Why do alloy wheels get plated with copper before being nickel plated?

A. Hi Chadi. When you speak of alloy wheels, I'm assuming you mean pressure cast aluminum alloy. One reason for using copper is because it is easily buffable for mushing into pits or to increase the lustre of the wheel. Actually there are a number of competing technologies and the best one may be electroless nickel plating before the copper plating. Good luck.

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A. Mr. El Refaei, some of these issues may require plating books and plating journals, not just the web, because it's quite difficult to explain in a paragraph or two how bright nickel is cathodic to semi-bright nickel, and why it is thus beneficial to have at least two layers, and how a third pixie dust layer may improve corrosion resistance even more, and the fact that chrome plating always follows nickel plating in these cases anyway. And why copper is better for show chrome than additional nickel layers, and why electroless nickel can be beneficial to alloy wheels ... It takes many pages to explain, but our "Intro to Chrome Plating" should be a good start.

The multiple layers of nickel have nothing to do with shine. One layer will be as shiny as five. The multiple layers have to do with corrosion protection, the most essential point of which is that bright nickel is cathodic to semi-bright nickel such that corrosion can be made to spread laterally through the bright layer in preference to penetrating through the semi-bright layer and exposing the substrate.

But now I must wonder if you understand the need for preparation and zincating, and that the copper must be copper cyanide at the point in the sequence where you have placed it? We trying to help, not give you a hard time, but the subject is fairly complex. Please return after you read the Intro we suggested. Good luck!

A. The copper plating is done not only to give a good easily polished surface, but also to level out any imperfections in the alloy base. It is also there to help the corrosion resistance of the alloy base, and that is why it is used in preference to electroless nickel. Besides, electroless nickel can be highly stressed and may present adhesion problems to some alloys. I am not sure why there are three layers of nickel, but it could be (you don't give many details, so this is little more than a guess) that the first layer is electroless nickel as Ted suggests. However there will be two other layers if the plating is any good. These two layers are called "duplex nickels"; one has a columnar structure and the other lamellar. This also helps in the corrosion protection of the article being plated. Perhaps the third layer is on top of the duplex layers and is used to level the final coating prior to putting down highly reflective chromium.