If I wanted to preserve old spokes just for the heckuvit, I'd try Oxpho Blue liquid and fine steel wool. It's a cold blue formula for guns but will work on any carbon steel. It's very effective at converting rust to a form that won't spread and continuing to eat away at metal. Simple and it works. But it will darken shiny carbon steel and the surface may appear mottled with some steels.

Otherwise, CLR (Calcium-Lime-Rust remover, spray or liquid) and Scotchbrite pads.