In addition to Ed's excellent explanation, Cor-Ten was also used briefly is boat building. Specifically, for rescue craft for the
British Life Boat service. What was found was that it was hard to work and resisted shape forming as well as it had very poor
fatigue resistance.Continuous flexing caused plate fracture. This would not be a good thing if used in truck frames. It is still
used in building construction for external appearance and statues.
Steve

"engineman" wrote in message ...
On a recent episode of "factory made" on the manufacture of light rail
cars they mentioned that the frames were made of what they called
"weathering steel" which was described as an alloy which only develop
surface rust which prevents further rusting.
If there is such a thing, I'm wondering why they don't use it on
automobile frames?
What advantages would it have over galvanized steel?

Engineman