That looks good. I have been through much the same thing with wrought iron patio furniture when I lived back in Chicago. The problem is the rust will always reappear in a short time. It's very important to get all of the rust out as deeply into the corners as possible. The only acceptable way I've found to do this, to where any type of repaint job will last, is to sand or bead blast the affected area.
I purchased one of those portable sand blasters from Harbor Freight.
20 lb. Pressurized Abrasive Blaster
They require a air compressor. If you don't have one, you can rent them from places like Lowe's or Home Depot very reasonably for a few hours. It's the only way to properly remove the rust from deep into the joint. Then when you prime and paint you are painting virgin metal.
Even with that type of treatment the rust will reoccur, because the conditions that allowed it to form in the first place are still there. I had a friend who's pickup was afflicted with this same problem. He was very anal about not tolerating any rust on his vehicles. What he ended up doing was after he abrasive blasted all of the rust out, he went and had all of the open joints Tig Welded so no moisture could enter the joints.
He then primed and painted the hitch and that did the trick. But that's a lot of time and work. But it held up for years in the rain, snow, salt, environment in Chicago. I had a much better solution.... I moved to Arizona!