It is highly recommended to apply an epoxy barrier coat directly to the aluminum below the waterline to form a protective coating. The primary reason to apply a barrier coat to aluminum below the waterline is corrosion resistance. After applying the barrier coat, apply a copper-free antifouling paint that is safe for use on aluminum boats, such as Interlux Trilux 33, TotalBoat Krypton, Pettit ECO HRT, or Sea Hawk Smart Solution AF.