Practical Technology:

Nickel Free Plating: Making it Work

Part 2

by Dan Schafer

Electroplating with nickel was fun, because we could watch a transformation from an ordinary-looking copper surface to a bright silvery appearance. Then a quick layer of gold made the piece look like an expensive item from a jeweller's window.

In plating with nickel, the most difficult thing was to get the backs of our jewellery pieces bright. That was for two reasons. One has to do with how we make the jewellery and the second has to do with the nature of electroplating. Our enamel jewellery mostly has enamel on the front separated by little copper wires which outline the design. Therefore, the front has much less surface area to conduct electricity and be plated than the back.

The nature of plating is that the plating bath or solution is full of little ions of the metal to be electrically deposited. These flow to where there is an opposite electrical charge. Since the concentration of these ions is more or less even throughout the bath, there are more of them available per conducting surface on the front of our jewellery pieces than on the back. The principle could be compared to dropping fifty pound notes from a plane. If we drop ten thousand of them over a square kilometre in London, they will enrich the individual citizens less than if we drop ten thousand of them over a square kilometre in the Cotswolds. In the Cotswolds there are fewer people and therefore more money for each person than in London.

Similarly, the smaller surface of metal on the front of our jewellery gets a richer deposit of ions than the large surface on the back. An exacerbating factor is that electricity likes to flow to sharp or pointed sources of an opposite charge -- like lightning to a lightning rod. Consequently, our relatively sharp small wires attract far more electrical current and ion flow than the basically flat plain back of our jewellery.

The way we overcame this problem in nickel plating was just to put it back in and plate some more. If we plated long enough, the backs would eventually get bright. Of course the small wires on the front would be getting more buildup of nickel metal, but it was nice and bright and if a little thick, rarely unattractively so.

However, as nice as nickel was, circumstances alter cases. Last issue we explained that because the European Community ruled banning the presence of nickel in any item worn next to the skin, we now had a new row to hoe -- nickel free. We chose a course outlined to us by an experienced supplier which meant plating bright acid copper followed by silver followed by palladium followed by gold. But the heart of nickel free plating was a bath to replace the nickel's brightening ability which for us was to be bright acid copper.

When we started plating bright copper, we faced the same problem we had faced with nickel. But sticking it back in, which worked for nickel, didn't work here. Yes, eventually the backs got bright, but with that the small wires on the front and the edges were becoming rough and therefore not shiny. Thus we discovered that the parameters of copper plating were a lot tighter than nickel. So it looked like we were going to have to face a compromise between having bright backs and rough fronts or dull backs and bright fronts. It wasn't a very palatable compromise, because the market wasn't going to pat us on the back for having tried hard. Buyers of jewellery generally are concerned with the product they see, not the struggle the manufacturer has gone through to meet some regulations.

The EC's edict gave us some grace time to switch to nickel free. Ideally we would not have wanted to wait for that deadline to be in compliance, but now it looked as if we needed whatever grace was available. An idea we had was to continue to use nickel to achieve a uniform brightness and then to go to the bright copper, silver, palladium and gold on top of that. The hope was that the outer nickel free layers would create enough of a barrier over the nickel to pass the EC's nickel emission test. The jewellery looked nice that way and actually we have later learned that some people have managed to do that, but our hope turned out to be just that, a hope. The nickel test failed and so did my hope of finding an easy out.

I had always felt God wouldn't let us fail, that He would give us ideas that would win, but where were they now? They must be hidden deeper in the chemistry of that copper solution or in some part of my technique that we had not yet got down to.

I never entertained the idea of giving up, but I certainly didn't know where to go next. What was the next step? We will try to answer that next issue.

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