thought i post here to see if anybody here knew of or have experiece w/ powder coating. thank you
http://my350z.com/forum/showthread.php?t=326950

-vincent
Omega Werks
ClearBra/Tinting

 

Axis wheels are sand cast and generally not the best wheels. Powder coating them most likely made them even weaker due to the high heat needed to get the coating to stick. This sucks but I'm almost positive Axis won't replace them because they were powder coated and thus voided any type of warranty..

 

its not the powdercoating, but the agressive sandblasting they do to get the old paint off. Sandblasting adds surface hardness to metal, if you already have a fragile wheel like that taking away any amout of 'toughness' away could cause a crack, saw the same thing on a set of corvette wheels a while back. People blame the heat but PCing only bakes at 350-400 degrees, AL needs to be heated to over 1100 degrees before it will show any molecular change.

<==== two semesters of metalurgy

 

axis on a 350z yah seems bout right

 

problem solved!

 

My cousin had 3 of 4 original 95 Ford Cobra R wheels crack at sears after having them powdercoated. The car was a 93 mustang with everything from the griggsracing catalog on it and a set of Khumos. The wheels were freshly powdercoated the week before the event and only had maybe a season of use on them. After speaking with Bruce Griggs about it after the cracks were discovered, (my cousin needed a set of wheels to drive home on and Griggs had a set at the shop,) he said that it most definitely was the powder coating that weakened them. According to him, even 350-400 degrees will structurally damage a wheel if the cooling isn't properly controlled and the oven heat is not consistent. Most people probably won't have an issue on the street but, throw on a set of sticky tires and take it to the track and suddenly, wheels start breaking.

I too saw the pics of vette wheels on another forum. I've also seen a few other sets of wheels that have broken at the track as well. All had been to an aftermarket powdercoater. After seeing two sets break, I will never have any of my wheels powdercoated if I plan on taking them to the track. It's just not worth it.

I agree that sand blasting causes surface hardening but, the wheels my cousin had coated were stripped by another media. I think it was walnut shells but, I'm not sure. It might have been plastic beads. Walnut shells are more gentle than sand and don't cause nearly the heat buildup. It was about 10 years ago that this happened so my memory isn't that great.

Also, I know of a few shops that just won't powdercoat wheels anymore because risk.

Just my $0.02 of second hand knowledge.

Bill

 

Couldn't find the original article I had on this subject but a quick Google search brought up this thread which confirmed my original thought that Al starts to age at 350 degrees.

http://www.eng-tips.com/viewthread.c...151053&page=10

Most common Al alloys start to age between 325 -400 degrees. Now based on this discussion, an hour of this temperature will cause some artificial aging of the metal but, it won't be significant.

 

wow, very interesting info, I never studied anything about AL losing any strength at temps so low,

 

+1 for Rota. My old yellow power coated wheels were sand blasted, re-powder coated and are still holind up strong!

 

Time for new wheels? Talk to Subydude for some staggered offset lovin'. LOL.

 

thanks guys...ill pass on the info to him. he is now looking into Work Kai monoblock for his Z. lets hope it comes in black so he doesnt have to PC it

 

From experience. 180 degrees C will increase the hardness of aluminum by 10-20 BHDN points, depending on the time of exposure. So, in theory, powder coating wheels outside the plant can actually make them brittle depending on how long and what temp the wheels were exposed in the oven.

 

Finally some numbers on this topic. I new there was some science behind this. Thanks for dropping knowledge Krinkov.

 

Did you really "repair" that wheel??? OMG! Danger to manifold!

 

well now this has got me looking at the heat curing too and the fatigue temp of differnt AL alloys.
looking for my non-ferrous metallurgy book from 5 years ago