When painting Durabak onto bare metal surfaces it is hard for the Durabak to form a strong bond with the metal, the most important think to ensure a strong adhesion is a very thorough roughing up of the bare metal with a 40 grit sandpaper. Use primer, like this Zinc Phosphate to seal the metal, almost like galvanizing it, to treat against rust etc.
Moeller Zinc Primer Aerosol Spray works great on aluminum surfaces above or below the waterline. This power primer etches into the aluminum, forming a strong surface/primer union that is resistant to corrosion. Choose the color that contrasts least with the topcoat you intend to apply over the primer.
For steel and iron surfaces, especially welded joints, use Zinc Phosphate. This corrosive barrier contains a high percentage (95%) of zinc, for maximum resistance against solvents & abrasions.
Available in a 12 oz aerosol spray can.