cor-ten sheet supplier on the west coast?

Short answer- there arent any.

Corten is expensive, specialised, and comes in only a few sizes. Nobody much stocks it. Only one company, USS, makes it. Its also a pain to work- most any weld bead shows up ugly, as in different alloy, different color, and you need to sandblast the whole thing after fabbing but before use, so it all starts out rusting from a clean start. Then, if it ever gets scratched or tagged, you have to sandblast all over again. Plus, it bleeds rust when it rains, staining concrete and surfaces below it. Architects, most of whom know nothing about making things, love it, and spec it all the time, then cant figure out why its so expensive to have fabricated.

Try these guys.

Blackout wrote:

Cor-ten is a tradename for USS's family of weathering steels. A242 and A588 are the ASTM specs that cover these steels. You'll get more hits searching for A242, A588, and "weathering steel" in various combinations. For example...

I expect the biggest problem may be getting small quantities of the stuff, especially in light gages. Someone here in ME has been making Cor-ten bells from what I'd guess is 10 or 12ga for many years, so it is available.