Paint or powder coat wheels

campbellju

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Staff member
Not a very exciting thread! I know I'll get straight answers here.

I need to get the 19" wheels on my other car fixed as they bend and crack at the hint of a pot hole. I was just going to get them sprayed as I wasn't that fussed but powder coating is not much more. I've had wheels powder coated in the past and they've been fine. More hard wearing but not impervious to damage.

What do people prefer nowadays and how easy is is it to strip back the powder coat in a few years time when they'll need doing again?

Jim
 

Fast Guy

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Staff member
I've seen a couple of thread over the last year about wheels failing after power coating. Presumably due to the heat process involved.
 

johnny gtir

Well-Known Member
Two things on powdercoat be carefull what temp they bake them at as sometimes its too high and can risk altering the property of the alloy and making it brittle. To get it off in the future they will just blast them.
Some powder coaters do inside of wheel where it bolts to hub and can cause issues to ballancing them and carefull how thick they go for fitting spigot rings or center bore again when refitting. Unless others know different i struggled to find a filler etc that would not create air bubles when they bake powder coat

issues that can be avoided when painting for one csn be baked at a lot lower temprature
others will add or correct me but hope this helps start your thoughts
 

vpulsar

Well-Known Member
I think what matters most is how well the wheels are prepared before what ever coating to use, Not sure what I prefer I'd just want them looking perfect afterwards.



Rob
 

red reading

Active Member
Two things on powdercoat be carefull what temp they bake them at as sometimes its too high and can risk altering the property of the alloy and making it brittle. To get it off in the future they will just blast them.
Some powder coaters do inside of wheel where it bolts to hub and can cause issues to ballancing them and carefull how thick they go for fitting spigot rings or center bore again when refitting. Unless others know different i struggled to find a filler etc that would not create air bubles when they bake powder coat

issues that can be avoided when painting for one csn be baked at a lot lower temprature
others will add or correct me but hope this helps start your thoughts

Exactley as this man says,
 

keastygtir

Well-Known Member
Do you mean the bolt holes? I had my wheels powder coated and I always have trouble with wheel wobble. I thought it was tyres camber and everything else. I hadn't considered it might be the powder coat
 

red reading

Active Member
Bolt holes and the surface that sits against the disc face, if not cleaned off will cause you trouble...have your wheels got the right size centre bore for the gtir hub as that should centre the wheels correctly to stop you issues...if not have they got spigot rings
 

johnny gtir

Well-Known Member
Where the face mates up be carefull you do get it right as just sanding untill powder coat comes off might be uneven like any sanding needs to be flat or even to match mating surface.

as said the only or one way to get the wheel right is alloy weld and smooth off any or most other fillers create air when baked ie filler or spray filler ,bodge even the highest temp industrial metal filler bonder i could find on the net and off shelf when powdercoating but which can be used if painting to cover curb marks and make wheels look perfect and as rob says the key is in prep work or condition of wheel,

i knew about the baking due to previos advice off you danny listened and learnt from your advice so glad you agreed with the comment lol
on other than wheels i love the look and finish my local powder coaters gets they blast then use a rust treatment protector with long life then coat ontop stuff looks the nuts and stands the test of time not like the other coaters local look at the item the wrong way it chips off
 
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campbellju

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Staff member
Thanks gents. I'd heard heard of issues with powder coating too due to the heat treatment but when I said this to the wheel guy he didn't seem to think it was an issue. Good to know I hadn't imagined it. I think that was why last time I got these 19" wheels sprayed as I knew it was safer. The wheels I refurbed before that were on the R which were powdered but those alloys are proper compomotive rally wheels that laugh at pot holes. Problem is with paint as Johnny says, you look at them the wrong way and it chips off.

Does anyone have personal experience of a wheel failing after powder coating?

I'll do some more searching on these wheels to see if the metal alloys have a known issue.

I'm leaning back to painting again
 

red reading

Active Member
The heat issues also come from the blasting process jim, sometimes the p/c is a shit to get off (my mate owns a powder coating company), you can get them chemically stripped and then lightly blasted, alloy type and spoke thickness will be your factors on blasting, I am sure the worst issues heard of were Mitsubishi evo enkei wheels of one model snapping the spokes after coating and oz super legeras....was a while ago all off this
 

campbellju

Moderators
Staff member
blimey, that's more than a hairline crack!

Thanks for the pointers Danny, My google searches are more effective. The powder coating needs to be done at high temp. You might want to anneal the paint but you don't want to re-anneal the alloy. The penny has dropped. I work in the glass industry so understand the concept of annealing. The problem is that the process itself may not intrinsically damage the wheel but if you cool down the alloy too fast you can introduce new stresses and strains into the wheel. If you cool it too fast it's like quenching which will be bad for the alloy and can lead to failures.

So the high temp PC process I won't entertain for aluminium alloy.

There is also a low temp PC bonding process that uses electrostatic rather than high temps. I believe the temps are still 100 to 150 Deg C but this should be below the annealing point of the alloy. Anyone any experience of this?

The PC on the mounting surface and issues with sealing on the rim seem to be well documented and should be masked before the coating by a competent shop. Incompetent PC shops cause problems.
 

red reading

Active Member
I know my friend turns the oven off and allows to cool without opening the doors for some stuff, tbh I would not have wheels done that are delicate in design or by someone who is not very knowledgable...I used to have magnesium alloy wheels on my motorbike and they were a nightmare to look after so am very dubious of anything to do with heat and alloy.
 

campbellju

Moderators
Staff member
I'm no expert but your mate sounds like he is on the right lines.

Large glass pieces for major building projects take 12 hours to toughen at similar temps. The cooling cycle is actively controlled over 4 hours. We had a problem with our glass in a major railway station where a pane would just explode for no reason. The issue was the heat from the sun causing strains induced during the toughening process. The root cause wasn't the toughening process but minute impurities picked up in the glass that caused unwanted stresses during the annealing. Less than 5 in 1000 panes failed but the company had to replace them all for obvious reasons.

My analogy with wheels is only 5 wheels in 1000 might fail and those 5 might only have failed from doing trackdays where temperatures rise like the sun on the piece of glass. Many wheels might still have issues but not catastrophic. I don't want to take the chance.
 

johnny gtir

Well-Known Member
I personally seen a car at a mates garage and spotted a hairline crack on a spoke closer look all 5 spokes were cracked so checked them all and all 4 wheels were the same and some cracks worse they were a thick spoke similar desing to comp mo 5's told the owner who was shocked and replied the wheels were of no age bought new but off e bay so must of been cheap copies of poor quality alloy very dangerous couple spokes looked close to doing what the pictures in the link were and parting. Best of it is car was modded and often drove at speed
 

campbellju

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Staff member
Quick update. After further browsing, the main issue seems to be with forged alloys where the annealed strength is part of the design. If you weaken the forging process then you are directly weakening the design strength of the wheel. If there is surplus mechanical strength in the wheel then you can get away with it. If it's a lightweight wheel there is less metal and less tolerance for any weakening.

Whether the wheel cracks or not is down to the accuracy of the process by the powder coater, the strength of the wheel and a good dose of luck when you next hit a curb or pot hole.

My wheels are lightweight but are spun cast so in theory are less susceptible to weakening from heating up the alloy again. Even though the suggested powder coater seemed professional only heating at 180deg C for 20 minutes, I thought the additional risk even if low wasn't worth the effort.

The wheels are already weak enough which is why they needed to be fixed so they didn't need anything else to risk weakening them further.
 
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