There is lots of info on this topic on the Samba. From my research of front suspensions many suggest powder coating the beam, but painting the rods. One issue/concern with powder coating is chipping. Unlike painted surfaces, it cannot be "repainted" once chipped. Is your friends car on the road and being driven? Or is he putting his beam together and it has startred to flake? If the latter the prep work or the powder coating may not have done properly.