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Coatings that are non-permeable to hydrogen

Parts of the equipment we're using is made of 17-4 PH (H900). This is not a recommended steel to use in a hydrogen environment. Overaging the steel seems a way to better its resistance, but we're also looking for coatings. So far I've found articles about gold, zinc and aluminum being used to coat parts, but I'm not sure of their value. What materials are non-permeable for hydrogen, and can be used for coatings ?

Emiel ten Berge
- Enschede, Overijsel, the Netherlands
2002

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Virtually nothing is 100.000% impermeable to hydrogen. My thought would be 0.0015" of Electroless Nickel. That will give you 99.+%, possibly 99.9+% Less than 0.0015" will give a lower percentage at a exponential rate. Precious metals like gold and platinum will also work, but they are several times more expensive. James Watts
- Navarre, Florida
2002

Thanks, could you point me to some literature or website about this ?

Emiel ten Berge
- Enschede, Overijsel, the Netherlands
2002