Is it possible to strip and powder coat fork lowers?

Not sure what they’re made of, they are 2006 reba race 29ers if that makes a difference?

They’re white but I want black!

You’d need to remove the bushes first to powder coat them, as they are baked.
I’d just rub them down & use Platikote.
Goes on thick, with decent shine.

Or get a car body shop to do them.

thats not a bad plan, there’s little value to them anyway so might be worth going the spray can route.