I would propose the following procedure:
1. Bath the object in a large enough container with Aceton for a few weeks. Change the Aceton from time to time. This will wash out corrosive salts. The object should be completely covered with Aceton and should not lie directly on the ground. Alternatively you can take distilled water.
2. Heat the object in an oven so that it is absolutely dry.
3. Remove loose particles carefully (!) with sandpaper. They will drop off anyway.
4. Clean the object with a Dremel and steel brush. This will not affect the patina, but will remove the rust. Put on a face mask and be careful to not step into the bristles that will fall on the ground.
5. Brush the object with heated paraffin wax.
6. Keep it in dry environment below an air humidity of 50%, for example by putting it in a container (or showcase) with silica gel (the orange ones, not the blue).
That's what I have done with iron objects, but in the end, the corrosion is unpredictable. Some objects stay rust-free for decades, others will fall apart in a few years, no matter how you treat them.
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