Mary,

You would me MUCH better off with stainless (rather than galvanized) angle
and hardware if you can get s/s in adequate size.  I am not aware of
compatibility problems with regular and galvanized.  However, any non-galv
should be painted and flashed (don't forget the end dams and drip edge) to
death.  Also make sure your shelf L's run at a continuous elevation all
around the building, or else put in vertical (as well as horiz) soft joints
to isolate panels of masonry and permit them to move independently without
cracking between offset shelf angles.

Ralph