Painting Over Rusted Bolts on Gutter

Usually a rusted ferrule or joint in a galvanized gutter can be simply painted with a good primer, then top-coated with finish paint. Remove as much surface rust as possible by sanding the rusted spot with emery or sandpaper. You could also replace the ferrule with a new galvanized or aluminum one. Note, do not mix metals. If the gutters are aluminum, use aluminum fasteners, and vice versa.

I have used 100% acrylic stain blocking primer in this application and had good luck. If you spray paint, be sure to use something to cover the roof for at least 3 feet above the gutter, and an overspray flash panel, or you will color the roof as well. I like using a roll of builders paper for this purpose if the pitch is not so steep the paper just slides off.

Use a wire brush to remove the rust and then prime with a rust resistant metal primer and apply your finsih paint. I would not spray the gutters as it seems like to much trouble to cover up. You could have half it done with a brush by the time you cover up the roof.