Aluminum mounted on Steel

[JimmyD123]

Roof top air handling unit with an aluminum channel base resting on an all steel roof frame. The base will be mounted w/ S.S. bolts, the roof steel is hot dipped galvanized. Does there need to be a barrier between the steel and aluminum, and suggestions as to what type of barrier to use if needed?
Thanks

 

[XR250]

I have seen contractors use peel-and-stick rubber flashing for a barrier. SS bolts are probably your best bet but can still have a galvanic reaction.