On Mon, 30 Jul 2001, Fli GLi wrote: > I want to do the same thing to my G60 rims on my GLi. I did some research > and found out that powder coating is much better for rims than painting. > It's tougher and since rims are subject to quite a bit of road rash, that > would be a good thing. It would suck to have paint chips on your rims. > > I did some checking locally (Rochester, NY) and found a shop that would do > the powered coating for b/t $120-180, depending on if they had the color in > stock or had to special order it. The only other cost is the have them > sandblasted b/f powered coating, ~ $12 a rim. A powered coating shop might > sandblast too, the one I called didn't. >
Make sure that the place you take your wheels to have them powdercoated knows what they're doing. Using powders that cure at too high of a temperature can actually damage the crystalline structure of the aluminum in the wheel. I found this on a powdercoating info web site: A metallurgist friend told me a few years ago that things like aluminum wheel spindles should not be powder coated. He explained that aluminum billet material (6061-T6 ?) changed crystal structure at a critical temperature around 410 degrees F (as I recall). The thrust was that the heating step would adversely affect the strength of the material. Non-structural components would be OK, but not something that "holds the spokes on". The metallurgist is correct. Products like wheel billets, scuba tanks, etc. can be powder coated, but only with powders which cure below peak metal temperature of 300 degrees F. The magic temperature is about 275F. The crystalline realignment at 400 degrees F causes the previous ductile aluminum to become brittle. Imagine the catastrophe when an 80 cu. ft. scuba tank explodes under 3000 psi pressure after an unauthorized powder coat (this actually happened). To my knowledge, all Aluminum wheels and other strength-critical aluminum components are powder coated with these cooler curing powders. Heating Al alloys above this temperature causes a granular rearrangement of the metallurgical structure resulting in a significant change of bulk properties. The tensile strength of the metal is dramatically lowered, much like a stress relief anneal on a steel piece would do. The resultant metal is not as strong, nor will pressure vessels made of such treated aluminum (e.g., scuba tanks) hold near the pressure that they were originally rated for. Since wheels are essentially load-bearing structures, they should never be heated like this unless the alloy is known to tolerate it well. _____________ List Sponsor: http://www.netsville.com To remove yourself from this list, send mail to [email protected] with 'unsubscribe a2_16v' in the body of your message See us on the web at http://www.a2-16v.com Visit the 16V Homepage at http://www.gti16v.org
