Alro stocks ASTM A606 Corten sheet, a High Strength Low Alloy (HSLA) steel sheet. This unique product is 20-30% lighter than carbon steel and exhibits up to four times the atmospheric corrosion resistance of common structural carbon steel. A606 typically arrives without rust but as it is exposed to external conditions, the steel develops a weathered orange-brown oxide that is resistant to corrosion, increasing its life and durability, and does not require painting. It is weldable, formable, punchable, and machinable using the proper techniques.
Originally COR-TEN® was a steel material owned by U.S. Steel. This product has lived on as A606-4 steel or A588 finish. COR-TEN® was an alloy that was specifically designed to form a stable rust-like surface appearance that would not require painting. The dark brown oxidation that coats the steel does not allow for deeper penetration of wet weather such as rain, snow, ice, fog etc. Testing in laboratories has essentially shown that the alloying elements in the steel clog the pores of the steel surface and this results in protecting the inner steel.
It should be noted that A606 is not recommended for use in areas with extremely high rainfall or a high content of salt in the air, persistent fog or extremely high humidity. It should also be noted that runoff from this product may cause rust stains.