There's another safe and simple way to selectively remove rust from ferrous parts - that's using electrolysis. All you need is a plastic bucket, a battery charger and washing soda (not baking soda). I have removed rust from scientific instruments this way without any abrasion, surface removal or any damage to non-rusted areas.

Google "electrolytic rust removal" and you'll find a lot of detailed instructions.

But a word of caution- it will remove all oxides including blueing.