I would like to put in my 2 cents!
I have done alot of powdercoating on stock and custom motocycles/parts for some time now, as I hate chrome!
I beleive the advice here from both party's 180 And 32krazy to be completely correct and totaly debatable! (and for the record 180 I can't spell for a s@#**&t) I have personally done this both ways and have not had great success with aluminium products after sandblasting chrome off, but agree that it is the best way to achive total adhesion to the part. I have had better results with just a very light sandblast and not trying to remove the chrome but rather dulling it, as we have also had peices of chrome peel off and that becomes a real mess! I have also gotten away with red scotch brite pads, (use this method exclusivly now) as stated I am only trying to dull the chrome to allow a better surface for the powder to stick to or you take the chance of it peeling off that shiny crap.
I have had no powder come off of any parts but I am always real careful and only wash by hand, also remember wheels take alot of abuse and I would caution ever going through a car wash or using a presure washer.
If it was me I do not think I would powdecoat a set of chrome wheels as there is a better chance to reuin them now or later. 32krazy is right you would be taking a big chance and in the end it is a hack job, I think if they were not already chrome you would be fine with powder.
Well good, bad or indifferant that is my experianced 2 (canadian) cents
Angelo -V2addict