For rust removal I prefer soaking in Evapo-Rust. This will remove rust from places that might be difficult to sand especially if you're dealing spots that are pitted.

I've got a post in my Tandy 1000 TL restoration thread where I show the process, and before and after pics: Re: Tandy 1000 TL Build / Restoration

For coating and rust protection, one option is galvanizing sprays (e.g. zinc spray) as an alternative to regular paint.

Thanks for sharing those nice pictures!

I had experience myself with citric acid (a very good alternative to evapo-rust) for some Macintosh cases. It works like wonder. But this is chromed? surfaces, most of the rust is not exposed. On those yellow-looking macintosh frames, the lemon juice removed the "yellow" coating as well, leaving bare metal which would rust by just rinse it. As you said, I did use galvanising spray afterwards, the result was brilliant. For a case like yours, it's my favourite process too.

Here is my process with the Macintosh: https://youtu.be/crMj03OQlhQ

But this frame is almost glossy so I'd like something similar to replace the coating with.

Now, the PS/2 floppy had some similar corrosion inside and I sanded it with a wire wheel. What I found was that there was no "coating" coming off. I'm not sure what the process was but in the end I just applied a thin layer of oil and happy days - though you can still see where the metal was eaten away from the rust.

I think I'll start with some scrubbing and rust removal. If that works, happy days. If not, I'll prime and re-paint.

Thanks for now!

The rust damage was way too much so it will need a coat of paint.

I had to use a abrasive rubber bit to crack open the little blisters which were hiding rust. A night in citric acid and A LOT of scrubbing and sanding got rid of the rest.

Now it will be primer, then paint. Looking for a suitable paint now.