The electrodeposition of polyaniline-polypyrrole composite coatings on aluminium was successfully performed by using cyclic voltammetry. Oxalic acid was used as the electrolyte. Electrodeposition was carried out at a scan rate of 20 mV/s by varying the number of cycles. An anodic peak current at around -0.1 V versus saturated calomel electrode (SCE) was observed in the cyclic voltammograms. This peak is due to the oxidation and adsorption of hydrogen. The cyclic voltammograms also show another anodic peak current at around 1.0 V versus SCE, which is the characteristic peak of the polyaniline-polypyrrole composite. The behavior of this peak with respect tu the number of cycles is discussed in detail. A corresponding cathodic peak current at around -0.7 V versus SCE was also observed in the cyclic voltammograms. The infrared spectra of the composite coatings revealed the infrared peaks of both polypyrrole and polyaniline, The scanning electron micrographs of the coatings indicate a morphology completely different from its homopolymers.