If you work with machines or in construction long enough, there's a good chance you will encounter rusty nuts or bolts from time to time. Sometimes you can remove them using a little elbow grease, but often they require a little more effort. When rust begins to accumulate on a nut or bolt, it actually causes it to swell beyond its original shape, which can compromise structural integrity. If you don't use the proper methods, you may end up breaking the bolt and having to cut it or drill the bolt out.
Put on your gloves to prevent any flakes of rust from cutting you. Brush the nut and surrounding area with the wire brush. The more surface rust you brush away, the less you will have holding the nut in place.
Place the proper bit on the socket wrench and attempt to turn the nut. If the bit slips on the nut, it's a good sign the nut has corroded. If that is the case, move down to the next smallest size metric bit. Having both standard and metric bits will ensure that you have the right size bit without being too big or too small for the nut. If the nut doesn't turn, continue to Step 3.
Apply a good amount of liquid thread loosener to the nut and surrounding area. Products such as WD-40 and Liquid Wrench both lubricate the threads and break up existing rust. The key to using these products is patience. For a severely rusted nut, it is best to leave the thread loosener on for at least 24 hours. This gives the loosener enough time to penetrate the rust.
Increase your leverage. If you cannot turn the nut with your socket wrench, a breaker bar gives you increased leverage through the use of a longer handle. For a larger nut, further increase the leverage by inserting a section of metal pipe over the breaker bar handle.
Heat can help loosen a nut as well. The proper application of an oxyacetylene torch or hand-held propane torch can expand both the nut and bolt. Once it cools, the metal will contract and, if you are lucky, the nut will come off relatively easily. If you are unable to remove the nut after following all of the steps listed, look for a tool known as a nut splitter, which will cut the nut in half while preserving the threads of the bolt. Always remember this phrase: "Righty-tighty, lefty-loosey."
Never use heat on a bolt that has been covered with a liquid thread loosener without wiping the thread loosener off first. Failure to do so can result in a fire.