Corrosion inhibition of aluminium and zinc pigments by saccharides

Both aluminium and zinc pigments react in aqueous alkaline media (e.g., water-borne paints) with the evolution of hydrogen which can be measured gas volumetrically. The hydrogen corrosion of aluminium pigment can be inhibited with addition of the reducing saccharides fructose and mannose as well as with addition of the reducing ascorbic acid whereas the non-reducing saccharose did not inhibit this corrosion reaction. With increasing addition of fructose or ascorbic acid the hydrogen volumes evolved increase; this observation leads to the assumption that reaction products of aluminium and fructose or ascorbic are the actual corrosion inhibitors. The hydrogen corrosion of zinc pigment is inhibited by ascorbic acid only. So, the most efficient of the examined natural corrosion inhibitors both for aluminium and zinc pigment is ascorbic acid. But corrosion inhibition of ascorbic acid on zinc pigment is much less effective when compared to aluminium. (C) 2002 Elsevier Science Ltd. All rights reserved.