What's in Cor-Ten?

It is a steel that contains copper. This improves the adherence of the rust to the surface. This provides some corrosion resistance. Applications need to be controled. Don't use it where it will get rubbed, such as a hand rail. Don't use it in a buried or partially buried application. To work well it needs to be able to drain and dry. The splash zone in marine use ought to be terrible for this material.

Dan: Go to Rautaruukki Steel's web site at

click on Products and Services, and on the left click on Brochures and Publications, and under Hot Rolled Strip and Plate products, click on Weathering Structural steels. This will download a big Acrobat file (1.86 Mb). See Table 4 for compositions (Cu-Cr-Ni).

Pittsburgh Pete

Be carefull if specifying weathering steels, they are excellent in the right application but some applications are not suitable.

Brochures

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David: You are correct, design must be done carefully, and sea coasts are not suitable places for conventional weathering steels. (Recently the Japanese have made some 3% Ni seacost weathering steels though).

For older US experience on bridges, see the FHWA TECHNICAL ADVISORY : UNCOATED WEATHERING STEEL IN STRUCTURES T 5140.22, October 3, 1989

Pittsburgh Pete

Thanks to all you guys, for those answers (especially the first one). Dan Shanefield