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10/1/2000

Tellurium Copper Problems

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Question: We are trying to plate silver over nickel on tellurium copper.

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Question:

We are trying to plate silver over nickel on tellurium copper. We are having problems with peeling. When we plate beryllium copper parts we do not have this problem. Can you help us? P.S.

Answer:

Tellurium tends to have many of the same properties as beryllium. The only significant difference seems to be that tellurium copper requires a more aggressive preparation cycle. There are a number of recommended methods. One such method is to pretreat the parts in hot concentrated caustic followed by pickling in 30–60% nitric acid (v/v). Sometimes you can get by without the hot caustic step. Keep in mind that hot caustic is nasty stuff and must be thoroughly removed before going to the nitric acid dip.

Another approach is to use an acid dip prepared from phosphoric acid (38–40%), nitric acid (2%) and acetic acid (58–60%). A temperature of 160F is recommended. The nitric acid concentration tends to control the rate of oxide removal.

Because tellurium copper requires a more aggressive cycle, you may have to use the solution above for a longer period of time or at a slightly higher temperature.

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