Galvanic Coupling of Doped Polyaniline and Aluminum Alloy 2024-T3

Abstract

The galvanic interaction between electronically conductive polyaniline films doped with camphor sulfonic acid (PAni-CSA), and aluminum alloy (AA) 2024-T3 has been investigated for the purpose of assessing PAni-CSA as a corrosion protection coating on AAs. Potentiodynamic polarization and zero resistance ammeter measurements of galvanic couples between PAni-CSA and AA 2024-T3 in 3.5% NaCl show that the AA dominates the mixed potential response and polarizes the PAni-CSA to approximately the potential of the freely corroding alloy (Ϫ0.54 V vs. Ag|AgCl). This observation indicates that conductive PAni coatings on Al are rapidly reduced to the nonconductive form on immersion in an aqueous electrolyte. The results also suggest that any corrosion protection of Al by PAni coatings is due to the barrier properties of the reduced polymer rather than anodic stabilization of passivity as observed with ferrous alloys. Mechanisms by which a PAni-CSA coating might provide corrosion protection of exposed 2024-T3 at defects in the coating are discussed.

The electrochemical deposition of polyaniline at pure aluminium: electrochemical activity and corrosion protection properties

“…Under these conditions the polymer will act only as a barrier coating, in agreement with the conclusions reached by Cogan et al [33]. It is likely that in the presence of the chloride anions, that some of the tosylate anions are exchanged with the chloride anions and these migrate to the aluminium substrate causing dissolution of the substrate.…”

“…Other authors have observed a similar galvanic interaction [13,33]. For example, Cogan et al [33] have concluded from their measurements of galvanic couples between polyaniline doped with camphorsulfonic acid and AA 2024-T3 that the alloy dominates the mixed potential response and polarizes the polyaniline to values near the potential of the freely corroding alloy, indicating that the conducting polyaniline coatings are reduced to the nonconductive form.…”

“…For example, Cogan et al [33] have concluded from their measurements of galvanic couples between polyaniline doped with camphorsulfonic acid and AA 2024-T3 that the alloy dominates the mixed potential response and polarizes the polyaniline to values near the potential of the freely corroding alloy, indicating that the conducting polyaniline coatings are reduced to the nonconductive form. They have also suggested that any corrosion protection of the alloy by the polyaniline is due to the barrier properties of the reduced polymer.…”

Electrosynthesis of Polyaniline Film on AA 7075 Alloy and Its Corrosion Protection Ability

“…6 The ES form of PANI oxidizes the aluminum surface as Due to this reaction, the conducting state of PANI is changed to the nonconducting state upon exposure to the NaCl solution. 26 However, in the present study, the PANI coating is able to protect nearly 70% due to the presence of cracks in the film.…”

Utilização de polianilina como revestimento protetor contra corrosão das ligas de alumínio 2014 F, 2024 T3 e 7075 O

“…Cogan et al [56] apresentam curvas de polarização para AA-2024-T3 com comportamento semelhante apresentado neste trabalho, todavia, nesse caso, as amostras foram imersas em NaCl 3,5% por uma hora antes de serem realizadas as curvas de polarização. Os dados acima estão em concordância com os apresentados na literatura, como os de Andreatta et al [57], que realizaram curvas de polarização anódica para a liga AA-7075 no mesmo meio.…”