Preparation and hydrogen permeation resistance of α-Fe₂O₃/Al₂O₃ composite coating via atomic layer deposition and plasma treatment

The hydrogen isotope permeation barrier (HIPB) plays a crucial role in preventing hydrogen penetration in the hydrogen energy industry. Unlike the well-documented HIPB oxidations such as Al₂O₃, TiO₂, Cr₂O₃, and Er₂O₃, rarely used α-Fe₂O₃ was applied as an intermediate layer in this study. An α-Fe₂O₃/Al₂O₃ HIPB was synthesized on T91 steel substrates via atomic layer deposition (ALD) and oxygen plasma treatment. By adjusting the applied power upon plasma treatment, α-Al₂O₃ was derived at 650 °C, facilitated by both the additional energy of ion bombardment and template effect of α-Fe₂O₃. The interfacial α-Fe₂O₃(104)/α-Al₂O₃(104) relation was observed, and the adsorption energy of H atoms in the interface region was calculated using the density functional theory (DFT) method. The experimental results of hydrogen permeation performance and corrosion resistance of the composite coatings indicate that the α-Fe₂O₃/Al₂O₃ HIPB shows excellent hydrogen-permeation resistance, outperforming previously reported HIPBs, providing a new approach for the preparation of high-performance hydrogen-resistant coatings.