Moog NOW has balljoints for al. Arms - but they are more expensive than the ones for steel.
bead blasting would be a good thing - seals the surface. If powdercoating al. Arms is possible or wise, you have to ask a professional powder coater.
Although the A-Arms dont get "much" damaged by the corrosive winter stuff, more in danger are all other steel and painted stuff down there.
Sway bar, struts, bolts, nuts and so on.