sea2skydad said:
"but painting raw aluminum has its own problems and I had serious doubts that I could do a satsfactory job myself."
What problems, specifically, John? I'm going to be replacing my rubber soon and I was planning on clear coating the wheels myself, after getting them blasted with walnut. Thanks, Greg.
You can certainly try to paint your wheels, and good luck. Raw aluminum starts to oxidize immediately after exposure to the atmosphere. The oxide surface coating prevents conventional automotive primers or paints from sticking very well, and you MAY end up with a paint job that will peel off in sheets when hit with a pressure washer.
To paint aluminum "properly" you must clean the surface with something like AlumiPrep, an acid wash, then _immediately_ follow up with an Alodine coating and a zinc oxide, or better yet, a zinc chromate primer coat. The latter is restricted and harder to get due to its rather toxic nature. If you are clearcoating, you would paint the clear right over the Alodine. The problem with clear coat is that you obviously can't use any sort of colored primer beneath it, nor can you sand the aluminum to get some "teeth", so you are forced to bypass an important step. You can use a two part epoxy primer also - but that gets very expensive and impractical unless you have spray equipment.
A rough walnut- or bead-blasted finish will offer lots of tooth to the clear coat, so you may be fine, but I wouldn't recommend skipping the initial chemical treatments.
I have NO idea what the wheel manufacturers do when they paint or clear coat a wheel, but they know the tricks and do the job under very controlled conditions. I have seen new painted and clear coated alloy wheels lose their coatings big time, so even the manufacturers screw up. I had drop dead gorgeous $600 BBS RKII wheels on a Saab 9-5 Aero that were losing the clear coat in chunks after a year of handwashing only, so even the premium manufacturers make mistakes. This is a main reason cosmetic faults aren't covered under the warranty.
All this stuff is available at aircraft supply stores. I just didn't want the hassle or risks of screwing up the process and having to do it over again. If I had decided to paint my Classic IIs I would have used zinc chromate primer followed by aluminum wheel paint followed by clear coat. I wouldn't have attempted clear over shiney aluminum.... Here are a couple of links - there are a number of "aluminum painting FAQ"s out there somewhere - it's worth researching the process before diving into the job.
http://www.wicksaircraft.com/catalo...ml?PHPSESSID=53ebd9a548b4e910f29f26f245bd4f12
http://skygeek.com/coating.html
John