Baking paint on alloy wheels - How hot to go?

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Hi, I'm getting a shipment of 13" alloy wheels for my Dodge Colt. I'd like to repaint them with Duplicolor rattle can wheel paint. How hot can I bake the paint without damaging the alloy wheel? they're aluminum alloy machined wheels. The last set of wheels I painted were steel, and I baked them in my kitchen oven at 325 F for half an hour. Will alloy lose its strength at that temperature?
 
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I've had powdercoating done many times on aluminum, including wheels but mostly on fencing and gates. The powdercoater I've used has their ovens typically set at 300-325*F unless a high temp powder is required (not for aluminum but for some industrial components). I would not go over 400*F with aluminum. I think your 325*F idea is safe.
 
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Just make sure they are in a warm place and they'll turn out as good as possible with spray paint. no need to get them over 90*f. 350*f will not hurt the allow in any way, annealing occurs around 800*f
 

Kestas

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It's not annealing that you have to worry about, but the overaging at elevated temperatures. It's the aging process after solution treatment that gives strength to most aluminum alloys. Overaging results in loss of hardness and strength. I would try to stay below 325°F and use the minimum amount of time necessary for baking. I'd worry about anything over 350°F. Alloy wheels are safety critical items on a car.
 
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 Originally Posted By: Kestas
Overaging results in loss of hardness
My wife is concerned about this!
 
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 Originally Posted By: Kestas
It's not annealing that you have to worry about, but the overaging at elevated temperatures. It's the aging process after solution treatment that gives strength to most aluminum alloys. Overaging results in loss of hardness and strength. I would try to stay below 325°F and use the minimum amount of time necessary for baking. I'd worry about anything over 350°F. Alloy wheels are safety critical items on a car.
Interesting. I didn't realize a temp as low as 350 would/could cause any kind of change so I've now read up a little on overaging. will it do it just with heat or does it need a solution also?
 

scoobie

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to be on the safe side, i'll bake a little longer at 280 F. thanks for the tip, that's exactly what I was looking for - over aging the metal and making it go brittle. The last thing I want is to ruin the alloy. I just did a bit of reading, it's interesting that the solubility of the metals is higher in solid hot alloy, and the quenching process locks this in.
 
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scoobie

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just looked a bit more, apparently 135C or 275F is still bad, maybe just keep it at 250 for 20 minutes. 1. Semifinished products of wrought heat resistant aluminum alloys D20-1, D16, and VAD23 undergo hardening and softening at 150°, 135°, and lower temperatures under the influence of tensile stresses; hardening is due to additional precipitation of hardening phase and evidently to phase strain hardening; softening is due to coalescence of the precipitated phase. 2. Less aged semifinished products tend to harden more under high stress equal to the long-term strength for 100 h; intensive hardening of semifinished products of alloys D20-1 and D16 occurs at 135°; hardening in semifinished products of alloys AK4-1 and VAD23 also beings at 135 and 150°. 3. With increasing temperature and decreasing stress the coalescence of particles predominates, the acceleration of which in semifinished products of alloys D20-1 and D16 leads to precipitation of the less heat resistant CuAl2 phase and a heterogeneous partially recrystallized structure in extruded semifinished products of alloy D16. 4. Extruded semifinished products with a large-grained recrystallized structure tend to harden more. The long-term strength of these semifinished products may be more consistent than that of products with a fine-grained equiaxed structure. In the direction along the height these products are hardened less and have a lower long-term strength than those with a fine-grained equiaxed structure. 5. The tendency of the alloy to harden and soften during long-term strength tests can be judged from the change in the long-term ductility — the larger the slope of the curve, the greater the hardening. An increase of the reduction in section during long-term strength tests characterizes intensive softening of the alloy during necking.
 
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