SFEER Hydrogen Permeation : Finding a suitable coating for the PA6 liner

Abstract: Water Stuff & Sun are developing a hydrogen battery based on a technology called SFEER’s. The SFEER’s are spherical high-pressure gas storage containers that are the size of a tennis ball. They consist of a carbon fiber-shell that is lined on the inside with a polymer called PA6. The aim of this literature review is to present suitable materials that can be utilized as a coating on the PA6 liner in the SFEER’s to minimize the hydrogen permeability. The metallic coatings that were investigated are compounds based on chromium, boron, alu- minum and titanium. The non-metallic coatings that were investigated are lamellar inorganic components (LIC) in combination with PA6 and modified graphene oxide (GO). The coating methods that were investigated are some different PVD and CVD methods (sputter deposition, plasma enhanced CVD, ALD), electrodeposition and cold spray. The lowest permeability out of all the coatings was observed for alumina, Al2O3. Titanium nitride, TiN, was also found to have very low permeability. Since these two coatings had the lowest permeabilities they were further compared considering other factors. This resulted in alumina being chosen as the final recommendation for coating the SFEER’s. A comparison was also made to find the most suitable coating method for alumina. Cold spray was found to be very promising but if it can not be used the PVD and CVD methods are other potential candidates.