I buy my chemicals from the supplier of my ultrasonic machine, they have one called ferrocarb for removing paint and rust from steel & cast iron and another chemical for alloy, but it's industrial grade stuff.
There's also quite a bit of difference in power output between smaller home machines and the larger industrial types. Our larger unit is 150L and has some pretty serious power (and makes a hell of a noise) but I don't know if smaller 3L / 1L would do it or not - I suppose there's no harm in trying.
I can chase down the SDS for the ferrocarb solution if you'd like to see what's in it.
