i've got an application that we're currently specifying both iron phosphate and zinc phosphate.  the coating is being used on surge tanks to act as a primer on the outside of the tank, and as a mild corrosion preventer on the inside.  the outside of the tank is powder coated for evironmental corrosion resistance.

what i'd like to know is if there is any possibility of the coating breaking down over time when subjected to a 99.9% hydrogen environment. would the converted iron dihydrogen phosphate, or zinc dihydrogen phosphate, dissociate?

process temperature is maximum 50 degrees C.  pressures are as high as 500PSIG.  the tanks are made from mild steel.