Phosphuric acid, sold under the name Ospho at home depot, lowes, ect in the paint section will neautralize and kill any rust on any metal material excluding aluminum which it will literally eat, not that it rusts. About $5.00 a quart and a quart will last a very long time, one of the best product I have ever used. It also acts as a primer after its applied and has dried, just hit it with a wire brush and paint, or you can leave it alone. I personally like the look of it after it has dried. Here's a pic on the base of a sculpture that I made that was eaten up with rust.