Removing a rusted nut is a lot like removing a rusted bolt, except that in many cases you want to save the bolt that the nut is attached to. It may be of a particular size or strength that is hard to replace, or the nut might be on a stud, the bottom of which is implanted in an engine block and which replacement of becomes a very difficult and frustrating proposition.

Removing rusted nuts and bolts is a frustrating proposition from the get go, but there are a few things you can do to make the job go a little easier.

If you know a little bit in advance when you are going to have to tackle a rusted nut, you can sometimes spray a penetrating oil such as Liquid Wrench on it for a couple of days in advance. While this product is an old standby, there are a few new ones on the market which also are very good at penetrating the corrosion binding the seized nut. If you have the patience to let these chemicals work for you, you may find your corroded nut comes off much more easily than you anticipated. There are a variety of penetrating oils available at any automotive parts store.

It helps to take a wire brush and clean off the threads of the bolt that you want the nut to wind off. You are fighting the friction of the rust between the nut and the bolt, in the threads directly under the frozen nut. Once you break that connection you are on your way to being home free, but many a time you can get the nut to start turning only to have the shaft of the bolt break because the load of rust on the threads between the starting point and the end bind again, and you overpower the shaft strength. Hence, clean your threads.

Beyond penetrating oil, you also have the option to heat the nut with a propane ot Mapp gas torch, and as with a bolt in the engine block, the differential in heating and cooling rates may cause the nut to break free. Vibration also is helpfull, but you have to be careful if you are beating the nut or bolt with a hammer as you don't want to destroy the threads.

If you are working on a larger nut, such as is found on parts of the suspension, and you can't make the nut come loose, there is a tool called a nut splitter that you can sometimes use. If you have the room you can use this to break the nut into two pieces and frequently not damage the threads. On smaller nuts sometimes you can get a small hacksaw at them or you can get a cutting wheel on a Dremel tool in to cut the nut off. The little wire wheels that come with Dremel tools are good for cleaning threads in tight places as well.

When attempting to do a job like this it is important to use a good quality wrench or socket if youo are using a socket wrench, as many inexpensive socket sets and wrenches are not made of appropriately hardened steel and/or they may also not be well machined. The result is that because of a poor fit the wrench turns on the nut, simply rounding off the corners, making the job of getting a good grip on it much more difficult.

It can be tempting when you are faced with using an SAE (Society of Automotive Engineers) set of wrenches on an imported car, or a set of Metric wrenches on an American car, to use a socket or wrench that is "almost" the right size. You may get away with this if the nut or bolt turns easily, but if you are working on one that is rusted in place, you may create much aggravation for yourself by turning the corners off the nut.

As a side note, one of the interesting things I have discovered as a backyard mechanic is that you can no longer have just one set of wrenches, SAE or Metric, as many "American" cars are made using components with Metric sizes. My first experience with this was with a 1989 Ford Country Squire station wagon, an automotive icon of another period, but the nuts and bolts holding the power window motors in were all set using metric sizes.