Its_Lobelt

Hey guys I have a set of 993 chrome wheels that I want to refinish in black paint with a red lip or something similar. Now my question is how do I take the chrome off the wheel and prep it so the paint sticks. Thanks for any info in advance.

Matt H

Acid etch? Call a wheel repair shop and ask them. The chrome is a plating, under it is another metal.
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Its_Lobelt

Damn so its not easy like old paint removal.

IceShark

You take it to a plater and they will reverse the original process. Cost shouldn't be too bad since they don't have to polish things up.

My only concern would be hydrogen embrittlement, especially on a rim, but there are methods to treat to eliminate the problem, well, sort of. I never did get a real straight answer on this. But I was just having a strut tower bar rechromed so it wasn't the end of the world if it ever fractured.

No, this is not a simple "paint stripper" removal situation.

Matt H

The other thing I would be concerned about it the pitting. You might also talk to a powder coater, they might be able to blast them and PC them as cheap as having a shop remove the chrome.
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Oddjob

It is a reverse electro-plating process to remove chrome plating. Any place that chrome plates should be able to remove it. The chrome is very hard compared to the aluminum wheel, so unfortunately, I dont think you would be able to sand/bead blast it off.

Im not sure how well chrome plates to aluminum, so it is likely that the wheel may be plated with nickel first, and then the chrome is plated to the nickel. Therefore it would possibly be a two step process to remove.

I havent heard of hydrogen embrittlement associated with electro-plating, especially in a reverse operation. The hydrogen embrittlement that I am familiar with is a concern within the heat affected zone when welding.

You will need to have the wheels refinished after the chrome is removed. If there is pitting (usually shows up on the inside of the wheel first) you can have that polished off to a matte finish prior to painting or powder coating.

In the end, it will take a few bucks to remove the chrome and refinish the wheels; so it will be cheaper to just sell the wheels and buy a set with the finish that you want.

Matt H

oddjob, you are right about the two part. The aluminum is nickel dipped then chromed.
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KuHL 951

The major concern when reversing the electroplating (cathodic) process is selective pitting at "holidays" or flaws in the chrome. Current densities at the flaws will be much, much, higher than the surrounding hard chromium layer resulting in severe pitting and wormholeing of the aluminum. Anodic cleaning (anodic) is generally used on organically coated surfaces that display some uniform porosity characteristics. If "hydrogen embrittlement" (cathodic) wasn't induced during the original plating, it certainly wouldn't occur under the reverse process. A forged alloy under this reversed polarity could certainly experience "stress corrosion cracking" (anodic) given the right conditions. They are both forms of environmental cracking and display sudden failure. Either way you lose.

In short, I would highly recommend you sell the wheels and look for another set to refinish or polish just to be safe.

Its_Lobelt

Damn guys thaks for the info. I wanted to paint the wheels black to match the car but if it is a headache then I might as well sell em or trade em.

alpenweissisnice

Perhaps I'm wrong - definitely no authority - by understanding of the powder coat process is that is it "baked on"...As someone else suggest, perhaps a powdercoater could rough them up then powdercoat over the chrome...One the other hand, someone is always looking for blingy wheels for their "Rally Edition"...

SeaCay

Chrome plating does have the drawback of hydrogen embrittlement. Caroll Smith recommends low luster nickle plating for anything on a race car due to chrome's embrittlement properties.

The welding operating results in localized hardening of certain alloys, hardening isn't something that is desireable on items such as roll cages, and suspension bits.

Oddjob

After a quick check, the one thing missed is that hydrogen embrittlement occurs with steels. The harder the alloy, the more prone it is.

Looks like the main culprits/processes that introduce hydrogen into the steel grain structure are electro-plating (any type, not just chrome), acid cleaning (anodic or pickling), and welding.

I cant find anywhere where aluminum is susceptible to this type of embrittlement.