i.e. is it possible to avoid the wet etch attack on an Aluminum layer where also Silver (or gold) are present and need to be etched?
Due to a presence of a thin layer of aluminium oxide onto the Al surface, the latter is subjected to a passivation in conc. HNO3 and H2SO4. It is very important to perform this reaction using the cold acids.
On the other hand Ag can react with conc. and cold HNO3.
For Au it is possible the following reaction
Au+NaCN (KCN) + O2 +H2O = Na[Au(CN)2]+NaOH
This reaction is also appropriate for Ag.
It is seems that concentration of formed NaOH will be insufficient for the reaction with aluminum.
hope u can try ammonical thiosulphate leaching
https://www.researchgate.net/publication/284725714_Gold_dissolution_in_non-ammoniacal_thiosulphate_solutions_comparison_of_fundamentals_and_leaching_studies
https://www.researchgate.net/publication/223186258_Gold_and_silver_extraction_by_ammoniacal_thiosulfate_leaching_from_a_rhyolite_ore
Conference Paper Gold dissolution in non-ammoniacal thiosulphate solutions: c...
Article Gold and silver extraction by ammoniacal thiosulfate leachin...
In a generic alloy of Al/Ag is it reasonable to attack selectively only the silver?
seems quite difficult... you can try with some mild nitric acid in presence of hydrogen peroxide or sodium nitrate in higher pH...
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