Graphene based coatings for corrosion protection

Feng Yu

    Research output: Book/ReportPh.D. thesis

    2837 Downloads (Pure)

    Abstract

    Owing to its impermeable nature, graphene is an excellent candidate as a barrier material for application in anticorrosive coatings. Although, graphene is reported to be able to reduce the corrosion rate of metals, enhanced corrosion due to the galvanic coupling between the conductive graphene layer and metal substrate is also well-established. Corrosion can initiate from graphene defects, which emphasizes the importance of the graphene layer to be of high quality. The weak adhesion of graphene on metals influences its practical use in anticorrosive coatings, especially at long-term exposure to corrosive environments. Furthermore, large-scale high-quality chemical vapor deposited (CVD) graphene can only be grown effectively on a few metal substrates and is difficult to apply onto rough surfaces, both of which significantly limit the universal use of graphene on substrates in practical use. Furthermore, industrially relevant alloys such as steel cannot withstand the high temperature (~1000°C) required for traditional CVD graphene growth process, without compromising the structural and mechanical integrity.
    To address these common challenges of most graphene based anticorrosive coatings, both multilayer graphene (MLG) coatings and a polymer-graphene hybrid coating are reported in this thesis. Our results show that MLG coatings provide effective long-term protection for stainless steel in boiling seawater because of prolonged diffusion pathway for corrosion species. However, the MLG coating grown on Ni substrate fails in acidic media, due to hydrogen bubbles formation at the coating-substrate interface, which eventually lead to delamination of the coating. The hybrid coating, on the other hand, is prepared through a layer-by-layer transfer process with alternating polymer and graphene layers. Results show that graphene enhanced coatings consistently exhibit far better corrosion protection performance than both reference polymer coatings with same thickness, and bare graphene layers directly on metal. The number of graphene layers in the hybrid coating plays an important role in the overall performance. The hybrid coating with only one graphene layer cannot effectively protect aluminum alloys after 30 days of immersion in simulated seawater, while the hybrid coating with two graphene layers completely inhibits corrosion even at 120 days of immersion. The polymer graphene hybrid coating is also effective for corrosion protection on brass and steel substrates and it is anticipated to provide high performance anticorrosive coatings for various metals and alloys.
    Original languageEnglish
    PublisherDTU Nanotech
    Number of pages192
    Publication statusPublished - 2018

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