Polymeric corrosion inhibitors for copper and brass pigments

Copper and brass pigments corrode in aqueous alkaline media with the absorption of oxygen that can be measured gasvolumetrically. These corrosion reactions can be inhibited by certain polymers; the metallic sparkle and the color of the pigments is preserved. The brass pigment is inhibited more effectively than the copper pigment. Some low-molecular mass styrene-maleic acid (SMA) copolymers are efficient corrosion inhibitors; a low acid number is necessary but not sufficient for corrosion inhibition. At pH 8.5 there is a potential correlation between the acid number of the low-molecular mass SMA and the oxygen volumes absorbed from brass pigment dispersions; oxygen volumes decrease with decreasing acid number. Furthermore, increasing copolymer addition effects an increase of corrosion inhibition. Polyacrylic acids, polyvinyl alcohols and high-molecular mass SMA copolymers are ineffective. The most efficient group of polymers examined in this study are the styrene-acrylate copolymers because by addition of these the overall lowest volumes of oxygen were absorbed by the metal pigments. (C) 2001 John Wiley & Sons, Inc.