Electrochemical polymerization of polypyrrole coatings on hard-anodized coatings of the aluminum alloy 2024-T3

Abstract

Electrochemical polymerization was used to produce over-oxidized polypyrrole coatings on hard-anodized coatings of the aluminum alloy 2024-T3. Alumina surfaces with an average thickness of 4 ± 0.22 μm were studied. Solutions of 0.5 M H2SO4 and 0.5 M pyrrole at 5 °C and vigorous stirring were used to obtain the polymeric coatings. A pulsed potential condition and the equivalent continuous potential condition were used to obtain polypyrrole coatings, and the results were compared. The coating obtained using the pulsed potential had good adhesion because the percentage of polymer removed was less than 5%, based on the standard (ASTM D3359-17). In addition, the coating obtained using the pulsed potential had a more homogeneous appearance than the coating obtained using the continuous potential condition. The ON potential of 15 V vs. a saturated calomel electrode overcame the resistance to electric charge transfer of the hard-anodized coatings, making the electrochemical polymerization possible, although the polypyrrole coatings were over-oxidized. In addition, the polypyrrole coating obtained using a pulsed potential defined a new and small resistance to electric charge transfer on the hard-anodized surface, which could have been related to the conductive properties of the polymer.