I have 2 cream separators, both have rust where the tinning has worn away over the decades. Has anyone ever had anything retinned or perhaps powder coated successfully? Has anyone ever come up with another solution?

Powder coating is successful ONLY if the old lead solder is removed and it is welded back together. Retinning is plausible, but I have not done it personally. Chroming is not food grade. Powder coating is the best option if you can redo the tinware correctly. If the centrifuge is rusty, well, I don't know what to do about that. I haven't heard of anyone retinning it successfully, but if someone did that would be great!

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The parts I'm mainly concerned with are the discs and bowl, what you call the centrifuge. Found a place that retins but it's $5.00 an inch!!! I can buy a brand new, smaller separator for what it would cost me. I'm thinking either live with it or enamel paint.

Powder coat won't stick to lead alloys?

You could paint it, but it will not be food grade.
Powder coating will stick to lead and lead alloys, but they melt in the powder coaters' ovens.
There is a retinning place in Chicago, I believe, that one person said was very reasonable. Perhaps you should try checking in Chicago?

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Ah! I didn't realize they got up that hot. Huh. I'll see if I can find anything in Chicago.

They make FDA food grade paints. Epoxys I'm told. Any opinion?

Let me know if you find any that are actually food grade. If you order a powder coating, you have to make sure it's approved for continuous food contact. Some are only approved for accidental food contact. All of the paints that I've found have only been rated for accidental use, and cannot be used for something like a separator with continuous contact.
Hope this helps!

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I'll keep looking. The FDA approved Food Grade paints can't be shipped to NY for some reason. ??? Got me. I don't know how much the bare metal would taint the milk. My DeLaval is in lots worse shape than my American Separator. Maybe I'll just stick with the old manual American and forget the electric DeLaval. It's a shame because I just had the motor rebuilt and the electrical shop guy was tickled because it was so old. He figured the 1920's. Still works great.