Aromatic 2-hydroxy-oximes as corrosion inhibitors for aluminium and zinc pigments

Both aluminium and zinc pigments react in aqueous alkaline media (e.g., water-borne paints) by the evolution of hydrogen, but the course of the respective corrosion reactions differs significantly. With the addition of three aromatic 2-hydroxy-oximes, aluminium and zinc pigments reacted completely differently. The overall corrosion inhibiting effect of the three examined oximes was significantly better for aluminium (protection factors up to 99.9%) than for the zinc pigment, as can be explained with Pearson's "Principle of Hard and Soft Acids and Bases". Furthermore, it was assumed, that the isoelectric point of aluminium and zinc oxide is an important factor controlling corrosion inhibition. (C) 1998 Elsevier Science Ltd. All rights reserved.