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Hydrogen embrittlement while gold plating NiTi material

We are experiencing hydrogen embrittlement while gold plating NiTi material. The problem is that the embrittlement is very inconsistent. Approximately 5-20% of the parts out of a lot of 50 pieces. have hydrogen embrittlement. Any advise?

David Blauvelt
- Santa Ana, California, USA
2003

It would be nice to know what type of part you are working on. Something is wrong to have that level of failure. We need to know your entire process to make educated guesses. I would have thought that that metal would suffer from intergranular corrosion more than it would from H2 embrittlement. I would test a few parts with no treatment, then test some of the same lot (different parts) after each step of your processing. This should isolate the offending step. Normally, the absolute worst offender in hydrogen embrittlement is the acid etch/pickle. The plating is a relatively small offender. I assume that you are post plate bake for embrittlement relief. Try a preplate bake. It is necessary in some cases. A vacuum furnace would sure be nice so that you did not have to leave the parts in the acid as long. You may need to tumble the parts to mechanically remove any heavy oxides.

James Watts
- Navarre, Florida
2003

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David,

We also plate gold directly on nitinol, and must pass a crimp test. While I will not ask your preplate cycle and I will not tell you mine, watch your acid ratios. The cyanide plating process is also a source of H2 pick up as titanium is a "getter." James is right post bake ASAP. 375F 4 hour min. I can run samples if you wish to compare.

Jon Quirt
- Minneapolis, Minnesota
2003