Powder Coating for Alloy Wheels: Enhance the Look and Durability

• What is an alloy wheel powder coating?
• Benefits of Alloy Wheel Powder Coating
• The Powder Coating Process
• 1 Making a Support Jig
• 2 Wheel Preparation
• 3 Masking
• 4 Primer Application
• 5 Powder Coating
• 6 Curing
• Comparison to Electrical Powder Coating Systems
• Gassing Out and Casting Issues
• Popular Colours and Finishes
• Maintenance and Care
• Cost Considerations

The following stages in this blog item will be covered

• Making a support jig
• Wheel preparation
• Masking
• Primer application
• Powder coating
• Curing
• Comparison to electrical powder coating systems
• Gassing out and cast part issues
• The finished wheels

Making a support Jig
In order to easily handle the wheel from the powder coating area, into the oven and out again, it makes the whole process much easier if the wheel can be mounted to a skeleton frame.

To this end, we made up a box section frame that facilitated mounting the wheel through one of the wheel bolt holes and provided an easy-to-carry handle for the movement of the wheel.

 The other feature we built into this Jig was guide bars to the left and right of the Jig (the two legs on either side of the frame). The left to right dimension was slightly larger than the wheel diameter and smaller than the oven width. This provided protection against the side walls of the oven accidentally rubbing the powder off the wheel when putting in / taking out the wheel from the oven.

We have written an article on how to build your DIY POWDER COATING OVEN FOR £100.


Wheel preparation
Initially, all corrosion and flaking paint needs removing and the step between metal to existing paint smoothing out such that no step between these surfaces can be noticed.

The existing paint then must be lightly flatted out with 250 grit paper, so any blebs or imperfections can be removed. This process of flatting will also act as a key and help the new powder adhere to the existing paint.

 Attention also needs to be given to the wheel's mounting face that connects to the disc or hub. In our example, we used a dual-action sander to remove corrosion and clean this surface.

As part of the preparation stage, the valve also needs to be removed.

In our example, we cut the back of the valve off as we are fitting new valves to the wheel when the tyre is re-fitted. Also, any balancing weights and their adhesive need to be removed.

Masking
It's important to ensure any of the mounting faces are masked off, as the powder coating overspray may be challenging to remove afterwards. The areas we masked were the wheel mounting face and the conical wheel mounting holes.

 We used our high-temperature masking tape on the wheel mounting face and some old bolts to mask the bolt holes (conical area only); to hold the bolts in place we slipped an o-ring over the threaded section of the bolt to hold it in place.

Primer
Aluminium corrodes rapidly following the surface coating being abraded; thus it's essential to apply the etch primer as soon as possible to the bare surface to minimise this corrosion. We used a standard aerosol can of etch primer.

 The key with the etch primer is only to apply a thin coat and also allow it to dry thoroughly as if a too thicker coat is applied, it can craze and affect the final powder coat finish. If the crazing does appear, then simply rub it back with some abrasive paper and re-apply the etch primer. The etch primer can be applied to the whole wheel surface, but is only required on the exposed aluminium areas with a slight overlap to the original paint finish.

Powder Coating
First, make sure you can make contact (with a finger or attach the earth lead) with the wheel via what it's mounted to. We sanded an area on the Jig to touch while spraying.

You need to do this with our system to ensure the neutralisation of the static. Note we sanded an area at the front and rear of the Jig to make it easy when spraying the front and back of the wheel.

Next, set your gun up; this is best done by opening the regulator on the handle of your gun, closing off the regulator on your compressor, then holding the trigger of your gun in and gradually opening your compressor regulator to get a flow of powder out of the gun approximately 10" to 12".

The gun is now set. Before starting the powder coating of the wheel give it a good blow down with an airline to remove any debris that has settled on the wheel.

Now to start coating the wheel. 

The most important thing while powder coating is to cover the most intricate areas first, then coat the larger, more accessible areas last. This is because if you go over the large accessible areas first, it's easy to miss or put on a thinner coat in the intricate areas, as it's easy to forget where you have coated and missed a bit.

We started with the rear of the wheel and coated all of the inside and rear edges; we then coated the diameter of the rim from either side (this is the unseen area hidden by the tyre); this section needs a good clean coat of powder approx. 1" in from the rim edge, as this is the area that the tyre seals on. We then completed the face last but again focused on all the intricate areas first, then the bigger flat areas last. When the wheel was fully coated, we inspected it to ensure all areas were covered fully and we hadn't accidentally knocked any powder off.

Finally, because powder rests on large horizontal surfaces with no means of falling away with gravity, there is a risk that an excess of powder can rest in the lower section of the inside wheel rim. We overcame this by tipping the wheel back just over 45 deg in the Jig and allowing the excess powder will run out, thus leaving an even coating of powder in this area.

Curing
We carefully transferred the wheel to the oven and checked again that we hadn't accidentally knocked any powder off, as, at this point, it's easy to fix (much harder once cured). We set the oven to 180 deg c with the wheel in and watched the temperature of the wheel rise to this temperature.

 Make sure the wheel raises to 180 deg before starting the timer for 10 min's; as usual, when the air temperature of the oven is 180 deg c, the part depending on its thickness, may take several more minutes to raise to this temperature Note if you wait for the air temperature to hit 180 deg c and the cure for 10 minutes the wheel will most likely be under cured, wait for the PART to reach 180 deg c.

After the part has cured for 10 minutes at 180 deg c, let it cool down naturally; for wheels like these (20"), it took about 20 minutes before they could be handled. With the wheel still in the Jig, check it all over and if you are happy with the finish, unmount it and proceed to the next wheel. TIP if there is an imperfection for some reason, rub it out to a smooth finish and over coat the whole wheel again by repeating the coating process.

Comparison to electrical powder coating systems
Our Easy coat system, due to how we have designed it, is very good at overcoating parts multiple times, whether overcoating wet paint or powder finishes. This makes it ideal for the method used in this article. For example, we powder-coated one of these wheels with our professional box feed guns (retail price £4k+). We cured the wheel and the results were not brilliant! 

The issue with electrical systems being of a Corona charge design they do not perform well over coating parts and tend to exhibit inclusions in some areas when cured. We fixed this issue with our Easy Coat gun very easily by rubbing out the imperfections and re-coating the wheel.

Gassing out and casting issues
Sometimes with castings (many alloy wheels are cast), you can get gassing out issues. This is where either impurity in the casting or pockets of air can blow through the powder coat finish during the heating process. There are many ways of working around this issue, but we find the simplest way is to pre-heat the part to around 150 deg c to 180 deg c and powder coat alloy wheels while hot.

There is a little more skill involved in powder coating this way as you could apply too much powder due to the excess powder not being able to fall away; however if you spray the part evenly and apply a similar amount of powder as if the part was cold you should not have a problem. When the part is fully coated this way, re-introduce it to the oven, raise the part to 180 deg c and hold it there for 10 minutes, then let it cool.

We tested a small area on the wheels we powder coated for this article first to see if there would be a gassing out issue. We did this by prepping a small area, applying powder and curing it.

On these wheels, there was no gassing out issues present, thus we blended out this sample area and continued to complete the whole wheel.