Evaporust and oxalid acid are two different methods. The Evaporust is quite expensive at around $40 a gallon. It works by chelating the iron. Essentially on a molecular level the iron is absorbed in the liquid, up to a 1/2 lb per gallon. The oxalic essentially dissolves the rust plus maybe a bit of metal, not much since the PH isn’t too low. Both are quite effective. Evaporust especially is great for soaking small parts. Evaporust is much slower acting but less damaging to the paints it appears.