After doing a faceplant on pavement wearing a nice pair of Carrera metal frames, I made the switch to plastic frames. Mine are made by Liberty from Lenscrafters. The old metal frames cut a chunk out of my face and left a deep scratch 1/4" from my eyeball. I haven't pavement tested the plastic frames, but they have to be better than metal vs. skin. Back when I did wear metal frames, never saw any corrosion problems, and I'm a heavy sweater (?).
The zip tie in the picture was temporary due to a broken mirror support.