Plating on Tellurium Copper Alloys

In my March column, I addressed a question regarding the plating of tellurium copper alloys. One of our readers emailed and said I “got it all wrong.” After reviewing my response, I agree that his suggested method is better than the one I suggested.

I always appreciate feedback from our readers, so keep your comments, suggestions and corrections coming.

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Here is the original question followed by this reader’s suggested procedure:

Q. I cannot achieve uniform adhesion of either Wood’s nickel or cyanide copper on C14500, tellurium-bearing copper. I clean using reverse current, followed by 11percent HCl, a Wood’s nickel strike, and a silver strike. After stripping the failed plate and repeating the process I sometimes have much better adhesion. Is this due to the aggressive etch provided by the stripping process or better oxide removal provided by the process? T.I.

A. Plating on beryllium and tellurium containing alloys always gives platers problems. The formation of oxides on the surface prevents good adhesion. The stripping of the defective plate likely gives you a better, cleaner surface for plating.

The procedure below gives successful results in many situations:

1. Alkaline clean. Electroclean would be better.
2. Dip in a 5 percent sulfuric acid solution.
3. Strike in a copper sulfate solution containing no organic additives.
4. Wood’s nickel strike.
5. Silver strike.
6. Silver plate.