Or maybe get them de-chromed from a plater or sandblaster and paint them grey with black quadrants like the factory

I'm facing the same issue. I have some Pfitzner chrome steel Cooper S rims that I bought in the mid 1970s. They're 7 x 10 inch they were made with a spun half, meaning there is only one weld (i.e. not widened by banding as was common back then). They're a bit rusty and pitted now so really need re-chroming. "Chromies" as they were called were very popular in those days as there wasn't the range of alloy wheels there are now. On an all black car wide chromies looked sensational when new.

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1965 Mini Van (1360)
1970 Mk2 Cooper S (1310)
1978 Rover SD1 V8 (4.6)
1996 Land Rover Discovery V8 (4.0)

quote]can I ask why it needs to be separated?

I have a set of chromed S wheels that look like they were done in one piece[/quote

The preparation prior to Chrome plating is all important, the surface must be smooth,( note polishing after plating these days is almost never required) as any pitting you can see prior to plating will be even more evident when plated, to achieve this smooth surface it has to be polished, this for the most part is done on a polishing lathe. that looks a bit like a giant bench grinder with long spindles, it is almost impossible to polish the inside of the rim and the centre when they are assembled, even if you could get a very smooth surface. you now have to electroplate the wheel assembled together, the next part of the process is extremely important the surface has to be cleaned with a range of chemicals both acids and alkalis. then comes the electroplating part, some times but not always it is copper plated first, then nickel plated then chrome plated, in most cases all these plating solutions are acid. cooper plating from memory is 100% efficient this means that 100% of the current applied to the cathode will deposit metal Nickel Plating from memory is around 60% and chrome once again from memory is around 10%. if you use nickel plating as an example then
40% of the current does not deposit metal but it does cause gas to be liberated.
all this has to a lot to do with the thickness of the metal deposited, in what is called low current density areas the amount of metal deposited is reduced further, so to get good coverage down in the crevices and around holes Etc it is very difficult, also where the centre is welded to the rim between these surfaces there is no metal deposited at all and often acid or acid crystals are caught in this area which promotes corrosion at a later date

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