Dear Enosh

Chromic acid bath, which can be made by careful dissolving of potassium chromate in H2SO4, might be suitable. Check Google for the preparation of this solution and take some causion!!

There is a commercial preparation called “nochromix” that is useful - uses persulfate as the oxidizer I believe. A little tamer than the “piranha” solution of H2SO4 and H2O2.

Dear all, one simple tip is the backflow introduction of any available digestion solution, such as diluted HF and Piranha. My Regards

Hi

Yes you can with HCl 3%