Mechanism of Action of Corrosion Protection Coating for AA2024-T3 Based on Poly(aniline)-Poly(methylmethacrylate) Blend

• Published in: Journal of the Electrochemical Society 2005, Vol.152 (2), p.B45-B53
• Main Authors: Seegmiller, Jesse C., Pereira da Silva, José E., Buttry, Daniel A., Córdoba de Torresi, Susana I., Torresi, Roberto M.
• Format: Article
• Language: English
• ISSN: 0013-4651
• DOI: 10.1149/1.1839472

A corrosion protection coating for AA2024-T3 composed of a blend of camphorsulfonate-doped poly(aniline) (PANT) and poly(methylmethacrylate) (PMMA) is described. The open-circuit potential (OCP) for the bare and coated alloy in H2SO4 solutions is presented vs. time. Raman spectroscopy revealed the oxidation state of the PANT component of the blend, both on undamaged films and as a function of distance away from a scratch on purposefully damaged films. The open-circuit and Raman data show galvanic coupling between the coating and the alloy, causing reduction of the PANT component. Scanning electrochemical microscopy was used to monitor H2 evolution over a scratch on the surface of either PANT blend or PMMA films coated on AA2024. These experiments show that the scratched surface is highly active toward H2 evolution when coated with only a PMMA film. In contrast, the blend coating drastically suppresses the amount of H2 evolution in a scratch. This suppression of H2 evolution was mimicked by poising the OCP of the PMMA-coated alloy at the same value at which it is poised by the PANT-containing film. It is shown that camphorsulfonate anion has no inhibitory effect on H2 evolution in scratches on PMMA-coated AA2024.