johnH20
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| posted on 2/12/11 at 04:00 PM |
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Powder coating wheels- Q for metalurgists
This is a question for the metalurgists on here. Cast wheels ( if they are any good ) will be heat treated at some stage in their manufacture. I
don't know what the temperature is likely to be but obviously powder coating involves some degree of heat too. Is there a conflict here, that
is, will the powder coating process adversely affect the metal structure in some way? Any other issues ? TIA.
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Chippy
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| posted on 2/12/11 at 04:21 PM |
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From memory the wheels are heat treated to remove inbuilt stresses caused during casting, so would have thought that any heat during powder coating
would not cause any concern. IMHO Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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hootsno1
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| posted on 2/12/11 at 04:26 PM |
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Yes you can powder coat ally wheels i have done 3 set to date and have no problems after heating up to cure the powder 
If a little hammer won't fix it get a bigger hammer
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wombat
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| posted on 2/12/11 at 04:41 PM |
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What is the best prep before powdercoating?
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leon51274
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| posted on 2/12/11 at 04:53 PM |
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A good powder coater will shot blast, then bake the wheels prior to powder coating at a very high temp to remove any gases within the cast, then etch
prime and polyester powder coat 70-80 micron. You get special ovens that are about 10 times the size of a domestic oven but they go up to and prob
over 400deg, they can also be used to bake the paint off as powder coating can be a bitch to shot blast off.
My wheels had this full treatment and powder coated matt black, i then had them powder coated with a clear lacquer which gave a real deep gloss finish
and also made them really easy to clean. It did however show any slight scuffs so you have to be careful in making sure you clean with a very clean
sponge.
Cheers
Leon
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hootsno1
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| posted on 2/12/11 at 05:05 PM |
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Sand blasing, walnut shell is good as it dont pit the wheels as much, then a good wash down with meths as it will evaparate and remove any dust that
is left on the wheels, dont leave them once you have cleaned them as dust will settle on them and wear latex gloves as the oil in your skin will stop
the powder from sticking to the ally. 
If a little hammer won't fix it get a bigger hammer
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Litemoth
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| posted on 2/12/11 at 05:27 PM |
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I think heating can cause distortion if the alloy wasn't fully annealed originally.
Conversely:
If memory serves, I think aluminium alloys are rapidly age hardened (in the lab) by freezing them. This brings on embrittlement and makes them more
susceptible to cracking.
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loggyboy
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| posted on 2/12/11 at 05:33 PM |
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Powder coating needs about 180 degree, I would expect brakes to reach temps around that level (or more?).
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fullpint
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| posted on 2/12/11 at 06:33 PM |
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Heat treat invloves MUCH high temp than powder coating. They ramp up the temp over a period of time until the req'd temp is required. Its then
held at this temp for a certain time span before being ramped down slowly..
Powder coat cures between 180-200 degree's.
Best prep.. Details should be show on my web site mate. I would paint strip first prior to blasting.. Do not use steel shot tho.. A pre-heat is
required to de-gas the wheel.
I've over 28 years in dealing with magnesium wheels. Refurbishment and can powder coat most metal parts. Visit my web site if you wish..
www.tpcs-magnesium-refurbs.co.uk
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johnH20
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| posted on 2/12/11 at 06:59 PM |
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Thanks Fullpint, now I am getting some understanding. 400 deg ( as above ) for paint removal scared me! I have seen OEM refurbed wheels ( not any old
made in 'nowhereland' aftermarket ones ) fail on track days. The results are not pretty.
The fact that some people have had powder coating done successfuly does not really answer my question. I know that 'a little knowledge is a
dangerous thing' but in this case I think the reverse is true. Further contributions welcomed, I need the LCB knowledge!
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fullpint
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| posted on 2/12/11 at 07:09 PM |
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400 degrees may relate to the F scale which is about 204 degrees C...
I've over 28 years in dealing with magnesium wheels. Refurbishment and can powder coat most metal parts. Visit my web site if you wish..
www.tpcs-magnesium-refurbs.co.uk
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Litemoth
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| posted on 2/12/11 at 07:25 PM |
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I think the amount of heat cycling (including frost etc) they've seen during their lives and their age will contribute most to their remaining
strength and their likelyhood to fail in use....as well as the original chemical composition, correct annealing, porosity, cold shutting etc.....The
odd heating to 180 degrees wont contibute that much to the failure likelyhood risk.....
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johnH20
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| posted on 5/12/11 at 06:05 PM |
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Thanks Fullpint, I have saved your website for future use.
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