You don't get "rusty" alloys. Alloys don't rust.
What is rust but oxidization
Rust: A reddish- or yellowish-brown flaking coating of iron oxide that is formed on iron or steel by oxidation, especially in the presence of moisture. Source Oxford English Dictionary.
I'll grant that rust is oxidisation but oxidisation on alloys is not rust. Just being pedantic.
You should be able to get rim completely bead blasted and painted or powdercoated for that
That is exactly what We Restore Alloys, who did mine, do. They remove the wheels from the car, remove the tyres from wheels, strip wheels right back, true the wheels up if necessary, repair any damage, chemically clean the wheels, powder coat them to a colour of your choice (some finishes are a bit more expensive), replace the tyres (using new valves) using a rubberised machine that prevents damage, inflate using Nitrogen, balance the wheels using adhesive weights on the inside faces only, then refit the wheels to the car so that tyres are in exactly the same position and orientation. Whole job had the car with them for two days. Did a lovely job and I was thrilled with the results. From having to top up the tyre pressures every fortnight I never had to add anything for the next two years I owned the car.
http://www.werestorealloys.co.uk/