I had an interesting question arise today about aluminum stair nosings and concrete stairs. The structural engineer has some concerns about the aluminum being embedded in concrete. Obviously, these nosings are used frequently, and are manufactured for this purpose. Any concerns?
Well, the sulfates in concrete can attack the aluminum, but its typically just a minor etching. Aluminum is still preferred over steel because it wont swell as rust and cause spalling.
Thats all a total guess, but its sounds good 
Nope. We do it all the time, especially for photoilluminescent strips for high rises.
separate aluminum from concrete by coating with bituminous or epoxy paint will prolong aluminum integrity. I never allows aluminum, even if painted to touch concrete, aluminum will corrode.
Perhaps off subject, Brian who on your team specifies photoilluminescent strips? Which spec section?
for internal back of house stairs…no issues because …no moisture. no moisture=no pH therefore no etching. For exterior stairs separation is good. better yet no metal nosings. all of the metals expand and contract more than the concrete, all will corrode (you could use gold but …) and gold will expand too.
If you must use metal on exterior. I agree cast aluminum, a coat of epoxy, set it and forget it.
Exterior stairs: Cast iron abrasive nosings have stood the test of time. To some, they may not look “right”, but I think they’re great. I could show you a stair that’s 60 years old and the cast iron nosings are brown, but no more intrusive than a manhole cover.
Interior stairs: Aluminum is the choice with a protective coating on the underside.
I agree: Avoid metal nosings, but if necessary use cast iron on exterior and separated extruded aluminum at interior.
To answer Jerome’s question, I specify luminous strips & other egress accessories for stairways in high-rise buildings using MasterSpec’s Section 104513 “Photoluminescent Egress Path Markings.” You can get the Product MasterSpec version on Balco’s website: https://www.balcousa.com/technical-documents/
The New York City subway system mostly has used cast iron nosings on stairs, both exterior and interior, for many decades. I’ve also seen what appears to be cast nickel silver nosings on some stairs. I expect that cast aluminum would not hold up to the volume of traffic on their stairs.