Synthesis of low-electrical-conductivity graphene/pernigraniline composites and their application in corrosion protection

Graphene can be a corrosion-promotion material because of its high electrical conductivity. This paper aims at eliminating the undesired corrosion-promotion effect of graphene, and reports a promising application of graphene/pernigraniline composites (GPCs) for the corrosion protection of copper. The composites were synthesized by an in situ polymerization-reduction/dedoping process. The synthesized composites have a flake-like structure, and their conductivity is as low as 2.3 x 10(-7) S/cm. The GPCs are then embedded into polyvinylbutyral coating (PVBc) to modify the coating. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements reveal that the GPC-modified PVBc is an outstanding barrier against corrosive media compared with pernigraniline or reduced graphene oxide (rGO) modified PVBc. Scratch tests also show that the corrosion-promotion effect of rGO in GPCs is inhibited. The enhanced corrosion protection performance is observed because on the one hand the pernigraniline growing on rGO surface avoids graphene-graphene/metal connections increasing the electrical resistance of coating; on the other hand the as-prepared GPCs are less flexible than polymer-free rGO and they are more likely to unfold during the coating process, which can greatly prolong the diffusion pathway of corrosive media in the coating matrix. (C) 2014 Elsevier Ltd. All rights reserved.