Powder Coated Black Screens.
Powder coating is an industrial process that produces a hard wearing, long lasting, UV resistant surface.
After thorough cleaning, the screens are electrostatically charged and then sprayed with a fine dusting of black polyester polymer which clings to the charged surface. The screens are then baked in a 400F degree oven that melts the powder and when cooled, forms a hard, stable finish resistant to UV and corrosion that is much tougher then conventional liquid paint. 
The advantage of a powder coated black screen is that it tends to disappear when looking out portlights and will not discolor and corrode as unfinished bronze and copper will. The Black screens look particularly sharp in Chrome plated ports. 
Black, Powder coated screens are in stock only for
Pacific SeaCraft Rectangular

sail boat port light insect screens