Originally Posted by Nagrom_

As per the late and great Sheldon Brown:

Stiffness

Stiffness affects the riding qualities of a bike frame, since a frame suffers no permanent deformation in normal riding.
Stiffness is determined by a property of the material called "elastic modulus" Elastic modulus is essentially independent of the quality or alloying elements in a given metal. All kinds of steel, for instance have basically the same elastic modulus.

Originally Posted by Nagrom_

and regarding how they weather, its steel, so it will rust if you don't take care of it.

Wipe it down when it needs it, frame saver on the inside would be a plus, when the clear coat wears down give it another.