"Aluminum as a substrate to plate onto"

Plating can only build successfully, and with good adhesion, onto a clean raw metal base, not onto an oxidized surface -- but aluminum is an extremely active metal which oxidizes instantaneously.

Thus, plating onto aluminum must be done by first "immersion plating / replacement plating" it with zinc from a highly concentrated solution of caustic soda and dissolved zinc. This process is called "zincating". Then we can electroplate onto the zinc layer.

Please search the site for "zincating".