Mitigating Hydrogen Ingress with Thin Cloaking Liquid Barrier Films

As hydrogen energy systems advance globally, management of hydrogen ingress remains a significant challenge. When hydrogen gas contacts a metal, it dissociates into hydrogen atoms, which subsequently enter and embrittle the metal. This detrimental process not only affects hydrogen pipelines but also metal components in aqueous corrosive environments, such as heat exchanger tubes in geothermal systems. Disrupting hydrogen ingress at the metal interface is therefore crucial to prevent subsequent embrittlement within the metal. Here, we show that cloaking liquid films as thin as 1 nm minimize hydrogen ingress into steel. These films, made from Krytox lubricant, are immiscible with water and preferentially wet steel in aqueous environments. Using a Devanathan–Stachurski electrochemical permeation cell, we show that in mildly acidic electrolytes, cloaking liquid films reduce hydrogen diffusivity in steel by 80% and the subsurface hydrogen concentration, a measure of hydrogen uptake in the steel, is decreased by 86%. X-ray photoelectron spectroscopy confirms the stability of the cloaking barrier film after 25 h of accelerated electrochemical permeation testing. In alkaline environments, similar reductions in hydrogen diffusivity (82%) and subsurface hydrogen concentration (90%) were observed, demonstrating the versatility of these films as barriers to hydrogen ingress. Additionally, we apply these thin cloaking films to enhance the barrier properties of defective zirconia coatings on steel. Although zirconia impedes hydrogen ingress, pinhole defects in the zirconia coating can provide pathways for hydrogen entry. We show that thin cloaking liquid films combined with a 75 nm zirconia coating reduce hydrogen diffusivity in steel by 84%, even when defects are present. Thicker composite coatings of zirconia and lubricant-impregnated microtextured surfaces could further enhance long-term protection against hydrogen ingress in practical applications.