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topic 10039

Does Chrome Plating of Alloy Wheels weaken them?


I have discovered that some auto manufacturers recommend "against" chrome plating aluminum alloy wheels. The claim is that it weakens the aluminum. I have included one such warning:

TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE: April 1991 REF. NO. MBNA 40/18
SUBJECT: ALL MODELS CHROME PLATING OF MB LIGHT ALLOY WHEELS

Chrome plating of MB light alloy wheels is NOT recommended. The reason that we do not recommend chrome plating is as follows: When chrome plating an MB light alloy wheel, the wheel must first be anodized (copper plated). The difference in EMF (Electro-Motive Force) values between copper and aluminum results in electrolytic corrosion with aluminum being the sacrificial metal. This will result in weakening of the base metal as well as poor adhesion of the subsequent plating, and thereby premature flaking of the chrome finish. Wheels of cast light alloy, with their porous surface, are even more susceptible to this condition than those of forged light alloys. Dave

Are there methods of plating, that are widely available and cost effective, that avoid the condition mentioned in the memo above? I would like to have my Mercedes E320 alloy wheels chrome plated. Can it be done without adverse effects?

Rene T [last name deleted for privacy by Editor]
- Dallas, Texas


 

Chrome plated wheels certainly can be trouble. And if the wheel is badly scratched on a curb, you could get this galvanic action. But the fact is, most chrome plated wheels are aluminum alloy.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


 

Dear Rene:

Although aluminum is not easy to plate, industry has found ways to properly prepare it, not all of which include copper or anodizing. Obviously porous aluminum castings represent almost impossible tasks for any plater, but I am surprised to know that MB uses them as wheels for their cars. As they themselves are not recommending it, you should follow their advise and not plate them. Instead, get a set of good looking chrome plated wheels of a recognized and guaranteed brand.

Regards,

Guillermo Marrufo
Monterrey, NL, Mexico



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