A bi-layer orientated and functionalized graphene-based composite coating with unique hydrogen gas barrier and long-term anti-corrosion performance

Conventional hydrogen gas barrier composite coatings were facing low corrosion resistance and adhesion level issues, both of which could lead to high risks of hydrogen-related equipment failure. Herein, a unique bi-layer composite coating consisting of primer thermoplastic polyurethane (TPU) layer and top phenylenediamine (PPD) non-covalent modified orientated graphene (Gr-PPD) incorporated epoxy resin layer was prepared by a two-step high-speed spinning method. Orientated Gr-PPD due to high shearing force during spinning procedure and improved interfacial bonding between polymer and inorganic phases by amino groups interactions with EP during curing reaction created effective barriers and reduced free volume spaces in EP, beneficial for preventing the diffusion of hydrogen gas and corrosive media. In addition, surface dangling bonds existed on surface of Gr-PPD could position hydrogen atoms by C–H sp3 bond, reducing the hydrogen permeation as well. The primer TPU coating was another protective layer to hinder hydrogen permeation and Gr conductive network formation. The |Z|0.01Hz value of optimum sample maintained 3.72 × 1011 Ω cm2 for 90-day immersion in 3.5 wt% NaCl solution and tolerated 60d incessant salt-spray attack. Plus, it showed 82.9% decrease in H2 permeability coefficient and high adhesion strength of 11.5 MPa, which presented high applicability in industrial environment.