Zinc spray?

You could try electro plating? It would be a bit of an outlay (and it's a messy, involved process), but gives the best quality finish compared to paint, spray, etc.

I've been meaning to pick up a kit to do some electro plating of various vintage car components, nuts, bolts & fasteners etc.

Zinc spray: very interesting! I cannot figure out what the finishing is going to be and whether it lays a non-conductive layer but I guess I could give it a go. It seems to be the best solution for those internal parts.

Electro plating is for sure the best solution but as you say, messy and large project!

evaporust or blaster metal rescue (same thing) and a light coat of oil. keep away from excessive moisture.

One some old Macintosh metalwork I had GREAT success with citric acid - not from lemon juice, I have a can from ebay to clean my kettle!
The rust disappeared but the yellow coating disappeared too. I have some paint coming but I think that for those internal parts keeping the bare metal would be good.

Would oil last for a long time though?

I tried the zinc spray and it seems promising. Not the plain finish I'd like but it seems to be conductive. I think it's good for internal parts.

Great! If you apply enough thin layers you should be able to polish if with a cloth to get a shinier finish.

It seems as the acid aproach are second best to give the metal parts a new coating by electro. I believe the metal parts are originally coated by nikkel in the factory, by the use of electro.

I quit using any acids for rust removal, and always use Evaporust. It does a great job of removing rust, but doesn't eat the metal. It also gives the metal surface a dull greyish color if you leave it on for half a day or longer.

interesting. It's a chelating process. "Rust-Block" is also very interesting but too bad it only lasts 1 year.

To be fair, citric acid didn't seem to be extremely corrosive on my parts and worked effectively. It's citric acid so not so dangerous I guess. I had a dull finish indeed but the parts would rust VERY easily if a drop of water was left on them.

@brostenen yes, those are nickel coated. My acid removed that too.
@Doornkaat cool, I'll definitely give that a go, thanks!

"Rust-Block" (...) only lasts 1 year.

That seems to be automotive stuff, so they probably mean one year of straight up exposure to the elements? Should be fine for much longer on things only used indoors.

I have a feeling that that is for short terms protection, while you sort out some coating.

The description says "When you are ready to remove the invisible coating, simply rinse it away with warm water. Then, your item is ready to paint, primer or oil".

the evaporust/metal rescue "rust block" will last a matter of days; possibly longer in a humidity stable environment. 'the must for rust' has a more durable residue, but that is a phosphoric acid product. you'll need to coat with a light oil or grease.

Even "Must for Rust" says "12 months protection". I guess it's how physics works, not surprised.