I would think that painted spokes would eventually shed the paint just from flexing during use
I've tried it, & yes they eventually do;I polished them first,which was a mistake.
Cadmium,zinc? plating may be cost effective,although I've never personally done it at home.
I saw a YouTube on it once and it mentioned glass bead blasting them prior to soaking them in the cadmium. I watched them 'do it yourself' coating the spokes at home,but it's been a while.
I would rather get used,OEM spokes coated compared to buying cheap china spokes..