Wheel well surface rust

[Lotto]

So i have a good bit of surface rust in my wheel well. I got a wire brush attachment and got all the rust out but there is still a good bit of the black kinda rubbery anti rust stuff in the wheel well. Not sure if its stock or of someone sprayed the black stuff on there. My question is, should i wire brush the whole thing to clean bare metal, or just get out the rust and spray rust blocker?

Thanks.

[breadbox]

I'd keep going and get a good amount around where the rust was and then spray POR15 and some undercoating.

[pj]

wire brush it or use a wire bit on a dremel or a drill, get it clean and paint it over with some thick rust resis paint.
check all the seams as well, dont be like me...dismiss surface rust around a seam then get curious if the seams bad and poke it...i acidentally put my hand through the wheel well...it didnt look bad at all, almost unnoticable...but inbetween the layers of metal...and the seam it was done for. so take your time and fix it right.

[costa_rican13]

Breadbox where can I get por15? I plan on taking my splash guards out to go low low on my coils but I wanna redo the under coating. I already have 5 cans of the rustoleum under coating stuff.