Hydrogen Permeation Barrier Layers for the Hydrogen Economy

A hydrogen-based economy relies on the use of steel components such as containers for storage, pipelines for transport, or bipolar plates in fuel cells. All these components suffer from hydrogen embrittlement if common, inexpensive steels are used. For a widespread application of hydrogen, hydrogen ingress into and through the steel must be minimized. A powerful solution is hydrogen permeation barrier layers. They can be obtained by surface modifications using chemical treatments such as nitriding or carburizing and mechanical treatments such as peening, or by deposition of protective coatings. In this review, hydrogen embrittlement mechanisms and the role of individual defects are briefly described, followed by a detailed description of the advantages and disadvantages of the different types of hydrogen permeation barrier layers. As the mechanical properties of the layers are important for applications, an outlook on how small-scale mechanical tests can be used for their characterization is presented.