I've sent hundreds of parts to be powdercoated this year, steel and aluminum. We don't blast them, just clean and ship. Much of it fresh off the mill or lathe and very shiny. Some is clear anodized extruded aluminum. A powdercoater who knows what he's doing won't have a problem with polished aluminum rims. If there's a clearcoat that would crinkle up in his oven, pretty obvious problem then.
Today I've been taking off powdercoat with a scotch disk on a die grinder, this stuff is pretty tough. I get a lot of aluminum hard anodized, tougher but brittle. It comes in many colors, but gets expensive in colors. Sometimes I get teflon-impregnates hard anodizing, very expensive and limited color choices but very tough. I've had my wheels powder coated, it's great for wheels and shouldn't peel, but it's not indestructible. Curbs and tire stores seem to do the most damage.
