How do you  loosen rusted nut?
 Brush off Loosen as much rust as possible off the nut with a wire brush.Tap the sides of the nut with a hammer to help the rust separate and fall off.Apply heat Apply heat to the side of the nut for about a minute.A small, narrowly directed propane torch—one made especially for small jobs—will work best for this job, but be careful.Spray lubricant When the bolt is cool enough to touch, spray WD-40 on and around the nut and bolt.Tap the end of the bolt with a hammer to loosen the threads and allow the oil to penetrate.Loosen Wait another minute or so for the oil to work, and then use your wrench to loosen. 