Clearcoat bubbles on wheels, what causes this?

[hemi1300]

Sorry, no pics, but almost every vehicle I have ever owned with clear coated wheels, the finish eventually starts to look like it bubbles up around the center cap of the wheel. Curious what would be the main cause of this? Have had my 14 ram laramie for a few weeks now and it has the premium chrome wheels (plastic chrome wheel cover to be exact), and want to avoid this happening on this truck if I can do so. Hoping, since my wheels are the plastic chrome cover, I won't see this bubbling on them a few years down the road

[marquez93]

Not sure if this is the same as what you are talking about, but this is what often happens to wheels that are machined finish with no paint and just a clearcoat on them. If you have some curb rash or even just a small chip in the clear, moisture can get under it and start to corrode the bare aluminum. If you don't do anything about it, it keeps spreading. This should not happen to chrome wheels. The main problem with chrome is if you don't take care of them, the chrome can start to peel off.

[Bryce]

[Sizzle Chest]

IMO: the brake dust when left to dwell can be caustic and cause the paint/clear to fail.  I have some Mercedes wheels that have the same issue.  I picked it up used and the damage was already done.  MB has some serious brake dusting issues that in my opinion contributed to this issue.

 

If you regularly clean and protect your wheels I do not see this becoming an issue.

 

 

Hope this helps! 

[1911A1]

This has happened to every factory alum. wheel I've ever had.Any damage to the coating that lets oxygen and moisture contact the aluminum starts oxidation that eventually pops the clear off the surface.Pretty typical in the northeast. 

[vobro]

Had a '12 Ram and Charger RT both with the chrome clad wheels. All 8 wheels started peeling from the barrel side, I suspect I sped up the process by washing the barrels often and bumping the edge with the handle from the Wheel Woolies. If they do start peeling be careful as the plastic can be very sharp

Edited September 10, 2016 by vobro

[LT1xL82]

This has happened to every factory alum. wheel I've ever had.Any damage to the coating that lets oxygen and moisture contact the aluminum starts oxidation that eventually pops the clear off the surface.Pretty typical in the northeast. 

Pretty much my experience in northern New York state. 

[hemi1300]

Pretty much my experience in northern New York state.

Exactly what i'm talking about. Is there any way to prevent this?

[Beemer]

Move?

 

 

Sorry. Couldn't help myself.

[Odds and Ends]

I see quite a bit of that on cars that roll through my shop. All of the chemical that gets laid down to melt snow and ice doesn't help either. Anywhere there is winter weather, you find bubbling clear, peeling chrome plating, and yes, as mentioned, it's very sharp, and other road related blemishes.

 

Although it probably won't look very good, in some cases you might be able to "seal" the incident where the clear is compromised by using some liquid clear coat. Not always, but it may help to keep it from spreading.

[LT1xL82]

Exactly what i'm talking about. Is there any way to prevent this?

Prevent? Maybe not, but I have seen some wheels fair much better than mine. My next new daily driver with these wheels will receive more cleaning and sealing than I have done in the past.

[CadillaChick]

This Bulletin from GM will explain some of it and the symptoms

 

http://www.revbase.com/BBBMotor/TSb/DownloadPdf?id=168614

[b_pappy]

Thanks for the link to the bulletin.

My personal wheels are also starting to show clearcoat failure. They have never seen snow, or salt spray, and they are carefully maintained. My belief is that the clearcoat can only take so many years of abuse, heat cycling and everything wheels are subjected to in use. Getting paint to adhere to a polished surface has never been easy. It is aggravating, not really sure of a better solution. Polished wheels require lots more maintenance, polished & clearcoated have "limited" life time, and chrome is an entire different look, that usually is more durable.

Back when I designed OEM wheels for FORD & GM (at Superior Industires) we subjected the wheels to durabilty testing that included salt spray and other environmental issues, along with rotary and radial fatigue testing. I don't remember the cycle time details though. Regardless, real life use the coating seems prone to failure eventually.

I'm looking for new wheels for truck now.

Best of luck with your situation.

[PHOKUS]

Thanks for the link to the bulletin.

My personal wheels are also starting to show clearcoat failure. They have never seen snow, or salt spray, and they are carefully maintained. My belief is that the clearcoat can only take so many years of abuse, heat cycling and everything wheels are subjected to in use. Getting paint to adhere to a polished surface has never been easy. It is aggravating, not really sure of a better solution. Polished wheels require lots more maintenance, polished & clearcoated have "limited" life time, and chrome is an entire different look, that usually is more durable.

Back when I designed OEM wheels for FORD & GM (at Superior Industires) we subjected the wheels to durabilty testing that included salt spray and other environmental issues, along with rotary and radial fatigue testing. I don't remember the cycle time details though. Regardless, real life use the coating seems prone to failure eventually.

I'm looking for new wheels for truck now.

Best of luck with your situation.

Bingo!

 

Most wheels will see clearcoat failure nearest the hub first as that is where the heat transfer from hot brakes takes place. X number of heat cycles later, the clearcoat begins to fail, exposing the bare aluminium beneath. As mentioned in posts above, once the Au oxidation process begins, there is almost no easy way to stop it. The further away from the hub it gets, the slower the oxidation process becomes due to a lower max thermal delta (difference) that portion of clearcoat has had to endure - thus is in better condition.

 

Salt and other chemicals further compound this problem and accelerates the damage being done by the thermal cycles.

 

The only true solution is to have the wheels pulled, tires removed, the clear completely stripped, acid-bathed to remove oxidation / contaminants, and re-cleared.

[Timmmay]

First off, hello all - new here but have lurked for some time trying to learn how to best take care of my vehicle. Thought I would share some of my experience/knowledge in an area that I'm quite experienced.  Please do not take my comments as challenges to what others have shared - that's not the intent, as there are all kinds of things that can cause wheels to look bad and not all are the same thing.

 

Like b_pappy, I was also a wheel designer for an OEM supplier (different company) and prior to that I worked in that company's test lab.  Like he says, the coatings are tested but it's only for like 1000 or 2000 hours with the tests that simulate corrosion. There are other outdoor tests that take much longer, but that is more for testing the UV damage and fading of color and/or clear.

 

True bubbles in or on clearcoat will be colorless or appear slightly darker - it's just a defect of the coating process that wasn't caught by visual inspection. Normally, these defects are attempted to be found by the manufacturer by way of visual inspection, segregation and then if deemed repairable, finessed out of the clear by light wet sanding and/or buffing (similar to body paint correction but in a smaller area).

 

I'm sure one of the issues others have brought up is filiform corrosion, which grows on the aluminum and under the clear. It will often be gray-ish green or yellow and look like a moldy or bubbling patch or even like it's "worming" on the aluminum surface.  It can appear under painted areas, but it's most commonly found on areas that are only cleared over bare aluminum (machined or polished).  If you're familiar with Airstream trailers/campers, they are notorious for having filiform issues as well.

 

A Google image search for "filiform corrosion on aluminum" will give plenty of examples on both wheels and the Airstreams.  If you happen to see the X scribe, that's how the wheels are tested - they're scribed down through the clear layer and into the aluminum, exposed to a corrosive and then heat & humidity.  Techs note the growth rates and the customers will pass or fail the test pieces.

 

Areas where filiform most often starts or appears will vary but it most often appears first where the clearcoat has lost its seal or areas where there was thin coating coverage.  The causes of this corrosion can be attributed to the breaks in the clearcoat combined with corrosives and/or humidity. The clearcoat breaks can occur starting with the manufacturing of the wheel (burrs, sharp edges, metallic components that are assembled together and rub like screws or bolts) or the breaks can happen through normal wear and tear (rocks or debris forcefully contacting wheels, clumsy techs dropping tools, tire installation/removal machines, pry off center caps or traditional clip-on wheel weights).  As most have already figured out, the corrosives are what we throw on the roads or are already in our environment and then the moisture and corrosives are exposed to heat and humidity which tends to grow this type of corrosion between clearcoat and aluminum.  Where you are located in the US does impact the length of time it takes for this type of corrosion to appear, but more often than not, it will eventually appear no matter where you live.

 

Once it starts, it's not going to stop. There aren't any proven methods out there for filiform correction, as filiform can pit the aluminum and damage it. About the only way to correct it is to have the wheels remachined and recoated - but even then, it's going to return at some point through normal use.  It might be slowed by way of washing, waxing, babying but that I am aware, there hasn't been any sure fire prevention or cure for this type of corrosion yet.

 

Anyway, I hope this sheds some light on a couple of wheel related issues for a few people.

Edited November 19, 2016 by Timmmay