I was doing a batch of wheels yesterday, so I decided to take photos and videos of the process so that you can get some ideas for DIY or even just be aware of what happens to your wheels when you put them in for a refurb
I'm just waiting on the last video to upload to photobucket and then I'll bombard you with stuff!
I've tried various chemicals to get the old paint off alloys, but this is the best stuff I have found to date.
It's a mixture of various things, but it is mainly dichloromethane and formic acid. I pour it into a large barrel and put water in on top of it. Because it is so heavy, the water floats on the top and the chemicals sit at the bottom of the barrel. Doing it this way has a few advantages. 1. The chemicals can't evaporate 2. You can't smell the chemicals 3. The chemicals get washed off the wheel as you draw it slowly up through the water
Looks lovely doesn't it
Here's a picture of some wheels before they go in the chemicals
And here's some after shots. This wheel has been dipped in the chemicals, but hasn't been rinsed with the hose yet
The same wheel after it has been washed
A batch of wheels that have been dipped and washed and waiting for shot blasting
i was gonna say, WOW that stuff changes the design of the wheels.
That it some cools stuff, Do you do this sort of thing a lot?
Once the wheels have been stripped back to bare metal using the chemicals, we need to blast clean them to get a mechanical key for the powder coat to stick properly.
There are two ways we can do this, depending on the finish the customer is after.
We can do it in here, using fine steel shot at 70psi blast pressure (Grade 3 Aluminium oxide is better, but this works out much cheaper)
Or we can do it in here using fine glass beads at 40psi blast pressure (this is almost like a polishing blast medium)
Here are the wheels after they have been blasted. Because there is no paint on them, the blast time is significantly reduced. The average wheel will take 4 minutes to blast, even with the old chemicals I was using a wheel would take 15 - 25 minutes so you can see how much time is saved.
But this wheel is destined for greater things, so it has been done in the bead blasting cabinet, you can see the difference in finish.
Last edited by George; 02-05-2009 at 12:20.
very cool
The preperation of the wheels takes longer than the blasting. It will take between 10 and 15 minutes to thoroughly prep a non damaged wheel, where a kerbed wheel will take up to 20 minutes.
This wheel required very little prep and just needed some masking up and a light going over with P360 sandpaper.
The next wheel has some light kerb damage, so we're going to need one of these
And perhaps some of this
Or this
Here's a close up of the light damage
Apply some quik steel
And use the DA sander to take it back down to the level
Here's a prepped wheel that has had shot blasting
And here's a wheel where the damage could be grinded out using the flap disc, it will then be sanded with the DA to get rid of the grinding marks
And here's what corrosion looks like after you've sanded a wheel, but this is so slight that the paint will cover it. If it was going a flat silver I would either grind this out or fill it with the isopon metalik, but as it's going metallic gold, you won't see it.
Last edited by George; 03-05-2009 at 08:31.
Now that all the wheels are prepped, they are ready to go in the oven, but we need to hang them up first. These are special wheel hooks and are copper coated so that they conduct the static electricity better.
And here they are all hanging up and ready to get blown down and put in the oven.
Because alloy wheels are porous (less so with forged wheels rather than cast), they have to be pre-baked at a temperature above the cure temperature of the coating so that they don't outgas. Think of trying to paint and then bake a sponge.
So we fill up the oven (This is the oven shrunk to 1/3 of full size for doing wheels.
And then we set the temerature we want to pre-bake the wheels at to get the air and moisture out of them.
And we set the pre-bake countdown timer
15 minutes is plenty in this oven as it has a very high airflow (20 air changes a minute) so it's very windy in there. A non fan oven would take about 40 minutes to achieve the same result.
Now we can sit down for a quick cup of tea before we start painting
Now it's time to set up the powder gun and get ready to powder coat the wheels.
This is where the magic happensThe booth has a waterfall and scrubber nozzles that filter the powder out of the air.
A selection of powder coatings
The rail that you see in the first picture is where you hang the wheels for coating, so this is earthed off so that the static has somewhare to dissipate to.
The gun is set up for the voltage that we want to put into the powder. 55kV is plenty for doing wheels as the powder will be melting straight on with the heat anyway.
This gun has a system that modulates the charge dependng on the distance from the route to earth, so that it doesn't overcharge the workpiece when you're trying to get into awkward corners.
Here are a couple of short videos of me powder coating some wheels. The first one is just a basic sparkley silver, the second is a metallic gold. If you follow the same order as me in the painting you will avoid overspray on the front face of the wheel.
For coatings with a very high metallic content we need to use wet paints, so we just use the powder coat as a base coat and lacquer, with a high metallic wet paint between the two.
So we'll need this little lot
The spray gun, filter, and paint are self explanitory, but we also need the infra red thermometer to check that our wheel is at optimum temperature for application of the coating.
Here's the wheel with the powder coat and wet paint colour on. This will be baked at 180C for 10 minutes to cure the wet paint before the powder lacquer goes on. For a shadow chrome effect the same wet paint is used over the top of a gloss black
And some of the powder coated wheels waiting for lacquer
Last edited by George; 03-05-2009 at 09:29.
very interesting and nice write up. always wondered how how powdercoating was done
The lacquer can go on cold, as the wheel has been sealed by the previous coating and won't outgas anymore.
It makes the wheel look like it's been covered with flour.
They all get loaded back into the oven now for their final bake to cure the coating.
And we set our oven to the cure temperature
15 minutes again is enough to cure the wheels in this oven, so it's time for another cup of tea
There we have it, the end result
And we just hang them up on the line now to let them cool slowly
Hope someone finds this useful
Very cool thread, always wondered how it was done!
Very nice.
Does the powder coat always come out at the same thickness all over the piece or does it vary slightly?
Is the wet painting between coatings to allow a specific colour to be applied? ie. I have my wheels paint WKO pearl white but seeing as PCing is a lot more hard wearing is it still possible for them to be done pearl?
How much do you charge for a set of 4 wheels?
Very interesting.Thanks for sharing.
This is an awesome thread, I've got some wheels I want to get painted and was thinking of getting them powder coated.
Shame your too far away otherwise I'd get you to do mine.
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