We make small parts for industry, we are a small mom-n-pop CNC shop, Most of our parts used to be stainless, and we still make a lot of stainless parts, but now a good percentage of our parts are carbon steel.
Rust on our parts is death, even rust down deep in tapped holes, it acnnot be tolerated.
My first inclination, years ago, was to soak slightly rusted parts in Ospho, dilute phosphoric acid, then rinse them off in water, and dry them in the oven and oil them.
A few years ago I came to the conclusion that the oven is the "perfect storm". Oxidation always occurs faster at elevated temperatures, and especially when the humidity is high. The oven provides both conditions.
We currently dry parts with air blast, the oven would be fine if it were provided with an inert atmosphere, like nitrogen. The concept of driving all moisture out and replacing it with oil is sound, but adding heat and moisture simultaneously is a disaster.