Zinc pigments and waterborne paint resins

Zinc pigments corrode in aqueous alkaline paint media (e.g., waterborne anticorrosive paints) with the evolution of hydrogen. Paint resins inhibit this corrosion reaction at a pH value of 8 more effectively than at pH10. An increase of resin addition effects a decrease of hydrogen evolution (i.e., corrosion inhibition increases). The corrosion reaction of spherical zinc dust can be nearly completely inhibited with the addition of a certain epoxy ester resin (EPE 1). The epoxy ester resin looses its corrosion inhibiting properties after film formation, because of loosing its mobility, which seems to a be requirement for corrosion inhibition. So, zinc dust is inhibited in the liquid waterborne paint but still shows its sacrificial action in the solid primer coating.