Layer-by-layer assembled graphene oxide-enhanced poly(vinyl alcohol)/polyurethane coatings on stainless-steel substrate as hydrogen barriers

The development of coatings with high hydrogen-resistant properties is of great significance due to the enormous hazards caused by hydrogen embrittlement during hydrogen storage and transport via metal-based containers or pipes. Multi-structured composite coatings showed advanced hydrogen-resistant behaviors compared to conventional ones, such as metal oxides (i.e., Al2O3), nitrides (i.e., SiN), and carbides (i.e., SiC), etc. In this study, the graphene oxide (GO) doped-polyvinyl alcohol (PVA)/polyurethane (PU) composite coating was prepared by GO in PVA solution assembling with PU emulsion via layer-by-layer process on a stainless-steel substrate. The cross-linking reaction between PVA and PU solved the adverse effect of GO agglomeration in the hydrogen barrier coating. Meanwhile, PU improved the mechanical properties, hydrophilicity, and thermal stability of the coating. It was found that 2.0 wt% GO doped-PVA/PU composite coating exhibited an extremely low hydrogen permeability of 0.72 cm3/(m2·d·0.1 MPa), which was significantly reduced by 56.81 % compared to the bare substrate and by 33.70 % compared to the pure PVA coating. The toughness of the coating was increased by 98.05 %, the surface contact angle was increased to 42.8°, the stability and adhesion ability to the stainless-steel substrate were also significantly improved. The designed coating effectively addresses the limitations of traditional polymer coatings, such as poor adhesion and peeling off from stainless-steel substrates, offering a more robust, reliable, and durable solution for protecting stainless steel in complex environments.