Copper and brass pigments corrode in aqueous alkaline media with absorption of oxygen which can be measured gasvolumetrically. These corrosion reactions can be inhibited by certain copolymers, the metallic sparkle and the colour of the pigments being preserved. The brass pigment (rich gold) is inhibited more effectively by copolymers than the copper pigment. The corrosion inhibiting effect of styrene-maleic acid-acrylic ester copolymers on copper pigment decreases with increasing the chain length of the ester alcohol of the acrylate monomer. The most effective copolymer examined in this study is the styrene-maleic acid-ethyl acrylate copolymer which inhibited the corrosion reactions of copper and brass pigment both at pH 8.5 and 10.
Müller, B., & Schubert, M. (1999). Corrosion inhibition of copper and brass pigments in aqueous alkaline media by copolymers. Progress in Organic Coatings, 37(3), 193–197. https://doi.org/10.1016/S0300-9440(99)00079-X