If you can find the 'right' chemical solution, it might be salvageable. Solution would need to remove the alum corrosion, but not affect steel & brass parts.
i think part of the problem is that the corrosion has actually compromised the the piece past the point of salvage.
i had a situation with an old italian motorbike that kept having fuel related problems. no amount of cleaning the tank, tap, carb, jets, anything would solve it for more than a few days. then right back to a bunch of junk in the bowl and a no start. it turns out that the bowl had been compromised and was corroding and as fuel would evaporate the alum oxide would form, then when you turned on the tap the fuel would wash down all the alum oxide and it would basically make a slurry in the bowl. because the oxide wasn't allowed to fully harden off, it didn't form a new protective layer over the compromised aluminum so it was just a vicious cycle.
