Flexible Barrier Coatings for Harsh Environments
Current hydrogen systems within fuel cell electric vehicles (FCEV) and the supporting infrastructure to compress, store and deliver hydrogen fuel are prone to systemic inefficiencies and poor reliability, which hobble the economic competitiveness of FCEVs. Many of these reliability problems stem from plastic and elastomer seals (O-rings, gaskets, and piston seals) employed in hydrogen systems that leak and eventually fail. Failure mechanisms are related to hydrogen ingress into the seal (i.e. blistering and extrusion) and frictional wear, both of which are exacerbated by the wide pressure and temperature swings experienced by the seals. The result is that these seals require frequent replacement incurring significant labor costs and excessive equipment downtime. GVD Corporation has adapted its novel vapor deposition technology to encapsulate seals with two types of protective coatings to extend their life in hydrogen compression, storage and delivery applications. The first coating type is a multilayer gas barrier coating which reduces gas permeation into/out of plastic and rubber materials. The chemistry and architecture of these flexible coatings are engineered to dramatically inhibit gas permeation while ensuring durability during repeated loading applications and preserving the mechanical properties of the underlying elastomer seal. The second coating type is a modified version of GVD’s lubricious PTFE coating used for mold release and other seal applications. The PTFE coating makes seals more resistant to wear caused by mechanical motion or thermal expansion/contraction and swelling from hydrogen saturation. Both types are well suited for three-dimensional seals since they deposit uniformly over parts with complex geometries. The primary outcomes of the project were as follows: GVD’s PTFE coatings reduce friction experienced by rigid plastic seals in hydrogen compressors, leading to 70% reduction in mass loss rates and 300% increase in lifetime. Three-fold increased seal lifetimes are predicted to lead to a reduction in station maintenance costs of $0.25/gge hydrogen. Seal lifetime increases were observed for both Hofer and Hydropac compressor seals. PTFE-coated seals allowed 6% lower hydrogen fuel loss which will reduce final delivery costs by at least $0.12/gge hydrogen in addition to the savings on station maintenance costs. GVD’s PTFE coatings had a positive impact on rubber O-ring wear, resulting in 40x increased seal life in high pressure conditions in testing by Takaishi Industry Co. GVD’s gas barrier coatings reduce helium permeability of rubber materials by 80%, which will reduce the occurrence of blistering in seals subject to rapid pressure swings in hydrogen service. GVD designed a full-scale tumble coater for o-ring coatings with the gas barrier coating by plasma enhanced iCVD. The improvements in seal lifetime afforded by GVD’s coatings will directly contribute to meeting cost targets set in the HFCTO multiyear plan for hydrogen infrastructure development.
- Research Organization:
- GVD Corporation
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
- DOE Contract Number:
- SC0011339
- OSTI ID:
- 1787996
- Type / Phase:
- SBIR (Phase IIA)
- Report Number(s):
- DOE-GVD-11339-2
- Country of Publication:
- United States
- Language:
- English
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