Electrochemical deposition of graphene-doped polyaniline films for enhanced zinc corrosion resistance

Abstract

• Successful electrodeposition of polyaniline (PANI) coatings without any corrosion of the zinc substrate. • Incorporation of graphene (GR) or of graphene nanoplatelets (GRNP) improves the crystallinity of PANI coatings. • Vickers hardness of the PANI coatings increased with the incorporation of GR and of GRNP. • The GR-doped and GRNP-doped PANI coatings exhibit much greater corrosion protection of zinc than pure PANI in 0.1 M NaCl. Pure polyaniline (PANI), graphene-doped PANI (PANI-GR), and graphene nanoplatelet-doped PANI (PANI-GRNPs) coatings were electrodeposited galvanostatically from an aqueous solution of sodium salicylate and aniline onto zinc substrates. Graphene was obtained via the electrochemical exfoliation of graphite in an acidic medium. Prior to incorporation into the composites, both forms of graphene were dispersed in the surfactant SDS. The electrochemical behaviour of the bare and coated substrates was evaluated in 1 M NaCl. The study demonstrates that electrodeposition via galvanostatic mode is an effective method for coating zinc substrates with polyaniline (PANI) and PANI-graphene composites. Structural analyses using X-ray diffraction (XRD) and Raman spectroscopy confirmed the successful integration of graphene into the PANI matrix. The incorporation of graphene significantly improved the coating quality, enhancing surface homogeneity and minimizing the formation of surface cracks. Mechanical testing revealed that PANI-GR composite coatings exhibited superior microhardness compared to pure PANI and PANI-GRNPs coatings. The PANI-GR coatings outperformed the corrosion resistance of both bare zinc and pure PANI coatings. This enhanced corrosion resistance is attributed to the improved barrier properties, more noble corrosion potential, decreased anodic and cathodic branches and enhanced charge transfer mechanisms facilitated by graphene incorporation.

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