Fiesta mk7 rusting arch

[joeyhoush]

Hi guys, first post on here but have been snooping on the forums for a while now. 

 

So basically I bought a mk7 Fiesta Zetec S last week and upon giving it its first wash I noticed the rear wheel arch has started to rust from what looks like a bad respray job from a previous scratch as you can still see the primer underneath! Firstly I am disappointed with myself for not noticing this when I originally inspected the car before purchase! 

But anyway, I am now wondering if anybody can suggest the best way to tackle this? Are there any products/techniques out there that will do a good enough job to get rid of the rust and protect the paint aswell as hide the primer or will it be a case of saving up for a respray? 

Any help is appreciated as like I say I am a newbie here!