Selective etchant for Al2O3 (Does not etch Al, Cu, Zn, Sn)
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