Saturday, November 15, 2025
Probe 7 - Looks Different To The Rest
Probes etched in nitric acid tended to have a short, stumpy tip with rough sided. I'd found that adding hydrochloric acid to the salt etch removed cloudy precipitates, but the concentration I used was way lower than with nitric acid. So I etched Probe 7 using 50ml of 0.5% hydrochloric acid and 2 grams of salt. I also reduced the submerged length of the probe wire to 6mm.
The etch released noticeably more gas on the cathode, and the etched wire broke off just below the meniscus. For scale, that's a 0.3mm diameter 316 stainless wire:
I'm constantly surprised at the variations produced by merely changing the etching electrolyte. Good job I'm using a consistent electrolysis rig or I'd wonder what they heck was going on.
Again, the actual tip on this one is sharper than I intended. I was expecting it to have a more rapid taper like the nitric acid etched ones. However, it looks like it might be a very robust geometry, so I'm going to test it anyway. Time to mount yet another probe tip, which is much easier now I have the printed jig and less likely to result in probe destruction.
