I've baked enamael paints onto components. The idea is similar to pro- car metal and even copper enamaeling.
I did 120 degrees for 20 min, 3 coats. in the oven.
Glassed up good, took a major knock with a pointed metal to chip out.
Cheapest enamael worked best??? Generic 'Colorall' seeemed to work really well.
The metal has to be 'prepared' to have paint (sanding, cleaning)
An idea anyway. I don't know enough about post cast heat treatment of Alu to go for cranks tho- that would require some reaserch.