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Plating chrome onto a gold layer

March 24, 2009

Dear industry experts,

I have a layer of gold that has been vacuum coated onto a very reflective nickel substrate. Can anyone inform me if it is possible to subsequently electroplate a thin layer of chrome 1-2 microns in thickness onto this gold layer so that it will adhere to the surface? My concern here is that the plated chrome layer will just peel off the gold layer. I do not have sufficient knowledge to understand why some metals to plate together with a strong adhesion and others just tend to peel away. The adhesion of this gold to the substrate is already excellent and meets my requirements. The chrome needs to be deposited through electroplating and not other coating methods due to the specific requirements of this product.

Any input here would be most appreciated. Please note that I will not be conducting the process in-house but outsourcing the process to another vendor so I am unable to elaborate more on the chrome plating process steps.

Thanks in advance!

Ronald Walliams
product designer - Reading, UK

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April 2, 2009

Hi Ronald,

I guess that I'm typical of other regulars of this forum that while I have been involved in electroplating for many years, I have never previously met the plating of chromium on gold. Nor have I had experience in vacuum gold deposition. That said, here ar a few thoughts.

I would have expected chromium to plate with good adhesion on the gold substrate, but would be concerned about the chromium causing the gold to detach from nickel. The adhesion of the very thin gold layer may appear to be good (and perhaps it is) because it is difficult to detach very thin coatings. A good test for adhesion would be to apply a thick coating of some back up metal and and then do a pealing test - just what you are proposing to do whether you intend it or not!

One micron of chromium is about the top limit for decorative plating. "Hard chromium" for wear resistance can be much thicker but becomes increasingly dull. I would expect 2 microns to give a degree of hazing. Does this matter in your application?

I can't be alone in wondering about the purpose of your application is!

Harry Parkes
- Birmingham, UK