Near me is a company that makes diving boards- the aluminum ones used in the olympics. What, with salt water pools, and pool chemicals in the rest, corrosion is a given!
They use an epoxy paint on the boards; other hardware is "hard anodized."
Perhaps you can find a shop in your area willing to do either? While epoxy can be in any color, the "hard anodize" color is completely dependent on the aluminum alloy, and may come out blagk, grey, or even a dark 'army' green.