Anticorrosion performances of epoxy coatings modified with polyaniline: A comparison between the emeraldine base and salt forms

The protection against corrosion imparted by epoxy paints modified by the addition of polyaniline emeraldine base (0.3% w/w) and Zn-3(PO4)(2) (10% w/w) has been investigated and compared. For this purpose, accelerated assays through corrosion cycles, which simulate the marine conditions, have been performed using a home-made robotized equipment. Results were compared with those recently obtained for a formulation constituted by the same epoxy paint modified with polyaniline emeraldine salt (0.3% w/w) [E. Armelin, R. Pla, E Liesa, X. Ramis, J.I. Iribarren, C. Aleman, Corr. Sci. 50 (2008) 721.]. A detailed analysis of the results using the ASTM standard method D-1654-79 allows to conclude that the coating modified with polyaniline emeraldine base performs better than both the unmodified coating and the coatings modified with the inorganic corrosion inhibitors. This behaviour should be attributed to a mechanism based on the ability of polyaniline emeraldine base to store charge. On the other hand, as the epoxy paint modified with the latter polymer provides better results than the formulation containing Zn-3(PO4)(2), we conclude that inorganic corrosion inhibitors, which may have detrimental effects on both the environment and the human health, can be replaced by a small concentration of environmentally friendly organic polymers. (C) 2008 Elsevier B.V. All rights reserved.