I agree with swinglo.....being a co-owner/investor of a PC business it's standard procedure for just blasting then coating. There is no reason for a chemical dip if the proper blasting media is used. There are several choices of blasting media. It all depends on the metal underneath. For your wheels I would suggest using nut shells........ It sounds like a business creating more profit for themselves by taking advantage of a under-informed customer? I suggest shopping around.
A wise man once said "All you need is what's around you" Well, when I looked around I saw a pimp with a shiny pair of shoes and a 49 Mercury!