Copolymers as corrosion inhibitors for different metal pigments

摘要

The base aluminium and zinc pigments corrode in aqueous alkaline media with the evolution of hydrogen whereas the more noble copper and brass pigments react with the absorption of oxygen. Both types of corrosion reactions can be examined gasvolumetrically. The corrosion reactions of all examined metal pigments can be inhibited more or less by addition of styrene-maleic acid-acrylate copolymers with different acrylate monomers (ethyl- n-butyland n-hexylacrylate as well as n-dodecyl- and n-octadecylmeth-acrylate). A surprising result is that the oxygen corrosion of the brass pigment is inhibited more effectively by the copolymers when compared to the copper pigment. With respect to the interaction of the metals with the copolymers there are two groups of metal pigments. The first group is aluminium pigment only; the corrosion inhibiting effect of the copolymers increases with increasing side chain length of the acrylate monomer. The second group consists of the base zinc pigment and the more noble copper pigment; the corrosion inhibiting effect of the copolymers decreases with increasing side chain length of the acrylate monomer. These connections between the chemical composition of the copolymers and their corrosion inhibiting effect can be correlated mathematically with the help of potential functions.