Polypyrrole coatings on aluminum — synthesis and characterization

The electrodeposition of polypyrrole coatings on aluminum was carried out by cyclic voltammetry using oxalic acid as the electrolyte. The cyclic voltammograms show an anodic peak at around 0.0 V vs. SCE for very high scan rates (750 mV/s) at shorter cycles. With the increase in number of cycles (>10), the presence of this peak is no longer visible. This peak is related to the adsorption and oxidation of hydrogen. At shorter scan rates (50 mV/s), the length of time where the deposition of polypyrrole on the aluminum substrate takes place is much longer, and so the amount of polymer deposited in one cycle, is correspondingly more. The anodic peak at around 0.0 V vs. SCE was no longer visible after the first cycle in the cyclic voltammograms. The infrared spectroscopy of the coatings indicates that polypyrrole is in the doped form. The scanning electron micrographs show microspheroidal morphology of polypyrrole.