Self-unfolded graphene for corrosion protection

•Self-unfolded rGO (S-rGO) is prepared via reducing GO in the presence of SPANi.•Protection property of S-rGO/epoxy coating is better than that of crumpled-rGO/epoxy coating.•S-rGO is an effective and desirable enhancer for protection property of coatings. Inevitable crumpling and folding of graphene in coating matrix restricts the enhancement of corrosion protection properties of graphene-based coatings. Herein, reduced graphene oxide with self-unfolded morphology (S-rGO) and crumpled morphology (C-rGO) were prepared. Compared with C-rGO, S-rGO exhibits a higher performance in enhancing the corrosion protection properties of epoxy coating because S-rGO possesses larger effective aspect ratio and projected area in the direction perpendicular to the diffusion path of aggressive species so that its impermeable domains can force aggressive species to overcome the coating matrix via migrating along longer diffusion paths.