BYK 4509 is a adhesion promoter that creates strong affinity to metallic substrates and improves adhesion to materials like steel, galvanized steel and aluminum. BYK 4509 contains acidic groups that react with resins and polyisocyanates, binding it into polymer matrices. It provides universal compatibility with most binders and can be used in both aqueous and solvent-borne systems. BYK 4509 promotes adhesion in baking and multi-component coating systems, having no effect on cross-linking in acid-catalyzed solvent systems. It also shows very good pH stability in aqueous formulations. BYK 4509 is particularly suitable for industries that require durable, long-lasting coatings on metallic materials as it enhances adhesion of coating layers to substrates.