Rust on steel firearm parts.

First you wet with lemon juice and put some salt( sodium chloride) over the rusted parts. Use a used tooth brush, brushing over the spots. Use water to rinse away the rust. You may have to repeat the actions in order to completely remove the rust. Metal will not be oxidized when no moisture and oxygen so you can wipe the firearm parts dry and coated them with some kind of polishing oil and keep them in a tightly sealed container with some silca gel to remove moisture.