Electro-plating bismuth-aluminium-copper alloy

A. Hi, Siarhei

You are right that I might not understand the technology of what you want to build. Conversely, you may not understand the technology of plating well enough to achieve what you wish. I think you should go to a specialty plating shop and have them assist you with this project.

I would not say that it is impossible to do what you want to do, but the barriers are imposing even for a skilled electroplater with decades of experience. To try to accomplish this with no electroplating experience is not going to get you anywhere very fast. Some of the barriers are that, in general:
- you can't plate onto aluminum without a zincate pretreatment;
- you can't plate aluminum or any aluminum alloy out of an aqueous solution;
- you can't make up plating solutions for this mix by dissolving the metal in acid;
- you usually don't make plating solutions, you buy them so that you can take advantage of the decades of development effort that preceded your experiment;
- it is difficult to plate binary alloys and exceptionally difficult to plate ternary alloys because of their differing potentials (please review the Nernst equation). Consider visiting a prototyping plating shop and discussing your project with them. Best of luck!

A. Siarhei, plating a bismuth-aluminium-copper alloy onto an aluminium substrate is not an easy task. As Ted says, it is impossible to electrodeposit aluminium or aluminium alloys from an aqueous bath - it just doesn't work. However, there is an increased interest in electroplating from "ionic liquids", where the problems associated with aqueous technologies are not found. A couple of British Universities are looking at the technology, so do an internet search and find out more details about it. One of the possible advantages of this technology may be that depositing onto aluminium will not require the usual zincate treatment that Ted quite rightly refers to as being essential for aqueous deposition onto aluminium. Alloy deposition of this type of formulation will be very problematic because of the wide ranging positions of the metals in the electrochemical series, but with adequate complexing, it may be possible.

A. Hi, Rob.

It is difficult to plate onto magnesium, and it is difficult to plate bismuth. So the first question has to be: is an intermediate layer(s) permissible? For example, can we plate electroless nickel on the magnesium, then bismuth on the nickel?

Regards,

A. Hi Devan. I think it's more likely that your charm is, as labeled, sterling silver through & through than that it was deceitfully mislabeled.

The issue is perhaps that what you consider "polishing" is probably only tarnish removal, not actual metal polishing (which involves mechanically moving the metal). I'll bet any jeweler can shine it back up for you ... and if you learn a bit and do some practicing on scrap, you can probably do it yourself.

If you really want it gold color, the most practical thing, and by far the easiest is to have it gold plated. Very little gold is actually involved so the cost should not be outrageous. You could even try one of those "Medallion Liquid Gold" do it yourself kits. But the thing is, if it's not shiny before gold plating it's unlikely to be shiny after gold plating ... so polishing it probably needs to be done anyway. Good luck.

Regards,