Tim:

Corten steel was a proprietary trade mark of US Steel. This was a speciality steel which was self protecting in that in rusting it formed a skin of iron oxide that bonded with the surface of the steel and sealed it preventing further rusting. The first use of Cor-Ten steel in a freight car was by the B&O in 1934. Cor-ten is a high strength steel and allowed the construction of cars with approximately 8% less weight from the steel components. The debate is does the weight savings warrant the significant increase in the cost of construction.

Rich Orr