I am replacing the front frame rail extensions. My oriiginals were beat up bad so i ordered a pair of new ones. These appear to be steel and have already got some surface rust. Should I paint these the same black as the engine compartment. Krylon/?
I'd paint the insides with weld through primer (has lots of Zinc to protect against corrosion), and paint the outside with POR15 (It's Really tough stuff). After a while the shine on the POR15 will fade and look like everything else down there. But if you want a semi gloss, you can give the POR a topcoat of primer when it's still tacky to the touch, then hit it with Krylon after all is dry.