Amar, they've been using aluminum for a looooong time on wheels. "Alloy" wheels almost always carries an unspoken "Aluminum" before it. Bare steel wheels wouldn't last long unless they were stainless, which, while I've never seen it I can't say it doesn't exist. Man, would that be something to see - mirror polished stainless wheels!

If they're really not painted - do you have a picture of these wheels? I know nothing of the Sirius rim - then I'd spray them down with some concrete cleaner from the hardware store. It's a strong acid - or mixture of such - that will eat away oxidation and etch the surface, leaving an excellent surface for primer to adhere to.

Wash in lots of water, maybe with a little baking soda to neutralize all the acid. Then prime, paint.

If they ARE painted, or even clear coated, 20+ year old enamels can be tough as nails, I'd use paint stripper of some sort first. Well, only if you're trying to fix damage, otherwise I'd do some light sanding and paint right over the factory finish - if the primer/paint has stayed on the wheel for this long, it ain't gonna come off now and paint provides a better substrate for more paint than bare metal does.
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Sean - now frolicking in the Land of a Thousand 240's (aka, Fredericksburg) thrice a week.