Graphene Coatings for Durable and Robust Resistance to Caustic Corrosion of Nickel

TL;DR

This study shows that graphene coatings can significantly improve the corrosion resistance of nickel in highly caustic environments over long periods.

Contribution

The work introduces a systematic long-term evaluation of graphene coatings on nickel in strongly alkaline conditions, a novel approach compared to prior short-term or neutral/acidic studies.

Findings

Gr_Ni graphene coating provides up to two orders of magnitude improvement in corrosion resistance compared to bare nickel.

Gr_Ni_DF coating degrades over time due to electrolyte ingress through defects.

SEM analysis confirms the structural stability of Gr_Ni under extended caustic exposure.

Abstract

Nickel is widely deployed in caustic service, yet its native Ni(OH)2/NiOOH passive film raises concerns for long service life. Graphene has emerged as a promising corrosion barrier; however, its long-term durability in strongly alkaline media remains largely unexplored. The extended exposure period in a highly caustic solution is a novel aspect of the present work, distinguishing it from previous studies that predominantly examined short-term exposures or focused on neutral and acidic environments. Here, we present the systematic assessment of low-pressure CVD-grown multilayer graphene (MLG) coatings on Ni in highly caustic (0.5 M NaOH) for up to 80 days. Two architectures, a conformal, robust MLG coating (Gr_Ni) and a less robust film (Gr_Ni_DF), were benchmarked against bare Ni. PDP and EIS reveal that Gr_Ni initially delivers nearly 2 orders of magnitude enhancement, as evidenced by the low frequency impedance, accompanied by a broad, high-fidelity capacitive plateau; the impedance still maintains 1.3–1.5 orders of magnitude superior after prolonged exposure. In contrast, Gr_Ni_DF undergoes progressive degradation, affording a modest 2-fold benefit over time, consistent with defect-mediated electrolyte ingress. SEM morphologies further corroborate these trends, confirming the superior structural stability of Gr_Ni under extended alkaline immersion.

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