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Diffusion of platinum plating into metal substrate

In reference to the procedure described in US patent 4240878 (can be viewed best using pat2pdf.org), platinum black is plated onto a tantalum substrate, then the item is baked in an inert atmosphere to facilitate some diffusion of the plating into the surface of the substrate, creating a very tough coat. My question is, if I use tungsten instead of tantalum for the substrate, will a similar result be achieved, or would I have to modify the baking procedure (and how)? Thanks in advance for any help.

Borislav Trifonov
hobbyist, researcher - Vancouver, BC, Canada
2007

That probably will depend on the end use of the part. Tantalum is a very unique metal, namely, it can maintain strength at very high temperatures.

James Watts
- Navarre, Florida
2007

The intended use is as plasma electrodes in air, in a microhollow cathode setup (insulator is sapphire wafer). The platinum plating is necessary to prevent the tungsten from simply burning up. I do have some worry of the opposite, i.e. too much diffusion so that it continues during actual use of the parts. I've also considered rhodium plating but I'm not sure that would not just crack and fall off due to differential expansion when heated. The electrodes will be heatsinked, but right at the ~1 mm diameter microhollows the temperature would still approach the melting point of platinum.

Borislav Trifonov
- Vancouver, BC, Canada
2007