Stabilization of Aluminum Pigments in Aqueous Alkaline Media by Styrene Copolymers

By Bodo Müller

Aluminum pigments react in alkaline aqueous media (e.g., waterborne metallic paints) with the evolution of hydrogen. Low- and high-molecular weight styrene-maleic acid copolymers inhibit the corrosion of aluminum pigments in a mixture of water and butyl ether of ethylene glycol at a pH value of 10 very effectively and are much better corrosion inhibitors than high-molecular weight polyacrylic acids or a styrene-acrylic acid copolymer.

There is a correlation between the composition of the styrene-maleic acid copolymers and the evolved hydrogen volume: the lower the acid number the lower the hydrogen volume—resulting in a higher corrosion inhibiting effect.