Clear-coat problems on '96 wheels

I have had my wheels refinished and the clear-coat blisters on the spokes of two of them. They have been redone several times, with many solvent cleanings, and the same occurs. I am looking for replacements. I need a front and a rear @ 16" and 17". If anyone knows what the cause is, and a solution, I would love to hear.

I have found that only a few places can clear coat polished or machined wheels and have it stick , you should look for those who will guarantee it.

factory clearcoat finishes are based on 'clear anodizing' acting as a primer. if you simply clear a polished part, it will eventually peel. always. if you are dead set on clearing the wheels then your best bet is to have them stripped, polished, clear anodized and then clearcoated for that last layer of protection.

swerve said:

factory clearcoat finishes are based on 'clear anodizing' acting as a primer. if you simply clear a polished part, it will eventually peel. always. if you are dead set on clearing the wheels then your best bet is to have them stripped, polished, clear anodized and then clearcoated for that last layer of protection.

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This is simply not true , anodizing CANNOT be successfully done to a cast part unless it is 500 series and higher (most cast wheels are 356) , it will come out porous and pock marked - BELIEVE me - I tried it on a few occasions (even after being told it would not work) - even low quality aluminum machined parts will not anodize properly.

The factory clearcoated wheels are machined (allowing the clear a rough surface to adhere to , even so I have found that only certain shops have mastered the process.

Also painting or clearing an anodized part (along with being pointless) will not work very well due to the paint not being able to adhere to the hard surface.

Read more here:

http://www.alphametal.com/TechnicalNotes.aspx#castings

i think you missed the point- the wheels are machined already so there is no porosity. clear anodize is the first layer which acts as a primer for the clearcoat and yes, it adheres just fine, much better than raw metal. if you try to anodize a raw casting then the results will be crappy, like you said.

Powder coat near chrome finish.

It has a ghost chrome, titanium, gun metal combined effect to it.

swerve said:

i think you missed the point- the wheels are machined already so there is no porosity. clear anodize is the first layer which acts as a primer for the clearcoat and yes, it adheres just fine, much better than raw metal. if you try to anodize a raw casting then the results will be crappy, like you said.

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If you were to anodize the cast wheel which has been machined - the anodizing process will expose the pores in the metal , you will end up with a machined wheel covered in pinholes that look "burned" into the surface , I have tried it - somwhere I have a picture , I'll try to find it.

angus said:

If you were to anodize the cast wheel which has been machined - the anodizing process will expose the pores in the metal , you will end up with a machined wheel covered in pinholes that look "burned" into the surface , I have tried it - somwhere I have a picture , I'll try to find it.

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The same for powder coating wheels or metals. The heat will cause flaws to form in the powder coat....

BATMANs said:

Powder coat near chrome finish.

It has a ghost chrome, titanium, gun metal combined effect to it.

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Yes , this finish is achieved by applying various coats of silver over a black basecoat , we were doing this on interior parts in the 90's and as the paints improved , the process could be made more durable.

Not sure how this relates to clearcoat sticking to a wheels though...

angus said:

Yes , this finish is achieved by applying various coats of silver over a black basecoat , we were doing this on interior parts in the 90's and as the paints improved , the process could be made more durable.

Not sure how this relates to clearcoat sticking to a wheels though...

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Are you talking about painting or powder coating?

I was suggesting a different route. I faced a similar situation on another car's wheels and opted for powder coating....

BATMANs said:

The same for powder coating wheels or metals. The heat will cause flaws to form in the powder coat....

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It is not for the same reasons though , anodizing actually converts the top layer of aluminum to oxide using a chemical solution and electricity , if you have a porous metal , the pores will be eaten away and thus the pitted surface will show through.

i am not going to argue with you, i have no idea how crappy of a casting you tried to anodize. all i know is i have performed this process on cast parts that were machined and there were no issues. think aerospace castings- most of them are machined and then anodized on daily basis.

edit: before someone points it out, i did specifically mean castings, not higher quality forgings.

swerve said:

i am not going to argue with you, i have no idea how crappy of a casting you tried to anodize. all i know is i have performed this process on cast parts that were machined and there were no issues. think aerospace castings- most of them are machined and then anodized on daily basis.

edit: before someone points it out, i did specifically mean castings, not higher quality forgings.

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I did say that the aluminum needs to be 500 series or higher , since aerospace castings probably are, this is why you can do it

- HOWEVER -

I did state that most cast automotive wheels are A-356 - YOU CANNOT ANODIZE THEM SUCCESSFULLY - I HAVE TRIED IT - both machined and polished and it was a waste of time and money , I did it after being told that it would not work and just wanted to see for myself.

I am not arguing with you , I just wanted to save others the trouble of finding out the hard way like I did.

If you read the link I posted it is clearly outlined:

"Cast aluminum parts in general will not anodize as well because of their tendency toward porosity. Pores do not anodize and contribute to the same type of problem that highly alloyed aluminum parts encounter. Good high-density castings without porosity will anodize with good results. It should be noted that in color anodized castings some difference in color will exist between machined surfaces and the natural as cast surfaces. Some of the better casting alloys are 514, 518, 520, 535, 713, and 771. Again the same principle applies: higher purity aluminum, (less alloys), anodize better, producing better finishes."