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 × 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.