Preventing Rear Fender Lip Rust?

[Monkeygrits]

Just has my wife's 09 mariner fixed. My buddy used POR 15, bedliner, and then paint. It was rusting on the little metal lip under the fender edge on the pass side. I didn't want it creeping around to the body. Has anyone found any way of preventing this? I know the the newer fords don't even have this lip. I'm guessing it's caused by getting chipped by a rock and then starting to rust. I was thinking about coating the edge with black RTV and sliding a piece of rubber edging over it maybe 1 inch wide to protect the paint.

[Terminated]

Keep it clean, if any rust starting, get it down to bare metal and coat it before it spreads. Seemed like a common issue with the Mariner/Escape.

[no1sirbutler]

Mainly rust in that area is caused by road dirt build up. Wash it regularly and actually spray the hose into the lip and spray until you see clean water come out. This alone will help prevent a lot of rust issues.

[Monkeygrits]

I make sure to wash up under there regularly but on both my mariner and my previous escape the surface rust started on the part of the lip facing the ground, near the inner edge, not up underneath. It's just a crappy design by Ford IMO. I know it adds rigidity to the panel but it sucks. Both started around 60k miles. If I can find a piece of edging I'm gonna try it. I figure the RTV will not only hold it in place, it will also keep water out. Thank god I don't have to run my mustang in this slop.