sounds like you have no finish left of these parts that are rusting. If that's the case you need to get it reparkerized(that was the original finish).
I just got through de-rusting 5 Korean Imports that were rusted beyond belief.
I blasted them, degrased and into the park tanks. Parkerizing is a phosphate finish, I use manganese phosphate as it comes out a black color that was like the original GI finish
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