240 90 245 Wheel Arch - Early signs of rust

The back left is showing (5 on a 10 scale) signs of rust. It looks flaky if that makes sense. What do I do? It feels a bit like picking a scab.

On the edge or the lip or behind underneath the panel ? Any pics? Are you going to have the repaired part painted? Too many variables. The easiest and perhaps longest lasting without replacing any metal would be to grind/ sand down to bare metal and skim coat with short strand fiberglass. Then top coat with body filler and go on from there. Others will have a different approach. This is why a pic is helpful.

Grind it down smooth, then do what he suggests, and it should be ok. One thing, when you do wash the car, put a latex or nitrile glove on, and clean the back of the wheel arches out. I had a '73 145 that had much worse rust in that area. Car never saw road salt, instead having a 1" thick layer of mud caked on the inside of the wheel arch. Previous owners never cleaned it out.

-J

What am I grinding it with?