Hydrogen barriers are required in aerospace and automotive industries, as well as for energy generation and conversion processes where materials are exposed to hydrogen environments. These barriers are essential in preventing hydrogen incorporation into materials that can otherwise cause detrimental effects such as hydrogen embrittlement. This effect is due to hydrogen atoms occupying interstitials in the crystal lattice and thereby inducing increased brittleness and reduced fracture toughness. Especially PVD processes offer the opportunity of tailoring the coatings composition and microstructure and are known for producing thin but dense and well-adhered coatings. However, they suffer from substrate contaminations and growth defects like pinholes, limiting their performance as permeation barriers. 

It is crucial to analyze the effectiveness of coatings through application-related tests. By utilizing custom-built, gas-phase hydrogen permeation test benches, we can directly assess how defects, deposition methods, microstructures, and other factors impact the barrier properties against hydrogen.

For depositing oxidic barrier layers on ferritic steel membranes, we employed reactive RF sputtering and HiPIMS processes. Scanning electron microscopy, X-ray diffraction analysis and Raman spectroscopy was used to identify and quantify defect density.

Our results demonstrate that defects significantly affect the hydrogen barrier effect. However, further extensive investigations are needed to gain a deeper understanding of material-dependent defects and their impact on barrier performance.