume fraction increases to 0.056.