Yeah, eventyally they will rust out starting from the edges and continuing to the backside.
They DO make a rocker-shootz clear rubberized spray you can put on. Also called Rocker Guard. Clear urethane rubberized coating similar to what a bodyshop would use.
HERE. 3M makes a more Pro version but the Dupli-Color sould work fine. I would mask off, do the prep. Then spray some acetone on the paint with a spray gun (to soften the original paint below). One wet coat of acetone spray ...then let it sit a minute to evaporate and immediately spray on the rocker protector. You want a 'chemical bond' ... so softening will allow the rubberized coating to 'bite' or 'melt-in' a bit to the trucks original clearcoat.
But if you just use regular motor oil out of a squirt gun or ZoomSpout (look it up), under or behind your truck's panels, and keep doing it every few yrs (or use any of the lanolin-based oils) ...that alone will keep panels from rotting.
Box. And while you're at it, do the same with your trucks bed wheel arches. Shoot oil up through the gap in front of the rear tires. And the rear area by the rear bumper. Also the lower front. Over the wheel arches it's a good idea to pick the rocks and sand out from the wheel arches (inside) before doing the oiling. But that requires WORK. Making a tool to pick rocks out which get lodge up there. I got a good two handfulls of rocks and debris out of each of my truck's wheel arches. Then I washed out real well on a dry summer day. After a couple days of drying I then oiled the arches. AND ...you need to put some oil on the wheel lip too (the part nearest the wheel). So oil can get whicked 'up' between where the two pieces of metal are spot welded. WHY? B'c Dodge used a sealer about 1/4" up from the wheel lip. So any oil you get up there from the backside WON'T make it through to the lower lip. SO you MUST put some oil on the lower lip to suck-in (capillary action) . Do it a few times repeatedly ......and that will prevent your box wheel lip from rusting.
Tailgate - Inside ...and frontside of lower lip.
Lower front fender area
Frame! These are box frames and will definitely rot out. Squirt oil in them. The oil will migrate and will prevent rusting. Go to the junk yard and check the frames of those early box-frame trucks. That's what yours will look like in xyz number of years if you don't protect it. Re-do every 3-4 years.
Hemi badge! It would behoove you to remove your truck's front fenders and scrape away the sound deadener on the backside of the hemi badge. Or you WILL have a hole right in the middle of the front fender there after a few yrs. My neighbor's '13 has a big rust hole there you could stick your arm through ...where the badge was!! Once you remove the sound deadener patch, put a gob of grease where the adhesive was. Seriously. Don't wait. Your truck is 11 years old ...so do it this summer before there's a rust hole. While you have your FF's off, you can easily re-do any suspension or manifold work you have been thinking about doing. More than likely your lower ball joints are weak (if they're original). Easy to press new ones in with a free-rented (parts store) press.
Good luck!!
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Do all those things and the top of the gas tank support frame and your truck will look great for many more yrs while other '15's are rotted away ...in your area!
