There may be a build-up of muck around the inner wheel arch lip. Remove any plastic liners and clean it back.
With abrasive, remove all existing coatings.
Remove pitted corrosion with deox GEL. This may need repeat application and make sure work is carried out over 10 degrees C as it will be too cold to work otherwise.
Prime the cleaned back steel with electrox then topcoat to finish.
It would be worth coating behind the liner with dynax S50 wax after the repair is carried out.