[Targalid]

I would remove the visible rust with a Scotchbrite pad, then apply Naval Jelly (available at local auto parts store) to remove the remaining rust. Naval jelly contains phosphoric acid which converts the metal to a less rustable surface. It may take more than one application to remove the rust. When you are satisfied that all rust is gone, rinse away any invisible naval jelly with sodium bicarbonate solution (make it yourself from baking soda and water). After the surface is dry, paint it to prevent air/moisture causing future corrosion. My local windshield place uses polyurethane windshield adhesive between the gasket and the metal to prevent future water entry.