Selective etchant for Al2O3 (Does not etch Al, Cu, Zn, Sn) I'm looking for a wet-etchant to remove aluminum oxide created by anodizing, but not etch the unoxidized metal (with greater than 10:1 selectivity)

I know about chromium(IV) oxide and fluorine-based etchants, but those are problematic for safety and disposal. Are there other etchants? It can be an acid or a base.
In Fabrication of Microstructures by Wet Etching of Anodic
Aluminum Oxide Substrates Chem. Mater. 2005, 17, 4049-4052,

5% phosphoric acid is used and is selective relative to aluminum, but you need to check how it would do with respect to the other metals you mention


  Finally, the AAO substrate was wet-etched in a 5 wt % H3PO4 solution
  at 20 °C for 8 h