Adhesion promoter for 2K aqueous epoxy systems to increase adhesion to metal substrates and corrosion resistance. BYK-4513 is used in aqueous epoxy-based coating systems as an adhesion promoter for metal substrates. It increases the wet and dry adhesion and the mechanical resilience, and can also help to improve the corrosion resistance of the coating. The polymeric character of BYK-4513 and its attachment to the metal-coating interface also provide more flexibility to the film coating. BYK-4513 is silane free and has outstanding storage stability. Recommended for protective coatings and also suitable for industrial coatings.