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  for Metal Finishing since 1989
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Coatings for Aluminum to be used in high purity applications

I am working on a new design for a pressure vessel that will store both De-Ionized water and hydrogen at approx. 300 PSI. I would like to build it out of Aluminum but I cannot have anything leech out of the aluminum. What coatings are there available that are very inert, not terribly expensive, and stay on the aluminum.

Richard Dubey
- Rocky Hill
2001

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Tin is about the best coating on metals to resist corrosion from water, as the solubility of tin oxide is very low. A conformal thick plating of pure tin is a standard for storing high purity water. If the purity requirements are not in the ppb range and the pH of the water never falls outside of a 6-8 range, a transition metal oxide would probably be sufficient. Conformal coating and 100% coverage is key, especially with aluminum.

It is going to be tough to store hydrogen at 300psi in aluminum for any length of time, however, as hydrogen can and will diffuse into and through the aluminum (hydrogen will diffuse through steel too).

Dale Woika
- Bellefonte, Pennsylvania, USA
2001

Electroless Nickel is used on the inside of aluminum cylinders for hydrogen storage . I would think electroless nickel would be fine for DI water also.

Todd Osmolski
- Charlotte, North Carolina, USA
2001