Yeah I think a couple cans of Rust-o-leum is a better alternative and should be just fine... Linseed Oil is a stopgap measure for inside frames as BioTex said.
1985 CJ7 Project
Phase One :
5.3L Vortec/4L60E, Moser axles for AMC20, Twin Stick'd Dana300 - Completed
Bedliner, Rollcage, Seats, BESRK Rear Bumper w/ tire swing, Soft Top, and a few other goodies - Mostly Complete
Waggy 44 front, Scout D44 Rear, 4.56's, ARB's (F/R) SOA with YJ Springs, 35x12.50x15 BFG MT - Not Even Close to beginning
Also a mostly rust-free 1970 Scout 800A That I'll get to start working on someday...
Chrome won't get you home...BUT Rattle Can Black may just get you back"