Hopefully you guys can see it. It’s a lot worse now. Where the front fender meets the skirt. It was there before the mudflaps and it’s grown slightly ever since I took them off. Would it be cheaper to replace the whole front fender panel and possibly repaint or get it repaired? Also does anyone know the part number for the passenger front fender panel. The car is a 07 STI. Thanks.

 

Like a bad rash 😂

 

Just done mine plus rear arches, front bumper ,sills, cheaper to refresh old panels.
Mine is 06 ,2 years ago seen no rust there ,look like Yours 1y ago than worst.
Its common on 15-16 years old newage , rust starts on sills getting to front wings, worst on the rear sills part ,arches sometimes even on rear turrets.
For example easy to notice on wrx without arch extensions.
Think Yours front and rear part of sills could need job to.
New wings costs over 250 quid plus paint. Do it now, till You have surface rust without holes.

 

So much mud and crud collects in that area of the front wings.
If it was me, I'd take it to a decent local bodyshop, small repair on the wing. White is probably pretty easy to match in a small area, and they can repair / blow it in.

Maybe you could ask them to remove the inner arch liner on the other side and clear out all the debris in the hope it doesn't happen on the passenger side.

 

I'd remove the side skirts and inspect the sills too while at it.
Perhaps the car had a replacement non-genuine wing at some point in its life?
I see some blistering on the side of the wing which isn't "normal" unless the car has 100k+ miles and hasn't been washed regularly after being driven on gritted roads.

 

When I removed my side skirts and the front wheel arch liner, the mud collected at the front of the sills was alarming…proper full of mud and damp which caused surface rust but it never broke through so I got it in time…will find a picture of where to check

 

If the fronts are rusty, so are the rear of the sills. There's a bigger mud trap there.
Just had my 08 done. New rear ends to both sills and sprayed to blend in. My car's a keeper so the problem was convincing the body shop I didn't just want an MOT repair. It cost more but I'm really happy with it.

 

When i wash my foz , i now wash inside the arches front and rear , including the bottom part of the arches , plus the rear sills have had dinitrol
sprayed in and on them , just to slow the process down a bit , it’s surprising when you wash your arches how much crap can come out of them 👍😁