Interfacially engineered polypyrrole/ZIF-8 based bilayer nanocomposite coating for sustained active-passive protection of stainless steel

The development of intelligent coatings shows great potential for sustained corrosion protection. In this study, ZIF-8 was combined with graphene oxide (GO) and the corrosion inhibitor 1,10-Phenanthroline (Phen) to prepare PZ 8 G nanomaterials. These nanoparticles were introduced into a dispersed carbon nanotube enhanced water-borne acrylic epoxy resin to fabricate a corrosion inhibition coating (PZ 8 G/DCE), followed by electrodeposition of a polypyrrole (PPY) outer film to construct a PZ 8 G/DCE/P bilayer architecture with enhanced anti-corrosion performance. The PZ 8 G composites exhibited improved compatibility with acrylic epoxy resin compared to pristine ZIF-8, and the PZ 8 G/DCE/P bilayer coating presented satisfactory adhesion. This coating effectively enhanced the corrosion resistance of 304SS in both acidic and saline environments, increasing the corrosion potential by 0.36 V and 0.3 V, respectively. The coating demonstrated significant efficacy in acidic conditions, in which the EIS tests confirmed stable protection over 30d of immersion, while SEM characterization after 60d of immersion revealed it maintained structural integrity with minimal morphological changes. Furthermore, the self-healing capability of PZ 8 G/DCE/P coating system was verified through EIS measurements on artificial scratches combined with elemental analysis, which demonstrated the active release of inhibitors and the formation of protective composites at damaged region. The synergistic combination of PPY, which exhibits dual functionality as both anodic protection and physical barrier, with actively corrosion inhibiting PZ 8 G nanofillers, effectively provided a sustained active-passive corrosion protection for stainless steel under aggressive conditions. This work suggests a promising strategy for designing smart anti-corrosion materials.