A combination of vinegar and hydrogen peroxide works with nickel-copper and is very safe. This is often used to etch PCBs. Using a few volts with the wire as cathode should also load H2. The muriatic may work better on Nitinol.
This is not precise calorimetry - Terry. you can to call it "thermometry" and be sure to stir. Just a simple way to gauge the comparative ability to raise the temp of a known mass of water. Using the specific heat to arrive at joules and logging the P-in, you can get a ballpark but the basic idea is comparative between a wire that may be slightly gainful and one that may be slightly endothermic. The idea is to see if there is anything "obvious" there, before incurring the expense and time of doing it right. For instance, going from 25C to 75C in an hour with Constantan at (x)watts P-in vs. 25 C to 65 C with Nitinol (both wires of the same Ohmic resistance) and everything else being the same . that would be interesting enough to dig deeper, no? Ahern's finding of anomalous endotherm with nickel-titanium is 'out there' in the public record and ought to be corroborated or debunked. From: Jack Cole I could run some low power electrolysis for a day or two in some diluted hydrochloric acid. Think that would do the trick? Or do you have another idea for the acid? Hydrogen loading will surely be necessary at some level, but can possibly be accommodated by combination of low pH electrolyte, not so low as to dissolve the wires. or preferably by preloading etched wires for a day under H2 pressure and modest heat, or even the simplest expedient which would be during a slow electro-etching in weak acid- with the wires as cathodes. The last would be the easiest to try for anyone without H2.
