Functionalized graphene oxide: Carrier for corrosion inhibitor and barrier in waterborne epoxy coatings

The physical barrier network in polymer matrix composites can be formed by well-dispersed graphene layers, which efficiently inhibited the diffusion of corrosive molecules and improved the corrosion protection properties of the composite coatings. In this work, hydroxyethylidene-1, 1-diphosphonic acid (HEDP) was carried by graphene oxide (GO) layers through covalent bonding and dispersed in waterborne epoxy matrix, aiming for the combined effects of chemical inhibition and physical barrier. Epoxy monomer, ethylene glycol diglycidyl ether (EGDE), was grafted on GO surfaces before the reaction between GO and HEDP in order to prevent the multiple-linkage of graphene layers by HEDP, while improving the compatibility between graphene fillers and the epoxy matrix. The interlayer spacing between GO layers was enlarged from 0.79 nm to 1.03 nm by the reaction with EGDE. The impedance modulus of the composite coatings was kept above 1.5 × 109 Ω cm2 for five months by adding 0.5 wt% graphene derivatives.