right then, first of all you should be able to spay any surface that has been prepared properly, however if you are planning to have the item powdercoated it's best to remove the anodising first,if this item has been hard anodised as you would expect if it's a frame, you're going to find it difficult to remove without scratching the frame, this could leave a visible mark afterwards, you could take the frame to an anodising/plating firm who can dip the frame into a chemical which removes the anodising and have it re-anodised or powdercoated elsewhere, the chemical process used to strip anodised items can however leave a rough finish which would affect a re-anodised finish so it's advisable to powdercoat or polish the item before re-anodising, hope that helps, best of luck. 😀