Here is a good way to clean the rust with out taking the metal off, but please be careful electricity plus water...... not good. If your careful this works great.
Get a plastic tub; a stainless steel or iron (a scrap piece of stainless works fine)( The electrode wants to be large (within reason); if possible, larger than the object being cleaned. The iron electrode works best if it "surrounds" the object to be cleaned, since the cleaning is "line of sight" to a certain extent. An iron electrode will be eaten away with time. Stainless steel has the advantage (some alloys, but not all) in that it is not eaten away. I have had good success with sheet stainless salvaged from a paper towel dispenser. It has a large surface area and is easily shaped to fit the container.) electrode, water and washing soda (Arm & Hammer, for example) and a battery charger. About a tablespoon of soda to a gallon of water. If you have trouble locating the washing soda, others have reported success with baking soda. Also household lye will work just fine. It's a tad more nasty -- always wear eye protection and be sure to add the lye to the water (NOT water to lye!!!) The solution is weak, and is not harmful, though you might want to wear gloves. NOTE: It is the current that cleans, not the solution; nothing is gained by making a more concentrated solution -- DON'T!
THE POLARITY IS CRUCIAL!! The iron or stainless electrode is connected to the positive (red) terminal. The object being cleaned, to the negative(black). Submerge the object, making sure you have good contact, which can be difficult with heavily rusted objects. Get it backwards and your object will be relentlessly eaten away! Make connections on a part of your electrode that protrudes out of the solution, or your clamps will erode rapidly.
Turn on the power. If your charger has a meter, be sure some current is flowing. Again, on heavily rusted objects, good electrical contact may be hard to make-it is essential. Multi-part objects may not have good electrical connections between them. Fine bubbles will rise from the object when cleaning is in progress.
The time depends on the size of the object and of the iron electrode, and on the amount of rust. You will have to test the object by trying to wipe off the rust. If it is not completely clean, try again. Typical cleaning time for moderately rusted objects is a few hours. Heavily rusted objects can be left over night.
Rub the object under running water. A paper towel will help. For heavily rusted objects, a plastic pot scrubber can be used, carefully. Depending on the amount of original rust, you may have to re-treat. The amount of mechanical action will depend on the fragility of the object. Use your discretion
The clean object will acquire surface rust very quickly, so wipe it dry and dry further in a warm oven or with a hair dryer/heat gun. You may want to apply a light oil or a coat of wax to prevent further rusting.
