Reduction of hydrogen permeation

For hydrogen tanks and the like, metallic materials (e.g. steel or aluminum) are still predominantly used today, either as solid materials or as liners in polymeric materials, which constitute an enormous additional weight. In order that lightweight materials such as fiber reinforced polymers can also be used for fuel tanks etc., which do not provide a sufficient barrier to hydrogen permeation themselves, Fraunhofer IFAM is developing barrier coatings which strongly reduce the permeability of hydrogen and thus offer versatile possibilities for lightweight construction in the aerospace industry, but also in other areas.

Development of a barrier coating for inner walls of fuel tanks in the "CryoCoat" project

The experts at Fraunhofer IFAM in the field of paint technology have a broad range of expertise in the development of barrier coatings against gases and liquids for a wide variety of applications. The focus here is particularly on the area of hydrogen barrier coatings and the need for these coatings affects not only the aerospace industry, but also the transportation industry and the entire hydrogen energy sector.

For the space sector, barrier coatings for the inner walls of fuel tanks to prevent hydrogen permeation have been successfully developed in recent years. The goal is to be able to use lightweight materials such as fiber reinforced polymers for the construction of the tanks, which themselves do not provide an adequate barrier against hydrogen. The fuel tanks are used for liquid hydrogen (LH2), but gaseous hydrogen is also present above the liquid. The barrier coating should work for hydrogen in both states of aggregation.

The coating solution developed as part of the "CryoCoat" project is based on a polymeric binder containing platelet-shaped pigments on a metal or silicate base, which form the actual diffusion barrier. The formulations can be processed using paint technology and can also be applied to large structures via spray application. As part of the space project, a prototype coating was developed whose barrier effect against hydrogen could be demonstrated.

Ongoing development of barrier layers in funded projects

This coating, developed in the "CryoCoat" project, is currently being adapted in other projects. In the "TransHyDE" project, the coating is being tailored for use in gas pipelines and tanks for storing hydrogen as an energy carrier, as completely different requirements are imposed on the coating for this application. Here, Fraunhofer IFAM is also applying its extensive know-how in the development of barrier coatings against gases and liquids in order to develop the ideal coating for the particular application. In the "TransHyDE" project, barrier coatings with excellent barrier properties against hydrogen were already developed within the first year of the project.

In the "HyBit" project, a broad-based consortium has been working on the industrial transformation to a hydrogen economy since fall 2022. In this project, the department for Paint Technology is investigating how barrier coatings can help to retrofit the existing gas infrastructure to meet the special requirements for hydrogen transport.

Testing of barrier layers by determination of hydrogen permeation

At Fraunhofer IFAM, the developed barrier coatings can also be tested for their effectiveness using a hydrogen permeation measuring device. Therefore, a rapid check of the development progress can be ensured during coating development.

In the Paint/Lacquer Technology department of Fraunhofer IFAM, the development projects on barrier coatings are headed by Dr. Andrea Deißenberger. Within these projects, barrier coatings are developed for a wide variety of industrial sectors, such as the packaging industry, the electronics sector and the transportation sector, with a particular focus on the aerospace industry, and are specifically adapted to the special requirements of the individual sectors.