ASTM A588 Grade A corrosion resistant steel is a weather resistant steel which could more accurately be termed as an "Atmospheric Corrosion Resistant Steel".
It is a copper chromium alloy steel – this alloy displays a greater level of resistance to atmospheric weathering when compared to other unalloyed steels. Its chemical composition promotes the early formation of an adhering protective layer of rust when exposed to the elements.
A588 Grade A
Weather resistant structural steel ASTM A242 A588 Corten Steel plate