Stabilization of Aluminum Pigment in Waterborne Paints

By Bodo Müller, Claude Oughourlian, Dimitrios Triantafillidis

Lamellar aluminum pigments (“aluminum flakes”) have been used in solventborne metallic paints or inks for many years. Waterborne metallic basecoats are used especially in the automotive industry to reduce the emission of organic solvents to the atmosphere during paint application.¹ Organic binders for waterborne paints usually contain carboxyl groups and have to be neutralized to salts by amines to become water-soluble or water-dispersible.

Therefore, the pH values of waterborne paints are about 8.¹ One of the problems with waterborne metallic basecoats is the corrosion reaction of the aluminum pigment with the alkaline aqueous paint medium, which causes the formation of hydrogen (detailed studies of the corrosion reactions of different types of aluminum pigments have been presented elsewhere2,3):