HIGH-MOLECULAR-WEIGHT STYRENE-MALEIC ACID COPOLYMERS AS CORROSION-INHIBITORS FOR ALUMINUM PIGMENTS

High-molecular weight styrene-maleic acid copolymers inhibit the corrosion of aluminium pigments in a mixture of water and butyl glycol at a ratio 9:1 at a pH value of 10 very effectively (protection factors up to 99%). This was proved by volumetric measurement of the corrosion product hydrogen. High-molecular weight polyacrylic acids are much less effective corrosion inhibitors for aluminium pigments. There is a dependence between the content of carboxyl groups of the copolymers and the evolved volume of hydrogen: the lower the acid number of the copolymers the lower is the evolved volume of hydrogen. Measurement of the concentration of dissolved aluminium(III) by atomic absorption spectroscopy showed the formation of at least partially soluble copolymer-aluminium (III) complexes.